direct-push crosshole (dpch) testing for high-resolution ... · 23/06/2016 · direct-push...

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



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


Direct-push Crosshole (DPCH) Setup

Source rod (S) Receiver rod (R)

V

H1

H2

V

H1

H2


Impact

P-wave

SHV -wave

P-wave

Trigger

P-wave

SHV -wave

1.5 – 2.0 m


DPCH for Ground Improvement



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


DPCH for Ground Improvement cont…

1.5 – 2.0 m


Impact

Stone column/RAP


DPCH for Ground Improvement cont…

1.5 – 2.0 mImpact


Stone column/RAP

20 cm

increments


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


20 cm

increments

SHV –wave arrivals complicated by refracted waves or non-direct travel paths

SHV –wave Arrivals P–wave Arrivals


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)


DPCH Distance Calculation

Triaxial MEMS accelerometer for tilt

and position calculations


DPCH at Port of Longview

0m

5m

10m

0m

5m

10m

Silt-Sand Mix

SandSand Mix

Silt-Silt Mix

DPCH


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

)


-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?

direct-push crosshole (dpch) testing for high-resolution ... · 23/06/2016 · direct-push...

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