Environmental Engineering Reference
In-Depth Information
Table 5.3.
Drilling techniques and their applicability.
Approx. cost &
Drilling
Hole
Disadvantages and
Productivity (2001)
techniques
diameter
Support
Applicability
Advantages
precautions
$Australian
Auger drilling
Usually
Self-support i.e. the
Clayey soils, moist
Ease of setting up, rapid
Limited depth - 30 m
$40-50/m, 30 m/day
solid flight
100 mm
hole must support
sand above the
drilling, continuous
normal maximum. Not
with stopping for
itself
water table
disturbed sample
applicable for sandy
sampling
recovered
soils below water table
or soft clays because
hole needs support
Auger drilling
Usually 100
Self-support above
As above, and for
As above, can be used
Hollow flights are not
$50-70/m,
hollow
or 150 mm,
water table if augers
sandy soils and
below water table if
normally filled with water
20 m to
flight
up to
used as for solid
soft clays below
flights filled with water
or mud so “blowing” or
30 m/day for
300 mm
flight augers. Augers
the water table by
or mud. Easy sampling
disturbance at base of
100 mm
used to support
using the augers
Can be used in
hole may occur in granular
diameter
below water table
for support and
dam cores
soils and soft clays when
sampling through
withdrawing the plug in the
centre of augers
base of the augers for
sampling or testing
Rotary
75-100 mm
Self-support in clayey
All soil and rock
Allows full range of
Poor identification of soil
$50-60/m soil,
drilling -
common
soils. Casing and/or
types
sampling and testing
types in drill cuttings
$60-70/m rock
Non coring
drilling mud in granular
techniques. Rapid
Virtually impossible to
plus $50/m for
in soil &
soils and soft clays
drilling in rock
identify thin beds of sand
river gravel
rock (wash
Usually no support in
in clay. Proper identification
Good investigation
boring)
rock, but need mud if
requires tube or SPT samples
rotary drill rig with
rock is weak or highly
Unable to penetrate gravels
hydraulic top drive
fractured
efficiently. Must case or fill
and 3 m stroke
hole with water or mud to
Variable speed
prevent blowing in loose
head for augering/
granular soils and disturbance
coring. Truck
of soft clays. Note that even
mounted with 2 or 3
stiff clays can fail by shear at
winches to facilitate
30 m depth if not supported by
rapid removal of drill
mud. Rock samples difficult
rods for testing. Hire
(continued)
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