Original source · versioned page text
Geotechnical Report
LINDSAY CONSULTING PTY LTD -
STRUCTURAL AND CIVIL ENGINEERS
ACN 079 744 808 ABN 61 478 386 385 GST REGISTERED
AS TRUSTEE FOR THE LINDSAY FAMILY TRUST
Ref: 231061
16th November 2023
Pools by Design
Attn Gary,
GEOTECHNICAL INVESTIGATION FOR
PROPOSED POOL
5 SEAMIST COURT, SUNSHINE BEACH
We have been engaged to carry out a Geotechnical Stability Review for the above
project. The purpose of the review is to
• Identify existing soil types and profiles,
• Determine existing soil parameters for the proposed development,
• Evaluate site conditions and any affect these site conditions have on the
proposed development, and
• Comment on the Geotechnical Slope Stability of the allotment, existing and post
construction.
Standards and references used in carrying out the Geotechnical Stability Review include
but are not limited to the following:-
• AS 1289 - Methods of testing Soils for Engineering Purposes
• AS 1726 - Geotechnical Site Investigations
• AS 2870 - Residential Slabs and Footings – Construction
• AS 3798 - Guidelines on Earthworks for Commercial and Residential
developments
• Australian Geomechanic Society Practice Note Guidelines for Landslide Risk
Management 2007
• Lindsay Consulting Pty Ltd Design Drawings 231061--PL1 to PL3 inclusive
• Lindsay Consulting Pty Ltd site classification report 231061
METHOD AND SCOPE OF INVESTIGATION
Fieldwork for the investigation was carried out by Lindsay Consulting Pty Ltd staff
using a truck mounted drill rig with additional testing carried out by hand. Samples of
soils from the site were taken to Lindsay Consulting Pty Ltd’s laboratory and tested in
accordance with the applicable standards.
QUALIFICATIONS OF COMPANY AND COMPETENT PERSONS
Staff utilized in the preparation of the work includes Mr. Jason Lindsay (RPEQ 4928) a
Civil Engineer whom has worked as a Civil, Structural, and Geotechnical engineer since
1990 performing geotechnical evaluation during his employment with John Wilson and
Partners Tewantin Office which was attached to the John Wilson and Partners Soils and
Off. 2C/82 Parker St, Maroochydore 4558
OFFICE: (07) 54 792 118 MOBILE: 0412 313 645 FAX: (07) 54 510 118
E-MAIL: [email protected]
See the original
The page text is free to read. Viewing or downloading an original file needs an account.
Log in to see the originalLog in to download the original file
The download may take up to a minute.
Full text of the other 38 pages
Page 2
LINDSAY CONSULTING PTY LTD - STRUCTURAL AND CIVIL ENGINEERS ACN 079 744 808 ABN 61 478 386 385 GST REGISTERED AS TRUSTEE FOR THE LINDSAY FAMILY TRUST Materials Laboratory. In his over 30 year experience Mr. Lindsay has carried out over ten thousand site and soil evaluations including site classifications in accordance with AS2870 and geotechnical evaluations for stability on many of these sites. Field work is carried out by Mr Nathan McFadden in accordance with the above Australian Standards. Mr Fadden has worked in the engineering field as a soil and site evaluator or over 15 years, the last 9 years with Lindsay Consulting. Previously Mr McFadden worked for a NATA registered laboratory carrying out field and laboratory testing to NATA approved standards for major and minor civil work projects SITE GEOLOGY From the borelogging carried out over the site (refer attached Site Classification Report) the site consists of a consists of peat/clayey sand, overlying sand loose becoming dense with depth. The residence is located on dunal area above the Dolphin Bay reserve with the area falling from the residence towards the reserve. The area to the rear of the residence is heavily treed with a heavy undergrowth. Off. 2C/82 Parker St, Maroochydore 4558 OFFICE: (07) 54 792 118 MOBILE: 0412 313 645 FAX: (07) 54 510 118 E-MAIL: [email protected]
Page 3
LINDSAY CONSULTING PTY LTD - STRUCTURAL AND CIVIL ENGINEERS ACN 079 744 808 ABN 61 478 386 385 GST REGISTERED AS TRUSTEE FOR THE LINDSAY FAMILY TRUST Off. 2C/82 Parker St, Maroochydore 4558 OFFICE: (07) 54 792 118 MOBILE: 0412 313 645 FAX: (07) 54 510 118 E-MAIL: [email protected]
Page 4
LINDSAY CONSULTING PTY LTD - STRUCTURAL AND CIVIL ENGINEERS ACN 079 744 808 ABN 61 478 386 385 GST REGISTERED AS TRUSTEE FOR THE LINDSAY FAMILY TRUST Off. 2C/82 Parker St, Maroochydore 4558 OFFICE: (07) 54 792 118 MOBILE: 0412 313 645 FAX: (07) 54 510 118 E-MAIL: [email protected]
Page 5
LINDSAY CONSULTING PTY LTD - STRUCTURAL AND CIVIL ENGINEERS ACN 079 744 808 ABN 61 478 386 385 GST REGISTERED AS TRUSTEE FOR THE LINDSAY FAMILY TRUST No groundwater was observed during the testing or inspection of the site, however, possible seasonal water tables or seepage may be possible along the unweathered rock layer. STABLITY CONSIDERATIONS The level of excavation intended over the site leads Lindsay Consulting Pty Ltd to believe that the stability of the site will be suitable for this type of construction. There were no signs of instability on the allotment. The location of the pool on this slope does not in our opinion lead us to believe that slope stability will be a concern. DUE TO THE NATURE OF THE SITE, ORGANIC PEAT MATERIAL OVER LOOSE SANDS LINDSAY CONSULTING PTY LTD RECOMEND THE PROVISION OF SCREW PILES INTO THE DENSE SAND MATERIALS UNDER. A landslip Hazard Frequency analysis has been carried out for the site and the proposed works, refer Appendix E, and we conclude there is a low risk of site instability with the pool located in its proposed location. The low risk of instability as defined in the guidelines in the attached appendix does not exclude slope stability problems, only that in Lindsay Consulting Pty Ltd’s opinion that the risk is low and may be management through good hillside practises. In our professional opinion, the present site conditions along with the proposed earthworks detailed on the drawings specified previously do not pose a slope stability issue with the site including associated buildings and infrastructure and that the stability of the site will be maintained during both the construction and operational life of the development. As such the works proposed, when carried out in a capable manner will not lead to a slope stability problem. Lindsay Consulting Pty Ltd further certifies that at the time of this report there were no signs of stability issues with adjoining lands and as such the site is not subject to risk of landslip activity originating from these other land. Lindsay Consulting Pty Ltd clarify this statement in that any adjoining works or changes to existing works on adjoining lands must be carried out in a professional manner and in accordance with good hillside practices so as to not affect the stability of the adjoining land which may inturn affect the stability of the subject allotment. Should you require any further information please do not hesitate to contact me at the above address. On and Behalf of LINDSAY CONSULTING PTY LTD Jason Lindsay RPEQ Off. 2C/82 Parker St, Maroochydore 4558 OFFICE: (07) 54 792 118 MOBILE: 0412 313 645 FAX: (07) 54 510 118 E-MAIL: [email protected]
Page 6
LINDSAY CONSULTING PTY LTD -
STRUCTURAL AND CIVIL ENGINEERS
ACN 079 744 808 ABN 61 478 386 385 GST REGISTERED
AS TRUSTEE FOR THE LINDSAY FAMILY TRUST
APPENDIX A – ENGINEERING DESIGN DRAWINGS
AND SOIL TEST
Off. 2C/82 Parker St, Maroochydore 4558
OFFICE: (07) 54 792 118 MOBILE: 0412 313 645 FAX: (07) 54 510 118
E-MAIL: [email protected]
Page 7
LINDSAY CONSULTING PTY LTD -
STRUCTURAL AND CIVIL ENGINEERS
ACN 079 744 808 ABN 61 478 386 385 GST REGISTERED
AS TRUSTEE FOR THE LINDSAY FAMILY TRUST
SITE CLASSIFICATION REPORT
JOB NUMBER 231061
CLIENT POOLS BY DESIGN
SITE LOCATION No. 5 SEAMIST COURT, SUNSHINE BEACH
REPORT DATE NOVEMBER 2023
1. INTRODUCTION
The purpose of this report is to classify the subject allotment in accordance with
Australian Standard 2870-2011 'Residential Slabs and Footings. From this classification
a footing system has been recommended for the structure so as to allow adequate
performance of the footings under the soil conditions determined at the site.
This report relates exclusively to the proposed pool at subject allotment, as detailed on
the architectural drawings supplied by the client. This document has been prepared for
the express purpose stated above. This document does not cover any other elements
related to construction on the site.
2. SITE DESCRIPTION
The subject allotment is a residential lot fronting a sealed road, there is an existing
residence at the site and the proposed pool is to be located towards the rear. The
proposed site has average grass cover with dense undergrowth and many shrubs and
small trees present, the site falls towards the rear of the block at an approximate slope
of 15%.
3. SOIL PROFILE
The borelogs carried out at the site, refer attached Site Plan for localities, indicate that
the soil profile consists of clayey sand (high organic content - peat) overlying silty sand.
A WATERTABLE was encountered at the time of testing at a depth of 900mm.
Whilst every effort has been made to ensure that the borelogs carried out at the subject
allotment are indicative of the soil profile over the site any discrepancy between the
profile detailed in the borelogs and that observed during construction shall be referred
to the Consulting engineer for immediate attention.
4. MATERIALS LABORATORY TEST RESULTS
Determination of the classification for the site in this situation is based upon test results
from Dynamic Cone Penetrometer testing performed over the site and shrink/swell test
results.
Off. 2C/82 Parker St, Maroochydore 4558
OFFICE: (07) 54 792 118 MOBILE: 0412 313 645 FAX: (07) 54 510 118
E-MAIL: [email protected]
Page 8
5. SITE CLASSIFICATION AND TARGET STRATA
Based on the findings of the site investigation and the footing system design proposed
on the client supplied information, the classification of the site is considered to conform
to: -
CLASS " P "
This classification is due to poor bearing capacity of the existing soil and
the presence of peat.
However, if this was not the case the soil type and reactivity would
be comparable to that of a CLASS " M ".
in accordance with Australian Standard 2870-2011, 'Residential Slabs and Footings,
Construction'.
An allowable bearing capacity of 100kPa is reached with the medium dense SILTY
SAND which occurs at a depth of 1200mm from the existing ground level at location
BH1 and at a depth of 1300mm at location BH2. Any fill placed over the existing
ground shall be piered through the fill into the existing material. Further note that the
placement of reactive material as fill may change the site’s classification.
6. FOOTING SYSTEM DESIGN
The footing system shall be designed to conform to the performance limits stated in AS
2870 – 2011 and reprinted in the C.S.I.R.O.'s Publication 10/91, 'Guide to Home
Owners on Foundation Maintenance and Footing Performance', a copy of which
attached to this report. It should be noted that footings designed in accordance with
AS2870-2011 does not guarantee no movement of footings, shrinkage cracking or other
damage to the building.
Foundation preparation and footing construction shall be in accordance AS 2870 -2011
and AS 3798-1990 'Guidelines on Earthworks for Commercial and Residential
Developments'.
Where necessary, subsoil drainage shall be incorporated in the construction of the
building to ensure that subsurface water is properly drained away from the footings.
Potential seepage or subsoil drainage problems cannot always be recognised from the
results of a site investigation. Problems with respect to subsurface water flow or
seepage may not be evident until after the site has been subject to the first significant
wet period.
After construction of the footing system the ground surface around the residence shall
be sloped away from the footings at a fall of 1 in 20 minimum for a distance of 2000
mm.
7. ARTICULATION
It is recommended that masonry walls on Class M, H, E and P sites be articulated at all
or some openings. Articulation joints shall be constructed in accordance with the
Cement and Concrete Association's Publication 'TN61 - Articulated Walling'.
Page 9
8. SERVICES
Expansive or collapsing soils require special considerations at service connections to
ensure flexibility to prevent damage or breakage. In areas where known expansive or
collapsing soils are present flexible connections and impervious plugs shall be provided
to all services including all drainage, stormwater and septic system.
On and Behalf of
LINDSAY CONSULTING PTY LTD
Jason Lindsay
RPEQ 4928
Page 10
LIMITATIONS Recommendations given in this report are based on the information supplied by the client regarding the proposed building construction in conjunction with the findings of the investigation. Any change in construction type, building location or omission in the client supplied information, may require additional testing and/or make the recommendations invalid. The recommendations herein identify a target soil stratum into which the footings are to be founded. The target stratum has been located by the depth in mm of the target stratum's upper horizon boundary below the existing ground surface level at the time of the site investigation. Any cutting or filling works and any surface erosion or deposits subsequent to the site investigation, will alter the measured location of the stratum relative to the surface. Where required, the author should be notified in such cases to confirm the location of the target stratum. The description of the soil given in the Soil Profile section of this report is intended as a brief overview of the soil's primary constituents. For a detailed classification of the soil, the reader should refer to the Soil Profile Reports and/or Borehole Reports attached to this report. Every reasonable effort has been made to locate the test sites so that the borehole profiles are representative of the soil conditions within the area investigated. The client should be made aware however, that exploration is limited by time available and economic restraints. In some cases soil conditions can change dramatically over short distances, therefore, even careful exploration programs may not locate all the variations. If soil conditions different from those shown in this report are encountered or are inferred from other sources, then the author must be notified immediately. This report may not be reproduced except in full. The information and drawings provided with this report shall only be used and will only be applicable for the development shown on the client supplied information provided for this site. Any dimensions, contours, slope directions and magnitudes shown on the Test Locality Plan shall not be used for any building construction or costing calculations. The purpose of the plan is to show approximate location of field tests only. Any changes made to these recommendations by persons unauthorised by the author will legally be interpreted as that person assuming the responsibility for the long-term performance of the footing system. The recommendations contained in this report have not taken into consideration the long term effects of any previous, current or potential subsurface work by mining companies or potential slope instability problems. At the time of writing this report neither our client (nor his agent) nor the local authority had made the author aware that these problems may be affecting this allotment. If a mining subsidence or slope stability assessment is required for this allotment, the recommendations of a suitably qualified geotechnical engineer should be sought.
Page 11
Foundation Maintenance and Footing Performance: A Homeowner's Guide (i) CSIRO BIF 18 replaces Information Sheet 10/91 Buildings can and often do move. This movement can be up, down, lateral or rotational. The fundamental cause of movement in buildings can usually be related to one or more problems in the foundation soil. It is important for the homeowner to identi the soil type in order to ascertain the measures that should be put in place in order to ensure that problems in the foundation soil can be prevented, thus protecting against building movement. This Building Technology File is designed to identify causes of soil-related building movement, and to suggest methods of prevention of resultant cracking in buildings. Soil Types The types of soils usually present under the topsoil in land zoned for residential buildings can be split into two approximate groups — granular and clay. Quite often, foundation soil is a mixture of both types. The general problems associated with soils having granular content are usually caused by erosion. Clay soils are subject to saturation and swell/shrink problems. Classifications for a given area can generally be obtained by application to the local authority, but these are sometimes unreliable and if there is doubt, a geotechnical report should be commissioned. ‘As most buildings suffering movement problems are founded on clay soils, there is an emphasis on classification of soils according to the amount of sweil and shrinkage they experience with variations of water content. The table below is Table 2.1 from AS 2870, the Residential Slab and Footing Code. Causes of Movement Settlement due to construction There are two types of settlement that occur as a result of construction: * Immediate settlement occurs when a building is first placed on its foundation soil, as a result of compaction of the soil under the weight of the structure. The cohesive quality of clay soil mitigates against this, but granular (particularly sandy) soil is susceptible. * Consolidation settlement is a feature of clay soil and may take place because of the expulsion of moisture from the soil or because of the soil’s lack of resistance to local compressive or shear stresses. This will usually take place during the first few months after construction, but has been known to take many years in excuptlonal sen These problems are the province of the builder and should be taken into consideration as part of the preparation of the site for construc- tion. Building Technology File 19 (BTF 19) deals with these problems. Erosion All soils are prone to crosion, but sandy soil is particularly susceptible to being washed away. Even clay with a sand component of say 10% or more can suffer from erosion. Saturation This is particularly a problem in clay soils. Saturation creates a bog- like suspension of the soil that causes it to lose virtually all of its bearing capacity. To a lesser degree, sand is affected by saturation because saturated sand may undergo a reduction in volume — particularly imported sand fill for bedding and blinding layers. However, this usually occurs as immediate settlement and should normally be the province of the builder. Seasonal swelling and shrinkage of soil All clays react to the presence of water by slowly absorbing it, making the soil increase in volume (see table below). The degree of increase varies considerably between different clays, as does the degree of decrease during the subsequent drying out caused by fair weather periods. Because of the low absorption and expulsion rate, this phenomenon will not usually be noticeable unless there are prolonged rainy or dry periods, usually of weeks or months, depending on the land and soil characteristics. The swelling of soil creates an upward force on the footings of the building, and shrinkage creates subsidence that takes away the support needed by the footing to retain equilibrium. Shear failure This phenomenon occurs when the foundation soil does not have sufficient strength to support the weight of the footing. There are ewo major post-construction causes: * Significant load increase. * Reduction of lateral support of the soil under the footing due to crosion or excavation. * In clay soil, shear failure can be caused by saturation of the soil adjacent to or under the footing. GENERAL DEFINITIONS OF SITE CLASSES Class Foundation A Most sand and rock sites with little or no ground movement from moisture changes s Slightly reactive clay sites with only slight ground movement from moisture changes M Moderately reactive clay or silt sites, which can experience moderate ground movement from moisture changes H Highly reactive clay sites, which can experience high ground movement from moisture changes E Extremely reactive sites, which can experience extreme ground movement from moisture changes AtoP Filled sites Pp Sites which include soft soils, such as soft clay or silt or loose sands; landslip; mine subsidence; collapsing soils; soils subject to erosion; reactive sites subject to abnormal moisture conditions or sites which cannot be classified otherwise
Page 12
Tree root growth ‘Trees and shrubs that are allowed to grow in the vicinity of footings can cause foundation soil movement in two ways: * Roots that grow under footings may increase in cross-sectional size, exerting upward pressure on footings. * Roots in the vicinity of footings will absorb much of the moisture in the foundation soil, causing shrinkage or subsidence. | Unevenness of Movement The types of ground movement described above usually occur unevenly throughout the building's foundation soil. Settlement due to construction tends to be uneven because of: * Differing compaction of foundation soil prior to construction. * Differing moisture content of foundation soil prior to construction. Movement due to non-construction causes is usually more uneven still. Erosion can undermine a footing that traverses the flow or can create the conditions for shear failure by eroding soil adjacent to a footing that runs in the same direction as the flow. Saturation of clay foundation soil may occur where subfloor walls create a dam that makes water pond. It can also occur wherever there is a source of water near footings in clay soil. This leads to a severe reduction in the strength of the soil which may create local shear failure. Seasonal swelling and shrinkage of clay soil affects the perimeter of the building first, then gradually spreads to the interior. The swelling process will usually begin at the uphill extreme of the building, or on the weather side where the land is flat. Swelling gradually reaches the interior soil as absorption continues. Shrinkage usually begins where the sun’s heat is greatest. _Effects of Uneven Soil Movement on Structures Erosion and saturation Erosion removes the support from under footings, tending to create subsidence of the part of the structure under which it occurs. Brickwork walls will resist the stress created by this removal of support by bridging the gap or cantilevering until the bricks or the mortar bedding fail. Older masonry has little resistance. Evidence of failure varies according to circumstances and symptoms may include: * Step cracking in the mortar beds in the body of the wall or above/below openings such as doors or windows. * Vertical cracking in the bricks (usually but not necessarily in line with the vertical beds or perpends). Isolated piers affected by erosion or saturation of foundations will eventually lose contact with the bearers they support and may tilt or fall over. The floors that have lost this support will become bouncy, sometimes rattling ornaments etc. Seasonal swelling/shrinkage in clay Swelling foundation soil due to rainy periods first lifts the most exposed extremities of the footing system, then the remainder of the perimeter footings while gradually permeating inside the building footprint to lift internal footings. This swelling first tends to create a dish effect, because the external footings are pushed higher than the internal ones, The first noticeable symptom may be that the floor appears slightly dished. This is often accompanied by some doors binding on the floor or the door head, together with some cracking of cornice mitres. In buildings with timber flooring supported by bearers and joists, the floor can be bouncy. Externally there may be visible dishing of the hip or ridge lines. As the moisture absorption process completes its journey to the innermost areas of the building, the internal footings will rise. If the spread of moisture is roughly even, it may be that the symptoms will temporarily disappear, but it is more likely that swelling will be uneven, creating a difference rather than a disappearance in symptoms. In buildings with timber flooring supported by bearers and joists, the isolated piers will rise more easily than the strip footings or piers under walls, creating noticeable doming of flooring. Seer ee Sd (eu) mS ROLL Wall cracking due to uneven footing settlement As the weather pattern changes and the soil begins to dry out, the external footings will be first affected, beginning with the locations where the sun’s effect is strongest. This has the effect of lowering the external footings. The doming is accentuated and cracking reduces or disappears where it occurred because of dishing, but other cracks open up. The roof lines may become convex. Doming and dishing are also affected by weather in other ways. In areas where warm, wet summers and cooler dry winters prevail, water migration tends to be toward the interior and doming will be accentuated, whereas where summers are dry and winters are cold and wet, migration tends to be toward the exterior and the underlying propensity is toward dishing. Movement caused by tree roots In general, growing roots will exert an upward pressure on footings, whereas soil subject to drying because of tree or shrub roots will tend to remove support from under footings by inducing shrinkage. Complications caused by the structure itself Most forces that the soil causes to be exerted on structures are vertical — i.e. either up or down. However, because these forces are seldom spread evenly around the footings, and because the building resists uneven movement because of its rigidity, forces are exerted from one part of the building to another. The net result of all these forces is usually rotational. This resultant force often complicates the diagnosis because the visible symptoms do not simply reflect the original cause. A common symptom is binding of doors on the vertical member of the frame. Effects on full masonry structures Brickwork will resist cracking where it can. It will attempt to span areas that lose support because of subsided foundations or raised points. It is therefore usual to see cracking at weak points, such as openings for windows or doors. In the event of construction settlement, cracking will usually remain unchanged after the process of settlement has ceased. With local shear or erosion, cracking will usually continue to develop until the original cause has been remedied, or until the subsidence has completely neutralised the affected portion of footing and the structure has stabilised on other footings that remain effective. In the case of swell/shrink effects, the brickwork will in some cases return to its original position after completion of a cycle, however it is more likely that the rotational effect will not be exactly reversed, and it is also usual that brickwork will settle in its new position and will resist the forces trying to return it to its original position. This means that in a case where swelling takes place after construction and cracking occurs, the cracking is likely to at least partly remain after the shrink segment of the cycle is complete. Thus, each time the cycle is repeated, the likelihood is that the cracking will become wider until the sections of brickwork become virtually independent. With repeated cycles, once the cracking is established, if there is no other complication, it is normal for the incidence of cracking to stabilise, as the building has the articulation it needs to cope with the problem. This is by no means always the case, however, and monitoring of cracks in walls and floors should always be treated seriously. Upheaval caused by growth of tree roots under footings is not a simple vertical shear stress. There is a tendency for the root to also exert lateral forces that attempt to separate sections of brickwork after initial cracking has occurred.
Page 13
The normal structural arrangement is that the inner leaf of brick- work in the external walls and at least some of the internal walls (depending on the roof type) comprise the load-bearing structure on which any upper floors, ceilings and the roof are supported. In these cases, it is internally visible cracking that should be the main focus of attention, however there are a few examples of dwellings whose external leaf of masonry plays some supporting role, so this should be checked if there is any doubr. In any case, externally visible cracking is important as a guide to stresses on the structure generally, and it should also be remembered that the external walls must be capable of supporting themselves. Effects on framed structures Timber or steel framed buildings are less likely to exhibit cracking due to swell/shrink than masonry buildings because of their flexibility. Also, the doming/dishing effects tend to be lower because of the lighter weight of walls. The main risks to framed buildings are encountered because of the isolated pier footings used under walls. Where erosion or saturation cause a footing to fall away, this can double the span which a wall must bridge. This additional stress can create cracking in wall linings, particularly where there is a weak point in the structure caused by a door or window opening. It is, however, unlikely that framed structures will be so stressed as to suffer serious damage without first exhibiting some or all of the above symptoms for a considerable period. The same warning period should apply in the case of upheaval. It should be noted, however, that where framed buildings are supported by strip footings there is only one leaf of brickwork and therefore the externally visible walls are the supporting structure for the building. In this case, the subfloor masonry walls can be expected to behave as full brickwork walls. Effects on brick veneer structures Because the load-bearing structure of a brick veneer building is the frame that makes up the interior leaf of the external walls plus perhaps the internal walls, depending on the type of roof, the building can be expected to behave as a framed structure, except that the external masonry will behave in a similar way to the external leaf of a full masonry structure. Water Service and Drainage Where a water service pipe, a sewer or stormwater drainage pipe is in the vicinity of a building, a water leak can cause erosion, swelling or saturation of susceptible soil. Even a minuscule leak can be enough to saturate a clay foundation. A leaking tap near a building can have the same effect. In addition, trenches containing pipes can become watercourses even though backfilled, particularly where broken rubble is used as fill. Water that runs along these trenches can be responsible for serious erosion, interstrata seepage into subfloor areas and saturation, Pipe leakage and trench water flows also encourage tree and shrub roots to the source of water, complicating and exacerbating the problem. Poor roof plumbing can result in large volumes of rainwater being concentrated in a small area of soil: * Incorrect falls in roof guttering may result in overflows, as may gutters blocked with leaves etc, * Corroded guttering or downpipes can spill water to ground. * Downpipes not positively connected to a proper stormwater collection system will direct a concentration of water to soil that is directly adjacent to footings, sometimes causing large-scale problems such as erosion, saturation and migration of water under the building. Seriousness of Cracking In general, most cracking found in masonry walls is a cosmetic nuisance only and can be kept in repair or even ignored. The table below is a reproduction of Table C1 of AS 2870. AS 2870 also publishes figures relating to cracking in concrete floors, however because wall cracking will usually reach the critical point significantly earlier than cracking in slabs, this table is not reproduced here. | Prevention/Cure Plumbing Where building movement is caused by water service, roof plumbing, sewer or stormwater failure, the remedy is to repair the problem. It is prudent, however, to consider also rerouting pipes away from the building where possible, and relocating taps to positions where any leakage will not direct water to the building vicinity. Even where gully traps are present, there is sometimes sufficient spill to create erosion or saturation, particularly in modern installations using smaller diameter PVC fixtures. Indeed, some gully traps are not situated directly under the taps that are installed to charge them, with the result that water from the tap may enter the backfilled trench that houses the sewer piping. If the trench has been poorly backfilled, the water will either pond or flow along the bottom of the trench. As these trenches usually run alongside the footings and can be ata similar depth, it is not hard to see how any water that is thus directed into a trench can easily affect the foundation's ability to support footings or even gain entry to the subfloor area. Ground drainage In all soils there is the capacity for water to travel on the surface and below it. Surface water flows can be established by inspection during and after heavy or prolonged rain. If necessary, a grated drain system connected to the stormwater collection system is usually an easy solution. It is, however, sometimes necessary when attempting to prevent water migration that testing be carried out to establish watertable height and subsoil water flows. This subject is referred to in BTF 19 and may properly be regarded as an area for an expert consultant. Protection of the building perimeter Ic is essential to remember that the soil that affects footings extends well beyond the actual building line. Watering of garden plants, shrubs and trees causes some of the most serious water problems. For this reason, particularly where problems exist or are likely to occur, it is recommended that an apron of paving be installed around as much of the building perimeter as necessary. This paving CLASSIFICATION OF DAMAGE WITH REFERENCE TO WALLS Description of typical damage and required repair Approximate crack width Damage limit (see Note 3) category Hairline cracks <0.1 mm 0 Fine cracks which do not need repair <l mm 1 Cracks noticeable but easily filled. Doors and windows stick slightly <S mm 2 Cracks can be repaired and possibly a small amount of wall will need 5-15 mm (or a number of cracks 3. to be replaced. Doors and windows stick. Service pipes can fracture. 3 mm or more in one group) ‘Weathertightness often impaired Extensive repair work involving breaking-out and replacing sections of walls, 15-25 mm but also depend 4 especially over doors and windows. Window and door frames distort. Walls lean on number of cracks or bulge noticeably, some loss of bearing in beams. Service pipes disrupted
Page 14
Clump of trees;
1 height selected
% for distance
Saal Paint Ln from house
poe fertile
nage erator" BEIM Ye ene pm Mh
poeta fn Narn tegatana)
SS eee ST ri GL
meyer TTT
ee Patio.
{UHH
—| Drained
Carport pathway
Path—@
Garden bed
P _—— covered with
Driveway et mulch
fraternal
should extend outwards a minimum of 900 mm (more in highly
reactive soil) and should have a minimum fall away from the
building of 1:60. The finished paving should be no less than 100
mm below brick yent bases.
Ic is prudent to relocate drainage pipes away from this paving, if
possible, to avoid complications from future leakage. If this is noc
practical, earthenware pipes should be replaced by PVC and
backfilling should be of the same soil type as the surrounding soil
and compacted to the same density.
Except in areas where freezing of water is an issue, it is wise to
remove taps in the building area and relocate them well away from
the building — preferably not uphill from it (see BTF 19).
It may be desirable to install a grated drain at the outside edge of the
paving on the uphill side of the building. If subsoil drainage is
needed this can be installed under the surface drain.
Condensation
In buildings with a subfloor void such as where bearers and joists
support flooring, insufficient ventilation creates ideal conditions for
condensation, particularly where there is little clearance between the
floor and the ground. Condensation adds to the moisture already
present in the subfloor and significantly slows the process of drying
out. Installation of an adequate subfloor ventilation system, either
natural or mechanical, is desirable.
Warning: Although this Building Technology File deals with
cracking in buildings, it should be said that subfloor moisture can
result in the development of other problems, notably:
+ Water that is transmitted into masonry, metal or timber building
elements causes damage and/or decay to those elements.
¢ High subfloor humidity and moisture content create an ideal
environment for various pests, including termites and spiders.
* Where high moisture levels are wansmitted to the flooring and
walls, an increase in the dust mite count can ensue within the
living areas. Dust mites, as well as dampness in general, can be 2
health hazard to inhabitants, particularly those who are
abnormally susceptible to respiratory ailments.
The arden
The ideal vegetation layout is to have lawn or plants that require
only light watering immediately adjacent to the drainage or paving
edge, then more demanding plants, shrubs and trees spread out in
that order.
Overwatering due to misuse of automatic watering systems is a
common cause of saturation and water migration under footings. If
ir is necessary to use these systems, it is important to remove garden
beds to a completely safe distance from buildings.
Existing trees
Where a tree is causing a problem of soil drying or there is the
existence or threat of upheaval of footings, if the offending roots are
subsidiary and their removal will not significantly damage the tree,
they should be severed and a concrete or metal barrier placed
vertically in the soil to prevent future root growth in the direction of
the building. If it is not possible to remove the relevant roots
without damage to the tree, an application to remove the tree should
be made to the local authority. A prudent plan is to wansplant likely
offenders before they become a problem.
Information on trees, plants and shrubs
State departments overseeing agriculture can give information
regarding root patterns, volume of water needed and safe distance
from buildings of most species. Botanic gardens are also sources of
information, For information on plant roots and drains, see Building
Technology File 17.
Excavation
Excavation around footings must be properly engineered. Soil
supporting footings can only be safely excavated at an angle that
allows the soil under the footing to remain stable. This angle is
called the angle of repose (or friction) and varies significantly
between soil types and conditions. Remoyal of soil within the angle
of repose will cause subsidence.
Where erosion has occurred that has washed away soil adjacent to
footings, soil of the same classification should be introduced and
compacted to the same density. Where footings have been
undermined, augmentation or other specialist work may be required.
Remediation of footings and foundations is generally the realm of a
specialist consultant.
Where isolated footings rise and fall because of swell/shrink effect,
the homeowner may be tempted to alleviate floor bounce by filling
the gap that has appeared between the bearer and the pier with
blocking. The danger here is that when the next swell segment of the
cycle occurs, the extra blocking will push the floor up into an
accentuated dome and may also cause local shear failure in the soil.
Ifit is necessary to use blocking, it should be by a pair of fine
wedges and monitoring should be carried out fortnightly.
This BTF was prepared by John Lewer FAIB, MIAMA, Partner,
Construction Diagnosis.
The information in this and other issues in the series was derived from various sources and was believed to be correct when published.
The information is advisory. It is provided in good faith and not claimed to be an exhaustive treatment of the relevant subject.
Further professional advice needs to be obtained before taking any action based on the information provided.
Distributed by
CSIRO PUBLISHING PO Box 1139, Collingwood 3066, Australia
Freecall 1800 645 051
Tel (03) 9662 7666 Fax (03) 9662 7555 www.publish.csiro.au
Email: [email protected]
© CSIRO 2003. Unauthorised copying of this Building Technology file is prohibited
Page 15
SITE PHOTOGRAPHS
Page 16
Lindsay Consulting Pty Ltd
Off. 2C/82 Parker Street, Maroochydore
NO. 5 SEAMIST COURT,
CLIENT POOLS BY DESIGN SITE LOCATION
SUNSHINE BEACH
REFERENCE 231061
BORELOG 1 BORELOG 2 PENETROMETERS
Depth Depth
below below
Group Group
ground Soil Description ground Soil Description PN1 PN2 PN3 PN4 PN5
Symbol Symbol
level level
(mm) (mm)
0 SC Clayey SAND, fine to medium, dark grey, 0 SC Clayey SAND, fine to medium, dark grey,
high plasticity fines, moist, soft (HIGH high plasticity fines, moist, soft (HIGH
100 ORGANIC CONTENT-PEAT) 100 ORGANIC CONTENT-PEAT) 0.25 0.25
200 200 0.25 0.25
300 300 0.25 0.25
400 400 0.25 0.25
500 500 0.3 0.3
600 600 0.3 0.3
Silty SAND, fine to medium, pale grey,
700 SM low plasticity fines, moist, loose 700 Silty SAND, fine to medium, pale grey, 0.3 0.3
800 800 SM low plasticity fines, moist, loose 0.5 0.5
WATERTABLE WATERTABLE
900 SM Silty SAND, fine to medium, pale grey, 900 SM Silty SAND, fine to medium, pale grey, 0.5 0.5
low plasticity fines, saturated, loose low plasticity fines, saturated, loose
1000 1000 1 1
Hole Terminated – Collapsing
1100 Hole Terminated – Collapsing 1100 1 2
1200 1200 3 1
1300 1300 4 3
1400 1400 5 6
1500 1500 6 5
COMMENTS
AUTHORISED SIGNATORY
Page 17
Lindsay Consulting Pty Ltd
Off. 2C/82 Parker Street, Maroochydore
NO. 5 SEAMIST COURT,
CLIENT POOLS BY DESIGN SITE LOCATION
SUNSHINE BEACH
REFERENCE 231061
BORELOG 1 BORELOG 2 PENETROMETERS
Depth Depth
below below
Group Group
ground Soil Description ground Soil Description PN1 PN2 PN3 PN4 PN5
Symbol Symbol
level level
(mm) (mm)
0 SC Clayey SAND, fine to medium, dark grey, 0 SC Clayey SAND, fine to medium, dark grey,
high plasticity fines, moist, soft (HIGH high plasticity fines, moist, soft (HIGH
100 ORGANIC CONTENT-PEAT) 100 ORGANIC CONTENT-PEAT) 0.25 0.25
200 200 0.25 0.25
300 300 0.25 0.25
400 400 0.25 0.25
500 500 0.3 0.3
600 600 0.3 0.3
Silty SAND, fine to medium, pale grey,
700 SM low plasticity fines, moist, loose 700 Silty SAND, fine to medium, pale grey, 0.3 0.3
800 800 SM low plasticity fines, moist, loose 0.5 0.5
WATERTABLE WATERTABLE
900 SM Silty SAND, fine to medium, pale grey, 900 SM Silty SAND, fine to medium, pale grey, 0.5 0.5
low plasticity fines, saturated, loose low plasticity fines, saturated, loose
1000 1000 1 1
Hole Terminated – Collapsing
1100 Hole Terminated – Collapsing 1100 1 2
1200 1200 3 1
1300 1300 4 3
1400 1400 5 6
1500 1500 6 5
COMMENTS
AUTHORISED SIGNATORY
Page 18
LINDSAY CONSULTING ¢7;, fvjl Engineers) LTA ED 4928 OFF. 20/82 PARKER TREET, MAROQGAYDORE PH 5h 792 118 POOLS BY DESIGN PROPOSED POOL NO.5 SEAMIST COURT SUNSHINE BEACH CLIENT AND PROJECT DESCRIPTION SCALES REVISION LIST. > ORIGINAL ISSUE SURVEY DATUM THIS DRAWING REMAINS HE PROPERTY OF LINDSAY CONSULTING PTY LTD AND IS FOR THE SOLE USE OF THE CLIENT. NO PART MAY BE USED IN PART OR WHOLE WITHOUT PRIOR EXPRESS WRITTEN CONSENT OF LINDSAY CONSULTING PTY LTD DRAWING TITLE SITE PLAN ASSOCIATED CONSULTANTS [Computer Fite 231061SP.DWG DRAWING NUMBER 23-1061-S1 Bo st 4oomm Coping —— 2nd Storey house Steel columns NG Existing home ist Floor wors = o B 8 S ° mS — B s = S . a n bu an 2 ° < GRAVEL PIT Easement with HOUSE SEWER CONNECTION 4.00m
Page 19
EXISTING RESIDENCE LINDSAY CONSULTING PTY
LTD
LINDSAY CONSULTING HAVE NOT
BEEN PROVIDED WITH CONTOUR
SURVEY PLAN OR ACCURATE
LOCATION OF EASEMENT/SEWER
A SITE NOTE THAT THE FINAL LAYOUT, SHAPE AND SIZE SHALL BE
CONFORMED ON-SITE PRIOR TO CONSTRUCTION, DRAWN TO
INFORMATION PROVIDED BY CLIENT. LINDSAY CONSULTING DOES
NOT HOLD ANY RESPONSIBILITY FOR THE INFORMATION NOT
PROVIDED.
POOL FENCING IN ACCORDANCE WITH AS1926- 2007.
SELF LOCKING GATE LOCATIONS TO BE CONFIRMED ON-SITE
DECK BY OTHERS
POOL CONTRACTOR IS TO ENSURE THAT THE PROPOSED POOL IS
EITHER OUTSIDE THE TREE ZONE OF INFLUENCE OR PROVIDE APPROX 2.1 m OOG
PROTECTIVE MEASURES AGAINST THE TREE EFFECTS SUCH AS
INSTALLING ROOT BARRIER OR SIMILAR. TREE ZOI IS "DISTANCE
FROM TREE = TREE HEIGHT X 2.0". ALTERNATIVELY THE POOL
CONTRACTOR IS REQUIRED TO INFORM ENGINEER OF TREE
LOCATION AND HEIGHTS FROM POOL ALONG WITH A SOIL
REPORT TO DETERMINE THE SOIL EFFECTS APPLIED TO THE 1.2 m DEEP
POOL SHELL. THE POOL CONCRETE & REINFORCEMENT SHALL BE
APPROX EASEME
DESIGNED TO SUPPORT INCREASED SURFACE MOVEMENT Centre block wall to support pool
SEWER APPROX base without internal shell piers
NT- AS PROVIDE
600 Wide Strip footing as per details
1.8 m DEEP
900mm DEEP
D BY POOL BUILD
RED CIRCLES Indicate 120kN safe
working load screw piles. Install 1-S12
bars through the top of pile 1m long min
APPROX 2.7 m OOG
ER
Page 20
N16 corner bars @ 125 crs (Above Ground)
350mm min lap
Radius 155mm
LINDSAY CONSULTING PTY
LTD
WALL REINFORCEMENT AS PER
DETAILS
Page 21
$12 @ 150 CRS each way in base D VERTICAL BARS 1500 MAX S12 @ 300 crs 1800 MAX $12 Bars @ 300 crs S12 Intermediates @ 300 crs 200 D - 1800 mm MAX Water Level 500 f 1a} fo Vertical bars refer table. ———| $12 Horizontals @ 125 crs I. 75mm cover to inside of pool | ting beam 100 Max 4-S12 in 400 Radius min N12 [email protected] to pool base. r 450 min. lap. UNCONTROLLED GRAVEL BACKFILL NATURAL SURFACE | constaucridn 1400 MAX 3400 mm MAX OVERALL HEIGHT JOINT 190mm core filled blockwork with N12 @ 400 crs each|wa Lo y N12 starters/@ 400 CRS 450mm min. lap. LYAXYYAY AY | FO Screw Piles (120 kN SWL)) | SECTION THROUGH ABOVE GROUND POOL YPXYXRYDYILYYXY YY lt 600 x 600 footing with 4-N12 top and bottom R10 ligs at 200 CRS Screw Piles (120 kN SWL)) ed $12 bar through top of screw pile (1000 mm long) LINDSAY CONSULTING #7 CLI RPEO 4928 THIS DRAWING REMAINSAHE PROPERTY OF LINDSAY CONSULTING PTY LTD AND IS FOR THE SOLE USE OF THE CLIENT. NO PART MAY BE USED IN PART OR WHOLE WITHOUT PRIOR EXPRESS WRITTEN CONSENT OF LINDSAY CONSULTING PTY LTD CLIENT AND PROJECT DESCRIPTION POOLS BY DESIGN PROPOSED POOL NO.5 SEAMIST CRT SUNSHINE BEACH DRAWING TITLE TYPICAL REINFORCEMENT DETAILS SCALES SURVEY DATUM ASSOCIATED CONSULTANTS REVISION LIST > ORIGINAL ISSUE 16/1723, [computer File 231061PL.DWG DRAWING NUMBER SHEET] REV. 23-1061-PL3 3A
Page 22
LINDSAY CONSULTING PTY LTD -
STRUCTURAL AND CIVIL ENGINEERS
ACN 079 744 808 ABN 61 478 386 385 GST REGISTERED
AS TRUSTEE FOR THE LINDSAY FAMILY TRUST
APPENDIX B –
PRACTICE NOTE GUIDELINES INTO LANDSLIDE
RISK MANAGEMENT
Off. 2C/82 Parker St, Maroochydore 4558
OFFICE: (07) 54 792 118 MOBILE: 0412 313 645 FAX: (07) 54 510 118
E-MAIL: [email protected]
Page 23
4002 YEW Lb ON Zr IA SojUBYDStUDeS Uel}EnSNYy
6
ksI9A 9214 10U “UDidL2S9G UBIsse OF UONdLOSSG 20 aBeuME Jo 1805 TeUNKeAddy Jsn TUBE or YOY Woy pasn_aq pInOYs sige 74L <b)
“Suadoid ayy ia2yye ABUL YAIYAS SOPHISPUEY 4942 SSUPPH 0} SOM HONESHLGMS |ELOLEPPE IPN|SuI I0U s90p Ip "UONEpouTEATe
Aseroduisi “saa; [eBO] se ORS sys0a yENUSNbosUOS PUL “SooJ UTISOpP [WUOISSQJOId PUY PaNs.O SEY YOIYM SpPHSpUE] IYI JOJ [PAD] YSU FIQeIDIOI O1 SIS 94) JOPUDS OF PaumNbas sys0ns
wonesipquys '(soamongys snyd puxl) Suadosd om yo uoruod paBeuep oi yo wuawoTeIstIA JO 1909 DY) Sv YONs “ABRUEp 941 JO SOD Jaap ayi fo BeuUNSS UN aq 0} St ISOD BeUunxouddy sq), tay
‘soamionas pasayeun
au sid pury otp sopnjam qonpw Ausdosd poroayeun ay) Jo anja paroudur ag) Jo 109 OM) Fu19q “onpRA yoyseuL Jo aFema2u0d w se passaadxa st aSeumg Jo oD oeuNxesddy 2y_ —(Z)_—=SMION
ti Casta 3: "930 Atepunog [euonou =
5 LNVOIINDISNI BP paplarpans aq seu GoTaws siyp (urea IsoWy) 12. iene Rar the tons mee apy SO
e ONDA SOM UONESHIqejs TEAMS estas SOs SULT para] el Ses
“SEeurEp s2Uanbosuos IOUT ALodosd jUsSEIpE Sue [Seal 1 ASHES P[noy *o0t ~
€ woidaw “Sym vONESI ACIS 826] SuuNbas ous Jo ued juvsy{UTIs 20/puE “AIMIINUNS 50 2WEs 0} aBvUP aIDPOW 207
“SauuiEp souanbasios winipow Avadoud jasEIpe SuO Sea] I SsNeS PINeD “SHO UORESTIqUIS ‘HO,
z MOV quwaryrudis TuMbas SoUpunog ay puosog Zurpuayxa 10 /pure “aunr9NAS Jo SOU! 01 DSeusup aatsua1xy %09
“SamaEp souonbasuos ioleu Auedoud jusoulpe suo Ise9] Te SsNUD Pinos “UoHUsTIqers OF :
t SIHdOMLSVLVD 40) Som BuysaurSus 2ofeur Subs: oFeuup sess Vue] 10/pue p2Xoxsep <jmo[dwoo (s)oamanns OE.
Saepunog, ae
peed andiassg aondusseg peworON aAneoipey
aBeurng jo ys0> PEuNxoaddy
ALUAATOUd OL SHINANOASNOD AO STANSVAW FALLVLITKAO
“‘PSJ9A SOTA YOU “JOIALDSIG] UBisse oO} UONNMISOG 40 AWyiquqolg jenuUY sRtUTxOIddy asn YysE OF Yd] WIOLY PoSN oq PINOYs Bqe) FL wD 290N
a Aiaidauo ATauva 301 USISOp Sip ISA [AFDUN) JO aIqUAISSUOSUT ST WANT AML | ean yogroue s189% 900 0001 aire 201
: 7 aH Usisap sy) Ao = eee
a ARIVY | ssouvisumoate jeuondaoxe iapun <juo ang apquasaouoa St 1UIAa AU, d aoo'ont I asia OL
aaassp | >< oon‘ = s
aq ATENEIND | ain saxo ssounistunaiio ssuape asa aapun snas0 jyStU yUAAe aU, s209% 900°0L Res Ol
> FIAISSOd | ai] Uaisap dq) JAA SUOHIPUOS SSIRAPS JDP MD PNG WADA AU, SHB9A WOOT SanDe OOOT ¥ oT
ee sxea 007 a cuss :
a ATU | 31 soso suomypucs asa2ape Jopun sna90_<iqeqosd qj. wad AULL xbsene aor te of
Vv. NVI 1SOWTV 2] UBISap ofp IAG INDO Or PaaadNa s] WDA SUL waeaA OF Sore
Siepaneg z
even] sendjaed oopeiansn pessayuy aouaasnoay reuonON 2aneopuy
, aPHSPEET Qaneaypuy poudiay Amqeqosg penuuy aearyxoaddy
GOOHTTANIT AO STUNSVAW AAILVLITFAO
ALYAdOUd OL MSRI ONISSASSV NI ASN AOU ADO TONIAMAL FALLVLITVNO
ANGAINSSASSY MSTA FATISAGNY'T *D XIGNGddVv
£002 LNSWS9VNVW MSI8 SQMSOGNVT YOS SANINAGINS 3LON ADILOVad
Page 24
4002 YEW | ON Zp OA SOIUEYDoWOSD UeYENSNY ce
“apingd [ex9uas v se uDAIS
ApGO aie asayy 2st Ie Aodoud ayy JO ounTeU ay) UO pusdop Keur pue waussasse ysLI Ip OF somsed [je Aq pouTUUaEp oq O} ase UONENpS sepNoIEd B 40} suoNRoIidun oy], {L) :30N
‘sounpasosd souvuajurems odojs jeauoU Aq aBeuepy ‘opquidsooy ASHI AOT AWA ‘TA
“‘palmbar
St aouEUDTUTeUE BULOTUO *]9A9| Sty) 0} YSU 9M SONpeL O12 poulnbos usaq sey UOULAN sD>y AA “SUOTEINBo2 O71 o[quidoooe Ajyens~) ASA MOT 1
‘ayqeonoeid se uoos se pajuswajdur
24 PINOYS YS Mo7] O} SConpas O} suOHdO yUDUNLSI] “MOT OF YSLE OY) PONPes OF sud: UNA JO WOE WaWs|du MSM ALVUsaGow Ww
pue Sujuuyjd ‘uonesnsoaut sosnbos ing (jeaoudde s_s0;e[NFos OF jOalqns) SoOURISUINDID UTELIDD UT Payes9jO1 9q ALP
“Kpodoud oq Jo onjva Oy) 0) UOHU]Al UI MINS [EHUEISGNS B ISOS P[NOM Oy “AO OF SU 2
2onpas 0} posnbaz suondo jusuyeay Jo UONLuoWadun pues BurmuRd ‘UONPEYSoAU! papElog, “USWRAN joy ajqQeuidoooeu
“Auodoid
YI JO aNTBA UvY) o10W }sO9 OF AJaXI] YIOA\ “]LONIeId JOU pue aAIsUsdxa OO} aq ABU SMO7] OF YSIA DONPod OF uasso suondo
juouyran Jo UOHRUaWalduuy pue SuluuEld “youwasas puv UOETNSeaut pojmiep salsuaxy “qUSUNeON INoYyLAS e1qeideoowUA
() suoneaydury sdurexy BAT ISR
SNOILVOITHAT THAAT MSTA
“oun
quoUINS arp Ie paywowsjduy 9q 1OU ABU YOIYM SouNsedW JONUOD YSU WLW JO SUOFNPUOD Bunsexa Joy StH sDYIOYAr payeys Apsw9/9 aq ISNUE JI JUDUISSOSSE YSU B BULSpIsuos UDYA\ (9)
“YSIY MOT SI &%]"O UY] Ssa] JO 99UDNbasUOD vB JEL YoNs PoplAlpqns aq Aewi “gy [19D 104 (sg) :s930N
TA TA TA dA 1 a1s1GaUd ATANVa 4
TA 1A fi 1 Ww auva a
VA q q Ww = Fee s ATAMVINA a
TA Ww Ww Ie =— alaissOd - 3
q Ww ATAIMIT a
(s) 1401 NIVINGS LSOWIV Vv
%eSO qu Gord
LNVOLIINDISNI %S %o0T %09 %oV0T fenuuay aeurxoaddy
is MONI? wordgaw = MOLVA 27 OMdOULSV.LYO 31 JO an EA PAHESPUT
(asewEG Jo oD aeunxosddy saneorpul WM) ALAAdOUd OL SAONANOASNOD GOOHITAINIT
ALYAMOUd OL MSTA AO THATT — XTILVW SISATWNV MSTA FALLVLITKAO
(G4aNNILNOOD) ALAAAOUd OL MSN ONISSASSV NI ASN AOA ADOTONUIAAAL AALLVLITVNO — *O XIGNAddV
4002 LNSWS9VNVW MSI SACMSAGNV1 YOS SANITAGINS SALON SDILOWed
Page 25
LINDSAY CONSULTING PTY LTD -
STRUCTURAL AND CIVIL ENGINEERS
ACN 079 744 808 ABN 61 478 386 385 GST REGISTERED
AS TRUSTEE FOR THE LINDSAY FAMILY TRUST
APPENDIX C
AUSTRALIAN GEOGUIDES
LR3 – LANDSLIDES IN SOILS
LR5 – WATER AND DRAINAGE
LR7 – LANDSLIDE RISKS
LR8 – CONSTRUCTION PRACTICES
Off. 2C/82 Parker St, Maroochydore 4558
OFFICE: (07) 54 792 118 MOBILE: 0412 313 645 FAX: (07) 54 510 118
E-MAIL: [email protected]
Page 26
AUSTRALIAN GEOGUIDE LR3 (LANDSLIDES IN SOIL)
Landslides occur on soil slopes and the consequences can include damage to property and loss of life. Soil slopes exist
in all parts of Australia and can even occur in places where rock outcrops can be seen on the surface. If you live on, or
below, a soil slope it is important to understand why a landslide might occur and what you can do to reduce the risk it
presents.
It is always worth asking the question 'why is this slope here?", because the answer often leads to an understanding of
what might happen in the future. Slopes are usually formed by weathering (breakdown) and erosion (physical
Movement) of the natural ground - the "parent material". Many factors are involved including rain, wind, chemical
change, temperature variation, plant growth, animal activity and our own human enthusiasm for development. The
general process is outlined in Figure 1.
The upper levels of the parent material progressively weather over thousands, or millions, of years, losing strength. This
can result in a surface layer which looks similar to the parent material (although its colour has probably changed) but has
the strength of a soil - this is called “residual soil. At some stage the weathered surface layer is exposed to the
elements and fragments are transported down the slope. In this context a fragment could be a single sand grain, a
boulder, or a landslide. The time scale could be anything from a few seconds to many thousands of years. The
transported fragments often collect on the lower slopes and form a new soil layer that blankets the original slope -
"colluvium". If material reaches a river or the sea it is deposited as "alluvium" or as a "marine deposit". With appropriate
changes in river and sea level this material can again find itself on the surface to commence another cycle of weathering
and erosion. In places often, but not only, near the coast, this can include sand sized fragments which form beaches and
are sometimes blown back onto the land to form dunes.
all wae
= s
Weathered parent material
(residual soil)
Fragments of parent material
transported down slope
Gare} Figure 2 Remnant
material ancient
landslide
River
or sea
Water or wind deposited soils
‘ (alluvium, marine deposits, or dunes)
Figure 4
Landslides can occur almost anywhere on a soil slope. Slides can be rotational, translational, or debris flows (see
GeoGuide LR2) and may have a number of causes.
a wR
mr ia
Landslide from parent material
or residual soil further uphill
Landslide due to increased
water pressures, or
Rise in water table, or an
increase in water content can :
be due to tree clearance, installing
soakaway drains, or a period of heavy rain ~~
Figure 2
164 Australian Geomechanics Vol 42 No 1 March 2007
Page 27
AUSTRALIAN GEOGUIDE LR3 (LANDSLIDES IN SOIL) pn or N Landslide due to poorly supported excavation, excessive fill depth, steep excavated cut face or inadequately designed shallow foundations Ancient landslide reactivated by led rainfallor major reshaping e landscape _— 3 Some of the more common causes of landslides in soil are: 1) Falls of the parent material or residual soil from above, due to natural weathering processes (Figure 2), 2) Increased moisture content and consequent softening of the soil, or a rise in the water table. These can be due to excessive tree clearance, ill-considered soak-away drainage or septic systems, or heavy rainfall (Figure 2). 3) Excavation without adequate support, increased surface load from fill placement, or inadequately designed shallow foundations (Figure 3). 4) Natural erosion at the toe of the slope due to scour by a river or the sea (Figure 3). 5) Re-activation of an ancient landslide (Figure 3), Most soil slopes appear stable, but they all achieved their present shape through a process of weathering and erosion and are often sensitive to minor changes in the factors that affect their stability. As a general rule, human activities only improve the situation if they have been designed to do so, Once this idea is understood, it is probably easy to see why the following basic rules are so important and should not be ignored without seeking site specific advice from a geotechnical practitioner: . Do not clear trees unnecessarily. . Do not cut into a slope without supporting the excavated face with an engineer designed structure, . Do not add weight to a slope by placing earth fill or constructing buildings with inadequately designed shallow foundations (Note: in certain circumstances weight is added to the toe of a slope to inhibit landslide movement, but this must be carried out in accordance with a proper engineering design). . Do not allow water from storm water drains, or from septic waste or effluent disposal systems to soak into the ground where it could trigger a landslide. More information in relation to good and poor hillside construction practice is given in GeoGuide LR8, With appropriate engineering input it is often possible to reduce the likelihood, or consequences, of a landslide and so reduce the risk to property and to life. Such measures can include the construction of properly designed storm water and sub-soil drains, surtace oe (Seoguce LRS) and aes walls ee LR6). Design should be undertaken by a More Information relevant to your particular situation may be found in other Australian GeoGuides: GeoGuide LR1 - Introduction GeoGuide LR2 - Landslides GeoGuide LR4 - Landslides in Rock GeoGuide LR5 - Water & Drainage GeoGuide LR6 - Retaining Walls GeoGuide LR7 - Landslide Risk GeoGuide LR8 = - Hillside Construction GeoGuide LR9 - Effluent & Surface Water Disposal GeoGulde LR10 - Coastal Landslides GeoGuide LR11 - Record Keeping The Australian GeoGuldes (LR series) are a set of publications Intended for properly owners; local councils; planning authorities; developers; insurers; lawyers and, in fact, anyone who lives with, or has an interest in, a natural or engineered slope, a cutling, or an excavation. They are intended to help you understand why slopes and retaining structures can be a hazard and whal can be done with appropriate professional advice and local council approval (if required) to remove, reduce, or minimise the risk they represent. The GeoGuides have been prepared by the Australian Geomechanics Sociely, a specialist technical sociely within Engineers Australia, the national peak body for all engineering disciplines in Australia, whose members are professional geotechnical engineers and engineering geologists with a particular interest in ground engineering. The GeoGuides have been funded under the Australian governments’ National Disaster Mitigation Program. Australian Geomechanics Vol 42 No 1 March 2007 165
Page 28
AUSTRALIAN GEOGUIDE LR5 (WATER & DRAINAGE)
One way of another, water usually plays a critical part in initiating a landslide (GeoGuide LR2). For this reason, it is a
key factor to be controlled on sites with more than a low landslide risk (GeoGuide LR7).
Groundwater and Groundwater Flow
The ground is permeable and water flows through it as illustrated in Figure 1. When rain falls on the ground, some of it
tuns along the surface ("surface water run-off’) and some soaks in, becoming groundwater. Groundwater seeps
downwards along any path it can find until it meets the water table: the local level below which the ground is saturated. If
it reaches the water table, groundwater either comes to a halt in what is effectively underground storage, or it continues
to flow downwards, often towards a spring where it can seep out and become surface water again, Above the water
table the ground is said to be "partially saturated", because it contains both water and, air. Suctions can develop in the
partially saturated zone which have the effect of holding the ground together and reducing the risk of a landslide.
Vegetation and trees in particular draw large quantities of water out of the ground on a daily basis from the partially
saturated zone. This lowers the water table and increases suctions, both of which reduce the likelihood of a landslide
occurring,
Figure 1 - Groundwater flow
Groundwater Flow and Landslides
The landslide risk in @ hillside can be affected by increase in soak-away drainage or the construction of retaining walls
which inhibit groundwater flow. The groundwater is likely to rise after heavy rain, but it can also rise when human
interference upsets the delicate natural balance. Activities such as felling trees and earthworks can lead to:
¢ — areduction in the beneficial suctions in the partially saturated zone above the water table.
increased static water pressures below the water table,
increased hydraulic pressures due to groundwater flow,
loss of strength, or softening, of clay rich strata,
loss of natural cementing in some strata,
transportation of soil particles,
Any of these effects, or a combination of them, can lead to landslides like those illustrated in GeoGuides LR2, LR3 and
LRA.
Limiting the Effect of Water
Site clearance and construction must be carefully considered if changes in groundwater conditions are to be limited.
GeoGuide LR8 considers good and poor development practices. Not surprisingly much of the advice relates to sensible
treatment of water and is not repeated here. Adoption of appropriate techniques should make it possible to either
maintain the current ground water table, or even cause It to drop, by limiting inflow to the ground.
If drainage measures and surface protection are relied on to keep the risk of a landslide to a tolerable level, it is important
that they are inspected routinely and maintained (GeoGuide LR11).
The following techniques may be considered to limit the destabilising effects of rising groundwater due to development
and are illustrated in Figure 2.
168 Australian Geomechanics Vol 42 No 1 March 2007
Page 29
AUSTRALIAN GEOGUIDE LRS5 (WATER & DRAINAGE) Figure 2 - Techniques used to control groundwater flow Surface water drains (dish drains, or table drains) - are often used to prevent scour and limit inflow to a slope. Other than in rock, they are relatively ineffective unless they have an impermeable lining. You should clear them regularly, and as required, and not less than once a year, If you live in an area with seasonal rainfall, it is best to do this near the end of the dry season. If you notice that soil or rock debris is falling from the slope above, determine the source and take appropriate action. This may mean you have to seek advice from a geotechnical practitioner. Surface protection - is sometimes used in addition to surface water drainage to prevent scour and minimise water inflow to a slope. You should inspect concrete, shoterete or stone pitching for cracking and other signs of deterioration at least once a year. Make sure that weepholes are free of obstructions and able to drain. If the protection is deteriorating, you should seek advice from a geotechnical practitioner. Sub-soil drains - are often constructed behind retaining walls and on hillsides to intercept groundwater. Their function is to remove water from the ground through an appropriate outlet. It is important that subsoil drains are designed to complement other measures being used. They should be laid in a sand, or gravel, bed and protected with a graded stone or geotextile filter to reduce the chance of clogging. Sub-soil drains should always be laid to a fall of at least 1 vertical on 100 horizontal. Ideally the high end should be brought to the surface, so it can be flushed with water from time to time as part of routine maintenance procedures, Deep, underground drains - are usually only used in extreme circumstances, where the landslide risk is assessed as not being tolerable and other stabilisation measures are considered to be impractical. They work by permanently lowering the water table in a slope. They are not often used in domestic scale developments, but if you have any on your site be aware that professional maintenance is essential. If they are not maintained and stop working, the water table will rise and a landslide may even occur during normal weather conditions. Both an increase or a reduction in the normal flow from deep drains could indicate a problem if it appears to be unrelated to recent rainfall. If changes of this sort are observed, you should have the drains and your site checked by a geotechnical practitioner. Documentation - design drawings and specifications for geotechnical measures intended to minimise landslide risk can be of great assistance to a geotechnical specialist, or structural engineer, called in to inspect and report on them. Copies of available documentation should be retained and passed to the new owner when the property is sold (GeoGuide LR11). You should also request details of an appropriate maintenance program for drainage works from the designer and keep that information with other relevant documentation and maintenance records. More information relevant to your particular situation may be found In other Australian GeoGuldes: * GeoGuide LR1 - Introduction « GeoGuide LR7 - Landslide Risk * GeoGuide LR2 - Landslides « GeoGulde LR8 - Hillside Construction © GeoGuideLR3 - Landslides in Soll « GeoGuide LR9 - Effluent & Surface Water Disposal * GeoGuide LR4 - Landslides in Rock * GeoGuide LR10 - Coastal Landslides * GeoGuide LR6 - Retaining Walls * GeoGuide LR11 - Record Keeping The Australian GeoGuides (LR series) are a set of publications intended for property owners; local councils; planning authorities; developers; insurers; lawyers and, in fact, anyone who lives with, or has an interest in, a natural or engineered slope, a culling, or an excavation. They are intended lo help you understand why slopes and retaining structures can be @ hazard and what can be done with appropriate professional advice and local council approval (if required) to remove, reduce, or minimise the risk they represent. The GeoGuides have been prepared by the Australian Geomechanics Sociely. a specialist technical sociely within Engineers Australia, the national peak body for all engineering disciplines in Australia, whose members are professional geotechnical engineers and engineering geologists with a particular interest in ground engineering. The GeoGuides have been funded under the Australian governments’ National Disaster Mitigation Program. Australian Geomechanics Vol 42 No 1 March 2007 169
Page 30
AUSTRALIAN GEQGUIDE LR7 (LANDSLIDE RISK) Concept of Risk Risk is a familiar term, but what does it really mean? It can be defined as “a measure of the probability and severity of an adverse effect to health, property, or the environment.” This definition may seem a_ bit complicated. In relation to landslides, geotechnical practitioners (GeoGuide LR1) are required to assess risk in terms of the likelihood that a particular landslide will occur and the possible consequences. This is called landslide risk assessment. The consequences of a landslide are many and varied, but our concerns normally focus on loss of, or damage to, property and loss of life. Landslide Risk Assessment Some local councils in Australia are aware of the potential for landslides within their jurisdiction and have fesponded by designating specific “landslide hazard zones" Development in these areas is often covered by special regulations. If you are contemplating building, or buying an existing house, particularly in a hilly area, or near cliffs, go first for information to your local council. Landslide risk assessment must be undertaken by geotechnical practitioner. It may involve visuel inspection, geological mapping, — geotechnical investigation and monitoring to identify: * potential landslides (there may be more than ‘one that could impact on your site) the likelihood that they will occur the damage that could result the cost of disruption and repairs and the extent to which lives could be lost. Risk assessment is a predictive exercise, but since the ground and the processes involved are complex, prediction tends to lack precision. If you commission a landslide risk assessment for a particular site you should expect to receive a report prepared in accordance with current professional guidelines and in a form that is acceptable to your local council, or planning authority. Risk to Property Table 1 indicates the terms used to describe risk to property, Each risk level depends on an assessment of how likely a landslide is to occur and its consequences in dollar terms. "Likelihood" is the chance of it happening in any one year, as indicated in Table 2. "Consequences" are related to the cost of repairs and temporary loss of use if a landslide occurs. These two factors are combined by the geotechnical practitioner to determine the Qualitative Risk, TABLE 2: LIKELIHOOD Annual Almost Certain 4:10 1: 4:4,000 Rare 4:100,000, credible 71,000,000 The terms "unacceptable", “may be tolerated", etc, in Table 1 indicate how most people react fo an assessed risk level. However, some people will always be more prepared, or better able, to tolerate a higher risk level than others. Some local councils and planning authorities stipulate a maximum tolerable level of risk to property for developments within their jurisdictions, In these situations the risk must be assessed by 2 geotechnical practitioner. If stabilisation works are needed to meet the stipulated requirements these will normally have to be carried out as part of the development, or consent will be withheld, TABLE 1; RISK TO PROPERTY Significance - Geotechnical engineering requirements Qualitative Risk Very high | VH | Unacceptable without treatment. Extensive detailed investigation and research, planning and implementation of treatment options essential to reduce risk to Low. May be too expensive and not practical. Work likely to cost more than the value of the property. Unacceptable without treatment. Detailed investigation, planning and implementation of treatment options required to reduce risk to acceptable level. Work would cost a substantial sum in relation to the value of the property. May be tolerated in certain circumstances (subject to regulator's approval) but requires investigation, planning and implementation of treatment options to reduce the risk to Low. Treatment options to reduce to Low risk should be implemented as soon as possible. Usually acceptable to regulators. Where treatment has been needed to reduce the risk to this level, ongoing maintenance is required. High H Moderate | M Very Low | VL | Acceptable. Manage by normal slope maintenance procedures. 172 Australian Geomechanics Vol 42 No 4 March 2007
Page 31
AUSTRALIAN GEOGUIDE LR7 (LANDSLIDE RISK) Risk to Life Most of us have some difficulty grappling with the concept of risk and deciding whether, or not, we are prepared to accept it. However, without doing any sort of analysis, or commissioning a report from an “expert”, we all take risks every day. One of them is the risk of being killed in an accident. This is worth thinking about, because it tells us a lot about ourselves and can help to put an assessed risk into a meaningful context. By identifying activities that we either are, or are not, prepared to engage in we can get some indication of the maximum level of risk that we are prepared to take. This knowledge can help us to decide whether we really are able to accept a particular risk, or to tolerate a particular likelihood of loss, or damage, to our property (Table 2), In Table 3, data from NSW for the years 1998 to 2002, and other sources, is presented. A risk of 1.in 100,000 means that, in any one year, 1 person is killed for every 100,000 people undertaking that particular activity. The NSW data assumes that the whole population undertakes the activity, That is, we are all at risk of being killed in a fire, or of choking on our food, but it is reasonable to assume that only people who go deep sea fishing run a risk of being killed while doing it. It can be seen that the risks of dying as a result of falling, using a motor vehicle, or engaging in water- related activities (including bathing) are all greater than 1:100,000 and yet few people actively avoid situations where these risks are present. Some people are averse to flying and yet it represents a lower risk than choking to death on food. Importantly, the data also indicate that, even when the risk of dying as a consequence of a particular event is very small, it could still happen to any one of us any day. If this were not so, no one would ever be struck by lightning. Most local councils and planning authorities that stipulate a tolerable risk to property also stipulate a tolerable risk to life. The AGS Practice Note Guideline recommends that 1:100,000 is tolerable in newly developed areas, where works can be carried out as part of the development to limit risk. The tolerable level is raised to 1:10,000 in established areas, where specific landslide hazards may have existed for many years. The distinction is deliberate and intended to prevent the concept of landslide risk management, for its own sake, becoming an unreasonable financial burden on existing communities. Acceptable risk is usually taken to be one tenth of the tolerable risk (1:1,000,000 for new developments and 1:100,000 for established areas) and efforts should be made to attain these where it is practicable and financially realistic to do so. TABLE 3: RISK TO LIFE Risk (deaths per Activity/Event Leading to participant per Death year) (NSW data unless noted) 1:1,000 Deep sea fishing (UK) Te 0) Motor cycfing, horse riding , . ultra-light flying (Canada) 4:23,000 Motor vehicle use 1:30,000 Fall 1:70,000 Drowning 1:180,000 Fire/burn 1:660,000 Choking on food 1:1,000,000 Scheduled airlines (Canada) 1:2,300,000 Train travel 1:32,000,000 Lightning strike More information relevant to your particular situation may be found in other AUSTRALIAN GEOGUIDES: GeoGuide LR1 - Introduction GeoGuide LR2 - Landslides GeoGuide LR3_ - Landslides in Soil GeoGuide LR4 - Landslides in Rock GeoGuide LR5 - Water & Drainage wees GeoGuide LR6 - Retaining Walls GeoGuide LR8 - Hillside Construction GeoGuide LRO = - Effluent & Surface Water Disposal GeoGulde LR10 - Coastal Landslides GeoGuide LR11 - Record Keeping The Australian GeoGuides (LR series) are a set of publications intended for properly owners; local councils, planning authorilies; developers; insurers; lawyers and, in fact, anyone who lives with, or has an interest in, a nalural or engineered slope, a cutting, or an excavation They are intended to help you understand why slopes and retaining structures can be a hazard and what car be done with appropriate professional advice and local council approval (if required) to remove, reduce, or minimise the risk they represent. The GeoGuldes have been prepared by the Australian Geomechanics Society. a specialist technical sociely wilhin Engineers Australia, the National peak body for all engineering disciplines in Australia, whose members are professional geotechnical engineers and engineering geologists with a particular interest in ground engineering National Disaster Mitigation Program. The GeoGuides have been funded under the Australian governments’ Australian Geomechanics Vol 42 No 1 March 2007 173
Page 32
AUSTRALIAN GEOGUIDE LR8 (CONSTRUCTION PRACTICE) Sensible development practices are required when building on hillsides, particularly if the hillside has more than a low risk of instability (GeoGuide LR7). Only building techniques intended to maintain, or reduce, the overall level of landslide risk should be considered. Examples of good hillside construction practice are illustrated below. EXAMPLES OF GOOD HILLSIDE CONSTRUCTION PRACTICE we Vegetation retained ‘Surface water interception drainage \ of Walertight, adequately siled and founded roof water storage \ tanks (with due regard for impact of potential leakage) —____—— \g Flexible structure Roof water piped off site or stored ———__—— On-site detention tanks, walertight and adequately founded. Potential leakage managed by sub-soil drains "Pier footings into rock ~~ Subsoil drainage may be fequired in slope \ ~ Cutting and filling minimised in development \ Sewage effiuent pumped out or connected to sewer. Tanks adequately founded and watertight. Potential leakage managed by sub-soll drains ~\___ Engineered retaining walls wth both surface and fs subsurface drainage (constructed before dwelling) ©) AGS (?007) Ss ‘Son also AGS (2000) Appanaix J WHY ARE THESE PRACTICES GOOD? Roadways and parking areas - are paved and incorporate kerbs which prevent water discharging straight into the hillside (GeoGuide LR5). Cuttings - are supported by retaining walls (GeoGuide LR6). Retaining walls - are engineer designed to withstand the lateral earth pressures and surcharges expected, and include drains to prevent water pressures developing in the backfill. Where the ground slopes steeply down towards the high side of a retaining wall, the disturbing force (see GeoGuide LR8) can be two or more times that in level ground. Retaining walls must be designed taking these forces into account. Sewage - whether treated or not is either taken away in pipes or contained in properly founded tanks so it cannot soak into the ground. Surface water - from roofs and other hard surfaces is piped away to a suitable discharge point rather than being allowed to infiltrate into the ground. Preferably, the discharge point will be in a natural creek where ground water exits, rather than enters, the ground. Shallow, lined, drains on the surface can fulfil the same purpose (GeoGuide LRS). Surface loads - are minimised. No fill embankments have been built, The house is a lightweight structure. Foundation loads have been taken down below the level at which a landslide is likely to occur and, preferably, to rock. This sort of construction is probably not applicable to soil slopes (GeoGuide LR3). If you are uncertain whether your site has rock near the surface, or is essentially a soil slope, you should engage a geotechnical practitioner to find out. Flexible structures - have been used because they can tolerate a certain amount of movement with minimal signs of distress and maintain their functionality. Vegetation clearance - on soil slopes has been kept to a reasonable minimum. Trees, and to a lesser extent smaller vegetation, take large quantities of water out of the ground every day. This lowers the ground water table, which in turn helps to maintain the stability of the slope. Large scale clearing can result in a rise in water table with a consequent increase in the likelihood of a landslide (GeoGuide LR5). An exception may have to be made to this rule on steep rock slopes where trees have little effect on the water table, but their roots pose a landslide hazard by dislodging boulders. Possible effects of ignoring good construction practices are illustrated on page 2. Unfortunately, these poor construction practices are not as unusual as you might think and are often chosen because, on the face of it, they will save the developer, or owner, money. You should not lose sight of the fact that the cost and anguish associated with any one of the disasters illustrated, is likely to more than wipe out any apparent savings at the outset. ADOPT GOOD PRACTICE ON HILLSIDE SITES 174 Australian Geomechanics Vol 42 No 1 March 2007
Page 33
AUSTRALIAN GEOGUIDE LR8 (CONSTRUCTION PRACTICE) EXAMPLES OF POOR HILLSIDE CONSTRUCTION PRACTICE Unslabilised rock topples and travels downslope Vegetation removed Steep unsupported cut faits \ Discharges of roofwater soak away rather than \ conducted offsite or to secure storage for re-tise Structure unable to (olerate settlement and cracks Poorly compacted fil soties S unevenly and cracks poo! fy Inadequate walling unable i to support fill i — = Ponded water enters slope and activates landslide = ~ Possible travel downslope which impacts other development downhill See eo AGS (2000) Append J WHY ARE THESE PRACTICES POOR? Roadways and parking areas - are unsurfaced and lack proper table drains (gutters) causing surface water to pond and ‘soak into the ground. Cut and fill - has been used to balance earthworks quantities and level the site leaving unstable cut faces and added large surface loads to the ground. Failure to compact the fill properly has led to settlement, which will probably continue for several years after completion. The house and pool have been built on the fill and have settled with it and cracked. Leakage from the cracked pool and the applied surface loads from the fill have combined to cause landslides. Retaining walls - have been avoided, to minimise cost, and hand placed rock walls used instead. Without applying engineering design principles, the walls have failed to provide the required support to the ground and have failed, creating a very dangerous situation. A heavy, rigid, house - has been built on shallow, conventional, footings. Not only has the brickwork cracked because of the resulting ground movements, but it has also become involved in a man-made landslide. Soak-away drainage - has been used for sewage and surface water run-off from roofs and pavements. This water soaks into the ground and raises the water table (GeoGuide LR5). Subsoil drains that run along the contours should be avoided for the same reason. If felt necessary, subsoil drains should run steeply downhill in a chevron, or herring bone, pattern. This may conflict with the requirements for effluent and surface water disposal (GeoGuide LR9) and if so, you will need to seek professional advice. Rock debris - from landslides higher up on the slope seems likely to pass through the site. Such locations are often Teferred to by geotechnical practitioners as "debris flow paths". Rock is normally even denser than ordinary fill, so even quite modest boulders are likely to weigh many tonnes and do a lot of damage once they start to roll. Boulders have been known to travel hundreds of metres downhill leaving behind a trail of destruction. Vegetation - has been completely cleared, leading to a possible rise in the water table and increased landslide risk (GeoGuide LRS). DON'T CUT CORNERS ON HILLSIDE SITES - OBTAIN ADVICE FROM A GEOTECHNICAL PRACTITIONER More information relevant to your particular situation may be found in other Australian GeoGuides: * GeoGuideLR1 - Introduction * GeoGuide LR6 - Retaining Walls ¢ GeoGuideLR2 - Landslides « GeoGuide LR7 - Landslide Risk * GeoGuide LR3 - Landslides in Soil * GeoGuide LR - Effluent & Surface Water Disposal * GeoGuide LR4 - Landslides in Rock GeoGuide LR10 - Coastal Landslides + _GeoGuide LR5 _- Water & Drainage * —GeoGuide LR11 - Record Keeping The Australian GeoGuides (LR series) are a set of publications intentled for property owners; local councils; planning authorities; developers; insurers; lawyers and, in facl, anyone who lives with, or has an interest in, a nalural or engineered slope, @ cutting, or an excavalion. They are intended (o help you understand why slopes and retaining structures can be a hazard and what can be done with appropriate professional advice and local council approval (if required) to remove, reduce, or minimise the risk they represent. The GeoGuides have been prepared by the Australian Geomechanics Sociely, a specialist technical society within Engineers Australia, the national peak body for all engineering disciplines in Australia, whose members are professional geolechnical engineers and engineering geologists with a particular interest in ground engineering, The GeoGuides have been funded under the Australian governments’ National Disaster Mitigation Program. Australian Geomechanics Vol 42 No 1 March 2007 175
Page 34
APPENDIX G - SOME GUIDELINES FOR HILLSIDE CONSTRUCTION Pipes. ‘Where structural distress is evident see advice. If seepage observed determine cases or seek advice on consequences. GOOD ENGINEERING PRACTICE POOR ENGINEERING PRACTICE ADVICE GEOTECHNICAL Obtain advice from a qualified, experienced geotechmical practitioner at early | Prepare detailed plan and start site works before ASSESSMENT stage of planning and before site works. geotechnical advice. PLANNING = _ SITE PLANNING Having obtained geotechnical advice. plan the development with the risk | Plan development without regard for the Risk. arising from the identified hazards and consequences in muind. DESIGN AND CONSTRUCTION ¥ ‘Use flemtble structures which incorporate properly desiened brickwork, timber | Floor plans which require extensive cutting and HOUSE DESIGN | 0! tee! Stames, timber or pane! clactime, filling. Consider use of split levels. Movement intolerant structures. Use decks for recreational areas where appropriate. SITE CLEARING Retain natural vegetanon wherever practicable. Indiscrmmnately clear the site. ACCESS & Satisfy requirements delow for cuts, fills, retaining walls and drainage. Excavate and fill for site access before DRIVEWAYS Council spectfications for grades may need to be modified. geotechnical advice Driveways and parking areas may need to be fully supported on piers. EARTHWORKS Retain natwal contours wherever possible. Tndiscrmmatory bulk earthworks. Minimise depeh Large scale cuts and benching. Ours Support with engineered retaining walls or batter to appropriate slope. Unsupported cuts Provide drainage measures and erosion control Ignore drainage requirements ‘Minute height ‘Loose or poorly compacted fill, which if it falls, Strip vegetation and topsoil and key into natural slopes prior to filling. way flow a considerable distance including Use clean fill materials and compact to engineering standards. onto property below. Fars Batter to appropriate slope or suppart with engineered retaining wall Block natural drainage lines. Provide surtace dramage and appropriate subsurface drainage. Fill over existing vegetation and topsail. Include stumps, trees, vegetation, topsoil boulders, building mibble etc in fill Rock Ourcrors | Remove or stabilise boulders which may have unacceptable risk. Distrd or undercut detachad Blocks or & Bowers Support rock faces where necessary. boulders. Engineer design to resist applied soi! and water forces. Construct a structurally inadequate wall such as RETADING Found on rock where practicable sandstone flagging, brick or umreinforced WALLS Provide subsurface drainage within wall backfill and surface drainage on slope | blockwork above Lack of subsurface drains and weepholes. Construct wall as soon as possible after cut fill operation. Found within rock where pracacable Found on topsoil, loose 11 detached boulders FOOTINGS Use rows of piers or strip footings oriented up and down slope. orundercut cliffs. Desizm for lateral creep pressures if necessary. Backfill footing excavations to exclude ingress of surface water. Engineer designed Support on piers to rock where practicable. SWIMMING POOLS | Provide with under-drainage and gravity drain outlet where Design for high soil pressures which may develop on uphill side whilst there muay be lirtle or no lateral support on downhill side DRAINAGE Provide at tops of cut and fill slopes. Discharge at top of fills and cuts. Discharge to street drainage or natural water courses Allow water to pond on bench areas. SURFACE Provide general fails to prevent blockage by siltation and incorporate silt traps Line to minimise mnfilzation and make flexible where possible Special structures to dissipate energy at chanzes of slope and/or direction. Provide filter around subsurface drain Discharge roof nmoé into absorption trenches. Sunsunrace | Provide drain behind retaining walls. Use flexible pipelines with access for maintenance. Prevent inflow of surface water. Semck Usually requires pump-put or main: sewer systems; absorption trenches may | Discharge sullage directly onto and into slopes. Surtage be possible im some areas if risk is acceptable. Use absorption menches without consideration Storage tanks should be water-tight and adequately founded. of landslide nck. EROSION Control erosion as this may lead to instability. Failure to observe earthworks and dramage CONTROL & Revegetate cleared area. recommendations when landscaping. LANDSCAPING DRAWINGS AND SITE VISITS DURING CONSTRUCTION DRAWINGS Building Applicanon drawings should be viewed by geotechnical consulmnt STE VISITS Site Visits by consultant may be appropriate durmz construction’ INSPECTION AND MAINTENANCE BY OWNER OWNER’S Clean dramage systems; repair broken joints in drams and aks im supply RESPONSIBILITY
Page 35
LINDSAY CONSULTING PTY LTD -
STRUCTURAL AND CIVIL ENGINEERS
ACN 079 744 808 ABN 61 478 386 385 GST REGISTERED
AS TRUSTEE FOR THE LINDSAY FAMILY TRUST
APPENDIX D – IMPORTANT INFORMATION
REGARDING GEOTECHNICAL ENGINEERING
REPORTS
Off. 2C/82 Parker St, Maroochydore 4558
OFFICE: (07) 54 792 118 MOBILE: 0412 313 645 FAX: (07) 54 510 118
E-MAIL: [email protected]
Page 36
Page 37
the report's recommendations if that engineer does not perform construction observation. A Geotechnical Engineering Report Is Subject to Misinterpretation Other design team members’ misinterpretation of geotechnical engineering reports has resulted in costly problems. Lower that risk by having your geotechnical engineer confer with appropriate members of the design team after submitting the report. Also retain your geotechnical engineer to review pertinent elements of the design team’s plans and specifications. Contractors can also misinterpret a geotechnical engineering report. Reduce that risk by having your geotechnical engineer participate in prebid and preconstruction conferences, and by providing construction observation. Do Not Redraw the Engineer’s Logs Geotechnical engineers prepare final boring and testing logs based upon their interpretation of field logs and laboratory data. To prevent errors or omissions, the logs included in a geotechnical engineering report should never be redrawn for inclusion in architectural or other design drawings. Only photographic or electronic reproduction is acceptable, but recognise that separating logs from the report can elevate risk. Give Contractors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give contractors the complete geotechnical engineering report, but preface it with a clearly written letter of transmittal. In that letter, advise contractors that the report was not prepared for purposes of bid development and that the report’s accuracy is limited; encourage them to confer with the geotechnical engineer who prepared the report (a modest fee may be required) and/or to conduct additional study to obtain the specific types of information they need or prefer. A prebid conference can also be valuable. Be sure contractors have sufficient time to perform additional study. Only ASF then might you be in a position to give contractors the best information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Read Responsibility Provisions Closely Some clients, design professionals, and contractors do not recognise that geotechnical engineering is far less exact than other engineering disciplines. This lack of understanding has created unrealistic expectations that have led to disappointments, claims, and disputes. To help reduce such risks, geotechnical engineers commonly include a variety of explanatory provisions in their reports. Sometimes labelled “limitations”, many of these provisions indicate where geotechnical engineers responsibilities begin and end, to help others recognise their own responsibilities and risks. Read these provisions closely. Ask questions. Your geotechnical engineer should respond fully and frankly. Geoenvironmental Concerns Are Not Covered The equipment, techniques, and personnel used to perform a geoenvironmental study differ significantly from those used to perform a geotechnical study. For that reason, a geotechnical engineering report does not usually relate any geoenvironmental findings, conclusions, or recommendations; ¢.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated environmental problems have led to numerous project failures. If you have not yet obtained your own geocnvironmental information, ask your geotechnical consultant for risk management guidance. Do not rely on an environmental report prepared for someone else. Rely on Your Geotechnical Engineer for Additional Assistance Membership in ASFE exposes geotechnical engineers to a wide array of risk management techniques that can be of genuine benefit for everyone involved with a construction project. Confer with your ASFE member geotechnical engineer for more information. PROFESSIONAL FIRMS PRACTICING IN THE GEOSCIENCES 8811 Colesville Road Suite G10 Silver Spring, MD 20910 Telephone: 301-565-2733 Facsimile: 301-589-2017 email: [email protected] www.asle.org Copyright 1998 by ASFE, Inc. Unless ASFE grants written permission to do so, duplication of this document by any means whatsoever is expressly prohibited. Re-use of the wording in this document, in whole or in part, also is expressly prohibited, and may be done only with the express permission of ASFE or for purposes of review of scholarly research. IIGER06983.5M Page 2 of 2 GAP - Form No. 3 RL2
Page 38
APPENDIX E —- LANDSLIP HAZARD FREQUENCY ANALYSIS
Page 39
LINDSAY CONSULTING PTY LTD
Project 9 MYALL STREET, GYMPIE Project Number 231154
FACTORY POOLS
Client
LANDSLIDE FREQUENCY ANALYSIS
A NATURAL SHALLOW LANDSLIDES
FEATURE FACTOR
SLOPE ANGLE 0.500
SLOPE SHAPE 0.900
SITE GEOLOGY 1.000
MATERIAL STRENGTH 4.000
CONCENTRATION OF SURFACE WATER 0.800
EVIDENCE OF GROUNDWATER 0.700
EVIDENCE OF INSTABILITY 0.500
CALCULATED RELATIVE FREQUENCY 0.504 LOW
APPROXIMATE ANNUAL SITE PROBABLITY FOR FEATURE 2.02E-03
B ROCKFALL
FEATURE FACTOR
SLOPE OF ROCK FACE 0.000
ORIENTATION OF DEFECT SYSTEM 0.000
EVIDENCE OF INSTABILITY 0.000
CALCULATED RELATIVE FREQUENCY 0.000 N/A
APPROXIMATE ANNUAL SITE PROBABLITY FOR FEATURE 0.00E+00
C BOULDERS
FEATURE FACTOR
BOULDER SIZE 0.000
BOULDER SHAPE 0.000
SLOPE ANGLE 0.000
SLOPE SURFACE 0.000
EVIDENCE OF INSTABILITY 0.000
CALCULATED RELATIVE FREQUENCY 0.000 N/A
APPROXIMATE ANNUAL SITE PROBABLITY FOR FEATURE 0.00E+00
D FILL BATTERS
FEATURE FACTOR
FILL HEIGHT 0.200
SITE GEOLOGY 1.000
BATTER SLOPE ANGLE 0.500
NATURAL SURFACE SLOPE 0.200
EVIDENCE OF INSTABILITY 0.500
CALCULATED RELATIVE FREQUENCY 0.010 VERY LOW
APPROXIMATE ANNUAL SITE PROBABLITY FOR FEATURE 4.00E-05
E CUT BATTERS
FEATURE FACTOR
CUT HEIGHT 0.500
SLOPE OF CUT FACE 0.500
MATERIAL IN CUTTING 2.000
NATURAL SURFACE SLOPE ABOVE CUT 0.200
CUT SLOPE SUPPORT 0.500
DISTANCE OF TOE OF CUT TO STRUCTURE 2.000
EVIDENCE OF INSTABILITY 0.500
CALCULATED RELATIVE FREQUENCY 0.050 VERY LOW
APPROXIMATE ANNUAL SITE PROBABLITY FOR FEATURE 2.00E-04
Basic Frequency Adopted for Site 0.004