Appendix B - Geotechnical Investigation Report

REPORT EXPLANATION NOTES
INTRODUCTION
These notes have been provided to amplify the geotechnical report          Cohesive soils are classified on the basis of strength (consistency)
in regard to classification methods, field procedures and certain          either by use of a hand penetrometer, vane shear, laboratory testing
matters relating to the Comments and Recommendations section.              and/or tactile engineering examination. The strength terms are
Not all notes are necessarily relevant to all reports.                     defined as follows.

The ground is a product of continuing natural and man-made                                       Unconfined               Indicative Undrained
processes and therefore exhibits a variety of characteristics and                                Compressive              Shear Strength (kPa)
properties which vary from place to place and can change with time.         Classification       Strength (kPa)
Geotechnical engineering involves gathering and assimilating limited
facts about these characteristics and properties in order to                Very Soft (VS)        25                      12
understand or predict the behaviour of the ground on a particular           Soft (S)             > 25 and  50            > 12 and  25
site under certain conditions. This report may contain such facts           Firm (F)             > 50 and  100           > 25 and  50
obtained by inspection, excavation, probing, sampling, testing or           Stiff (St)           > 100 and  200          > 50 and  100
other means of investigation. If so, they are directly relevant only to
the ground at the place where and time when the investigation was           Very Stiff (VSt)     > 200 and  400          > 100 and  200
carried out.                                                                Hard (Hd)            > 400                    > 200
                                                                            Friable (Fr)         Strength not attainable – soil crumbles

DESCRIPTION AND CLASSIFICATION METHODS                                     Rock types are classified by their geological names, together with
The methods of description and classification of soils and rocks used      descriptive terms regarding weathering, strength, defects, etc.
in this report are based on Australian Standard 1726:2017                  Where relevant, further information regarding rock classification is
‘Geotechnical Site Investigations’. In general, descriptions cover the     given in the text of the report. In the Sydney Basin, ‘shale’ is used to
following properties – soil or rock type, colour, structure, strength or   describe fissile mudstone, with a weakness parallel to bedding. Rocks
density, and inclusions. Identification and classification of soil and     with alternating inter-laminations of different grain size
rock involves judgement and the Company infers accuracy only to            (eg. siltstone/claystone and siltstone/fine grained sandstone) is
the extent that is common in current geotechnical practice.                referred to as ‘laminite’.
Soil types are described according to the predominating particle size
                                                                           SAMPLING
and behaviour as set out in the attached soil classification table
qualified by the grading of other particles present (eg. sandy clay) as    Sampling is carried out during drilling or from other excavations to
set out below:                                                             allow engineering examination (and laboratory testing where
                                                                           required) of the soil or rock.
 Soil Classification             Particle Size
                                                                           Disturbed samples taken during drilling provide information on
 Clay                            < 0.002mm                                 plasticity, grain size, colour, moisture content, minor constituents
 Silt                            0.002 to 0.075mm                          and, depending upon the degree of disturbance, some information
 Sand                            0.075 to 2.36mm                           on strength and structure. Bulk samples are similar but of greater
 Gravel                          2.36 to 63mm                              volume required for some test procedures.
 Cobbles                         63 to 200mm                               Undisturbed samples are taken by pushing a thin-walled sample tube,
 Boulders                        > 200mm                                   usually 50mm diameter (known as a U50), into the soil and
                                                                           withdrawing it with a sample of the soil contained in a relatively
Non-cohesive soils are classified on the basis of relative density,        undisturbed state. Such samples yield information on structure and
generally from the results of Standard Penetration Test (SPT) as           strength, and are necessary for laboratory determination of shrink-
below:                                                                     swell behaviour, strength and compressibility. Undisturbed sampling
                                                                           is generally effective only in cohesive soils.
                                 SPT ‘N’ Value                             Details of the type and method of sampling used are given on the
 Relative Density                (blows/300mm)                             attached logs.
 Very loose (VL)                 <4
 Loose (L)                       4 to 10
 Medium dense (MD)               10 to 30
 Dense (D)                       30 to 50
 Very Dense (VD)                 > 50




February 2019                                                        1