Appendix B- Geotechnical Investigation

                                                              -2-

TEST LOCATIONS                                                      the drilling. The depth of refusal of the different bit
Test locations (e.g. boreholes, CPT’s, test pits etc.)              types can provide information as to the strength of the
were based on available access at the time of testing               material encountered. Generally two different bit types
(access may need to be provided “by others”). Test                  are used. The 'V' bit is a V shaped steel bit and the
locations may have been shifted if access was not                   'TC' bit is a tungsten carbide tipped screw type bit.
suitable.                                                           Wash Boring - The borehole is usually advanced by a
Unless noted otherwise, accuracy of test locations are              rotary bit with water or fluid pumped down the hollow
to the accuracy of hand held GPS equipment.                         drill rods and returned up in the space between the
INVESTIGATION METHODS                                               rods and the soil or casing, carrying the drill cuttings.
The following is a brief summary of investigation                   Only major changes in stratification can be determined
methods currently adopted by the Company and some                   from the cuttings, together with some information from
comments on their use and application.                              "feel"   and     rate    of    penetration.   More      accurate

Test Pits - These are normally excavated with a                     information on soil strata is gained by regular testing

backhoe or a tracked excavator, allowing close                      and sampling using the Standard Penetration Test

examination of the insitu soils if it is safe to descend            (SPT) and undisturbed thin walled tube samples (U50).

into the pit. The depth of penetration is limited to about          Mud Stabilized Drilling - Either Wash Boring or
3m for a backhoe and up to 6m for an excavator.                     Continuous Core Drilling can use drilling mud as a
Limitations of test pits are the problems associated                circulating fluid to stabilize the borehole.         The term
with disturbance and difficulty of reinstatement and the            "mud" encompasses a range of products ranging from
consequent effects on close-by structures. Care must                bentonite to polymers such as Revert or Biogel. The
be taken if construction is to be carried out near test pit         mud      tends   to     mask     the   cuttings   and    reliable
locations to either properly recompact the backfill                 identification is only possible from regular intact
during construction or to design and construct the                  sampling (eg. from SPT and U50 samples) or from
structure so as not to be adversely affected by poorly              rock coring, etc.
compacted backfill at the test pit location.                        Continuous Core Drilling - A continuous core sample
Hand Auger Drilling - A borehole of 50 to 100mm                     is obtained using a diamond or tungsten carbide
diameter     is    advanced        by       manually   operated     tipped core barrel.           Provided full core recovery is
equipment. Refusal of the augers can occur on a                     achieved (which is not always possible in very weak
variety of materials such as hard clay, gravel or rock              rocks and granular soils), this technique provides a
fragments and does not necessarily indicate rock level.             very reliable method of investigation. In rocks, NMLC

Continuous Spiral Flight Augers - The borehole is                   coring (nominal 52 mm diameter) is usually used with

advanced using 75 to 300 mm diameter continuous                     water flush. The length of core recovered is compared

spiral flight augers, which are withdrawn at intervals to           to the length drilled and any length not recovered is

allow sampling or insitu testing.            This is a relatively   shown as CORE LOSS.                The location of losses is

economical means of drilling in clays and in sands                  determined on site by the supervisor. If the location of

above the water table. Samples are returned to the                  the loss is uncertain, it is placed at the top end of the

surface by the flights or may be collected after                    run, when the core is placed in a storage tray and

withdrawal of the augers. Information from the drilling             recorded on the log.

(as distinct from specific sampling) is of relatively lower         Standard Penetration Tests - Standard Penetration
reliability due to remoulding, inclusion of cuttings from           Tests (SPT) are used mainly in non-cohesive soils, but
above or softening of samples by groundwater, or                    can also be used in cohesive soils, as a means of
uncertainties as to the original depth of the samples.              indicating density or strength. The test procedure is
Augering below the groundwater table has a lower                    described in Australian Standard 1289, "Methods of
reliability than augering above the water table. Various            Testing Soils for Engineering Purposes" - Test 6.3.1.
drill bits are attached to the base of the augers during


NOTES RELATING TO THIS REPORT - SEPT 2013                                                   SOIL SURVEYS ENGINEERING