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Direct-Push Crosshole (DPCH) Testing
for High-Resolution Vp and Vs Subsurface Profiling
Brady R. Cox1
Kenneth H. Stokoe1, Liam Wotherspoon2, Andrew Stolte1,
1Department of Civil, Architectural and Environmental Engineering, The University of Texas, Austin, USA2Department of Civil and Environmental Engineering, The University of Auckland, New Zealand
Longhorns
NHERI@Utexas In-Situ Liquefaction Workshop
Portland, Oregon; 23 June 2016
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 2
• Push two seismic cones ~ 0.75 – 2.0 m apart
• Propagate compression (P) and shear (S) waves
between the cones
• Measurements at 20 – 50 cm depth intervals
• High-resolution measurements of Vp and Vs down
to at least 20 m depth
• Vp measurements used to find depth to 100%
saturation (Vp > 1500 m/s)
• Can test native soil and improved ground
Direct-Push Crosshole Overview
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 2
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 3
Direct-push Crosshole Equipment
Full-sized track-mounted CPT rigand portable CPT actuator
Standard Seismic CPT Cone
Pagani track-mounted CPT rigs
Custom Built Cones:3 x orthogonal geophones
1 x triaxial MEMS accelerometer
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 4
Direct-push Crosshole (DPCH) Setup
Source rod (S) Receiver rod (R)
V
H1
H2
V
H1
H2
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 4
Impact
P-wave
SHV -wave
P-wave
Trigger
P-wave
SHV -wave
1.5 – 2.0 m
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 5
DPCH for Ground Improvement
Source rod (S) Receiver rod (R)
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 5
Impact
P-wave
P- & S-wave
S
R
S
R
Stone column/RAP
Between
SR
Composite
V
H1
H2
V
H1
H2
1.5 – 2.0 m
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 6
DPCH for Ground Improvement cont…
1.5 – 2.0 m
Source rod (S) Receiver rod (R)
Impact
Stone column/RAP
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 7
DPCH for Ground Improvement cont…
1.5 – 2.0 mImpact
Source rod (S) Receiver rod (R)
Stone column/RAP
20 cm
increments
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 8
DPCH for Vp and Vs
In-line horizontal
geophone
Vertical
geophone
(a) (b)
0 2 4 6 8 10
-8
-7
-6
-5
-4
-3
-2
-1
0
Travel Time (ms)
De
pth
(m
)
0 5 10 15 20
-8
-7
-6
-5
-4
-3
-2
-1
0
Travel Time (ms)
De
pth
(m
)
1.5 – 2.0 mImpact
Source rod (S) Receiver rod (R)
20 cm
increments
SHV –wave arrivals complicated by refracted waves or non-direct travel paths
SHV –wave Arrivals P–wave Arrivals
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 9
DPCH Trigger Calibration
tC = tRaw+ tT
V = Dist. / tC
0 5 10 15 20 25 30
-7
-6
-5
-4
-3
-2
-1
0
S-Wave Arrivals -548Bower Across2
Travel Time (ms)D
ep
th (
m)
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 10
DPCH Distance Calculation
Triaxial MEMS accelerometer for tilt
and position calculations
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 11
DPCH at Port of Longview
0m
5m
10m
0m
5m
10m
Silt-Sand Mix
SandSand Mix
Silt-Silt Mix
DPCH
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 12
DPCH Waveforms: OSU-5
0 5 10 15 200
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
XH P-Wave - Receiver Cone
Time (ms)
Depth
(m
)
0 5 10 15 200
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
XH S-Wave - Receiver Cone
Time (ms)
Depth
(m
)
Utilizing direct-push crosshole testing to assess the effectiveness of shallow ground improvementsB.R. Cox 13
-10 -5 0 5 100
1
2
3
4
5
6
FR
(%) & qt (MPa)
Depth
(m
)
0 1 2 3 40
1
2
3
4
5
6 Gra
vell
y
San
d
San
d M
ix
Sil
t M
ix
Cla
y
Org
an
ics
IC
0 500 1000 1500 20000
1
2
3
4
5
6
VP (m/s)
0 50 100 150 2000
1
2
3
4
5
6
VS (m/s)
DPCH Results: OSU-5
B.R. Cox 14
Questions?