Environmental Engineering Reference
In-Depth Information
Table 5.3.
(Continued).
Approx. cost &
Drilling
Hole
Disadvantages and
Productivity (2001)
techniques
diameter
Support
Applicability
Advantages
precautions
$Australian
to identify in cuttings. May
rate is approx.
induce hydraulic fracture in
$150-170/hr
dam cores
Rotary
“N” hole
Hole is supported by
All rock types.
Continuous core of
Poor recovery in weak, friable,
NMLC or NQ3
drilling.
76 mm, “H”
casing through soil
With care good
rock. Continuous
and closely jointed rock. No
coring $80-90/m,
Coring in
hole 96 mm.
overlying rock. No
recovery can
“undisturbed” sample
recovery in clean sand and
HMLC or HQ3
soil & rock
Use “H” in
support in rock.
be achieved in soils
allows identification
silt. Soil and weathered rock
coring $90-100/m.
soil and
Water, mud or foam
with any cohesion.
of stratification in
samples usually disturbed by
10-15 m/day coring.
poor rock
used as drill fluid
alluvial soils.
stress relief and swell due to
To ensure best
water used from drilling. “H”
practicable core
size core gives better recovery
recovery drilling on
but is heavier and more
hourly hire is
expensive.
recommended. Rig
hire $150-200/hr.
Add $5/m for bit
wear
Reverse
Usually BQ
Outer casing of
Sands, silty sand,
Rapid drilling. Complete
Less commonly available.
Rig hire
circulation
Duo-tube
reverse
sand with fine
recovery of soil drilled
More expensive equipment.
$150-170/hr
(rotary)
equipment
gravel
(disturbed). Useful
Mixes strata. No testing or
plus compressor
for investigation
undisturbed sampling possible
hire. Up to 30 m/hr
of sand sources
Cable tool
Up to
Casing which may
Sands, gravel, clay,
Can penetrate gravels.
Slow drilling. Results
$80-100/hr. 2 m/hr
percussion
750 mm
or may not be
rock (fractured)
Can drill large
in strata mixing, breakage
down to 0.10 m/hr
bit and
recovered
diameter hole.
of rock fragments and loss
bailer
Simple equipment.
of fines which can give
misleading particle size
distribution. Very heavy tools
for transport and handling
Cable tool
Up to
Casing usually
All soils and weak
Provides continuous
Slow drilling. Very heavy
Rig Hire $80-100/hr.
tube
200 mm
recovered
rocks
samples and useful
tools for transport and
2 m/hr down to
groundwater data.
handling.
0.10 m/hr
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