Approved Plan - EXE21-0015

Mr Dean Frith                                                                                           21182-001-Rev0
                                                                                                           28 May 2021

4.3       Earthworks
No further cutting (with the exception for remediation works) or filling should be carried out on site for the shed
area unless reviewed and approved by Tectonic. If further earthworks are planned Tectonic must review
potential impacts on slope stability.

All vegetation, tree stumps and large roots must be ‘grubbed out’ scross proposed building areas. Any
organic rich topsoil (although not anticipated) should then be stripped and set aside. Organic topsoils and
garden soils must not be re-used as fill; however, they may be retained on site for later use across
landscaping areas, if required. Ground surfaces should be graded to shed surface water runoff away from
construction areas.

Permanent batter slopes should be constructed as follows:

      ▪    Fill embankments to a maximum grade of 1V:2.5H
      ▪    Cut batters in natural soil consisting of stiff (or stiffer) clay to a maximum grade of 1V:2H
      ▪    Cut batters in weathered rock to a maximum grade of 1V:1H

Steeper batters should be re-profiled. Where spatial restrictions exist, batters should be retained by
engineer designed retaining walls (ref. Section 4.4 below).

Although trafficability should generally be good in ‘dry’ conditions, the soils could be subject to strength loss
from repetitive vehicle loading (particularly from rubber tyred plant) or if they become wet. Due to the
potential for poor trafficability during and after wet periods, placement of a minimum 150 mm thick granular
working platform may be required, particularly along access ways.

4.4       Retaining Structures
Retaining structures must be founded as described in Section 4.5 below. Retaining structures greater than
1 m high will require engineer design and certification of construction. Retaining structures should be
engineer designed in accordance with AS4678-2002 Earth-retaining structures.

We suggest the following parameters may be adopted for retaining wall design.
 Table 3: Retaining Wall Design Parameters
                                                                  Lateral earth pressure coefficients
                             Unit       Friction
 Retained material         weight        angle
                                                             Ka                      Ko
                           (kN/m3)     (Degrees)                                                         Kp
                                                      (Cantilever wall)      (Non-yielding wall)


 Firm to Stiff Clay           19           25               0.40                    0.57                2.46


 Weathered Rock               21           36               0.26                    0.41                3.85



These parameters do not include allowance for surcharge above the wall, or additional loads imposed by
sloping ground.

Subsurface drainage must be installed behind any retaining walls (e.g. slotted ‘aggi’ pipe wrapped in filter
‘sock’ placed in gravel backfill). Depending on matters such as the extent of drainage installed and site-
specific groundwater conditions, the designer must make an assessment of hydrostatic pressure to be
accounted for in the design of the retaining structure.

4.5       Footing Design
Footings for the proposed shed and any ancillary structures (e.g. tanks or retaining walls) should penetrate
through any fill, and residual soils, to found a minimum of 0.3 m into weathered rock. Footings so founded
may be designed using an allowable bearing pressure of 400 kPa. Footings located in cut areas may be
founded directly on weathered rock, and may therefore comprise conventional slab edge/internal beams,




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