Changes Application - MCU15/0023.02

                                                                -4 -

exist between         static   cone and         nearby borehole        GROUNDWATER
information.                                                           Where groundwater levels are measured in boreholes,
Portable Dynamic Cone Penetrometers                    - Portable      there are several potential problems.
Dynamic Cone Penetrometer (DCP) tests are carried                      •Although groundwater may be present in lower
out by driving a rod into the ground with a failing weight             permeability soils, it may enter the hole slowly or
hammer and measuring the blows for successive                          perhaps not at ail during the time the hole is open.
100mm increments of penetration.                                       •A localized perched water table may lead to an
The DCP comprises a Cone of 20 mm diameter with                        erroneous indication of the true water table.
30 degree taper attached to steel rods of smailer                      • Water table levels wiil vary from time to time with
section.                                                               seasons or recent weather changes and may not be
The cone end is driven with a 9 kg hammer falling 510                  the same at the time of construction .
mm (AS. 1289 Test 6.3.2). The test was developed                       • The use of water or mud as a drilling fluid will mask
initiaily for pavement sub9rade investigations, and                    any groundwater inflow. Water has to be bailed out of
empirical correlations of the test results with California             the bore and mud must be washed out of the hole or
Bearing Ratio have been published by various Road                      "reverted" if water observations are to be made.
Authorities.     The Company has developed their own                   More reliable measurements can be made by use of
correlations     with    Standard       Penetration    tests   and     standpipes which are read after stabilizing at periods
Density Index tests in sands.                                          ranging from several days to perhaps weeks for low
LOGS                                                                   permeability soils. Piezometers, sealed in a particular
The borehole or test pit logs presented herein are an                  stratum, may be advisable in low permeability soils or
engineering and/or geological interpretation of the                    where there may be interference from perched water
subsurface conditions, and their reliability wiil depend               tables or surface water.
to some extent on the frequency of sampling and the                    FILL
method of drilling or excavation.              Ideaily, continuous
                                                                       The presence of fiil materials can often be determined
undisturbed sampling or core drilling wiil enable the                  only by the inclusion of foreign objects (eg. bricks,
most reliable assessment but is not always practicable                 steel, etc.) or by distinctly unusual coiour, texture or
or possible to justify on economic grounds.                In any      fabric.   Identification of the extent of fiil materials will
case, the boreholes or test pits represent only a very
                                                                       also depend on investigation methods and frequency.
smail sample of the total subsurface conditions.                       Where natural soils similar to those at the site are used
The attached explanatory notes define the terms and                    for fiil, it may be difficult with limited testing and
symbols used in preparation of the logs.                               sampiing to reliably determine the extent of the fiil.
Interpretation of the infonmation shown on the logs,                   The presence of fiil materials is usuaily regarded with
and its application to design and construction, should                 caution as the possible variation in density, strength
therefore take into account the spacing of boreholes or                and material type is much greater than with natural soil
test pits, the method of drilling or excavation, the                   deposits. Consequently, there is an increased risk of
frequency of sampling and testing and the possibility of               adverse engineering characteristics or behaviour.          If
other than "straight           line" variations     between the        the volume and quality of fiil is important to a project,
boreholes or test pits. Subsurface conditions between                  then frequent test pit excavations are preferable to
boreholes or test pits may vary significantly from                     boreholes.
conditions encountered at the borehole or test pit
locations.




NOTES RELATING   TO THIS REPORT.   JUNE 2009                                                 SOIL SURVEYS ENGINEERING