Casing–Rock Driveability
Energy screening for driving steel casing to / into rock
← Hiley set analyser
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Project
Casing reference
Date
Recorded by
1
Casing
Outside diameter OD
mm
Wall thickness t
mm
Casing length L
m
Steel yield f
y
MPa
Helmet / anvil weight
kN
Steel modulus E
GPa
Toe condition
Open-ended, coring (bears on the wall annulus)
Plugged / closed end (bears on full face)
Shoe area factor k
sh
1.0 plain wall · 1.2–1.5 thickened / external upset cutting shoe.
2
Ground & rock
Overburden depth
m
Avg. shaft friction f
s
kPa
Loose fill/soft clay 10–25 · medium sands/firm clay 25–60 · dense 60–120.
Rock type
(sets a typical UCS)
Chalk / very weak calcareous (1–5 MPa)
Weak mudstone / siltstone (5–25 MPa)
Shale (10–50 MPa)
Weak sandstone (15–50 MPa)
Medium sandstone (50–100 MPa)
Limestone (30–150 MPa)
Greywacke, slightly weathered (100–200 MPa)
Basalt (100–300 MPa)
Granite (120–250 MPa)
Custom…
Unconfined compressive strength UCS
MPa
Toe resistance factor k
b
(q
b
= k
b
·UCS)
Massive / intact rock mass (3.0)
Slightly fractured (2.5)
Moderately fractured (2.0)
Heavily fractured / bedded (1.5)
Highly weathered / residual (1.0)
Custom…
k
b
value
Rock socket wall friction
(optional)
kPa
On a driven (smooth, disturbed) casing this is usually small — leave 0 unless you have data. Applied over the full target socket depth.
3
Hammer
Hammer type
(sets typical efficiency η
h
)
Hydraulic hammer (0.95)
Drop hammer — winch released (0.80)
Drop hammer — trigger released (1.00)
Single-acting air / steam (0.85)
Double-acting air / steam (0.85)
Diesel hammer (0.80)
Custom…
Hammer efficiency η
h
0–1
Ram weight × drop
Rated energy
Ram weight W
kN
Needed even in rated-energy mode (impact efficiency).
Drop height / stroke h
m
Rated energy per blow E
n
kJ
Typical hydraulic piling hammers: 60–300 kJ per blow.
Cushion / dolly condition
(sets coefficient of restitution e)
Steel ram direct on steel casing, no dolly (0.55)
Helmet + composite plastic dolly (0.50)
Helmet + timber dolly (0.30)
Custom…
Coefficient of restitution e
0–1
Cap compression c
c
mm
Rock quake c
q
mm
Casing elastic compression c
p
= SRD·L/(A
s
·E) is computed automatically.
4
Targets
Target rate
mm/blow
Rock socket depth
m
Blow rate
/min
Target rate is the penetration per blow you want to sustain; "practical refusal" here is < 0.5 mm/blow.
Predicted penetration per blow in this rock
—
mm/blow
—
Driving resistance SRD
—
kN
Energy needed for target rate
—
kJ/blow
Practical refusal at
—
MPa UCS
Toe steel stress
—
MPa
Socket production
—
min
Efficiency of blow η
b
—
Model
SRD = k
b
·UCS·A
bear
+ f
s
·π·OD·D
soil
+ f
sr
·π·OD·D
sock
then s =
η
h
· η
b
· E
blow
SRD
− c / 2
(Hiley energy balance, inverted)
Penetration rate vs rock strength
Table view
Penetration per blow for this casing + hammer as UCS increases. Hover or focus + arrow keys to read values.
UCS (MPa)
SRD (kN)
mm/blow
Blows/m
Verdict
Energy balance per blow
Section
W
helmet + dolly
casing
OD
overburden soil
D
rock
socket
qb