Changes Application - MCU15/0023.02

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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
INVESTIGA TlON METHODS                                                        rods and the soil or casing, carrying the drill cullings.
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 ciay, 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 cUllings 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 onginal 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 allached to the base of the augers during


NOTES RELA rING TO THIS REPORT.    JUNE 2009                                                              SOIL SURVEYS          ENGINEERING