7/29/2019 Ashokan-Cross Hole Test

1/21

CROSS HOLE TEST FOR DETERMINING

DYNAMIC PROPERTIES OF SOIL

ASHOKAN KM2, GeoTech,

7/29/2019 Ashokan-Cross Hole Test

2/21

Introduction :

Dynamic properties are the properties of soil which

are needed in the analysis and design of a structure

subjected to dynamic loading.

7/29/2019 Ashokan-Cross Hole Test

3/21

(a) Dynamic moduli,

- Young's modulus E- Shear modulus G

- Bulk modulus K

(b) Poisson's ratio

(c) Dynamic elastic constants,- Coefficient of elastic uniform compression Cu,

- Coefficient of elastic uniform shear Cv,

- Coefficient of elastic non-uniform compression C

- Coefficient of elastic non-uniform shearC

Dynamic properties:

7/29/2019 Ashokan-Cross Hole Test

4/21

(d) Damping ratio

(e) Liquefaction parameters,

- Cyclic stress ratio,

- Cyclic deformation

- Pore pressure response.

(f) Strength-deformation characteristics.

Dynamic properties: ...Contd

7/29/2019 Ashokan-Cross Hole Test

5/21

Laboratory Tests:

Resonant column test,

Ultrasonic pulse test,

Cyclic simple shear test,

Cyclic torsional simple shear test,

Cyclic triaxial compression test.

Field Tests:

Seismic cross-bore hole survey

Seismic up-hole survey

Seismic down-hole survey

Seismic refraction survey

Vertical block resonance test

Horizontal block resonance test

Cyclic plate load test

Standard penetration test

TESTING METHODS

7/29/2019 Ashokan-Cross Hole Test

6/21

SEISMIC CROSS-BORE HOLE SURVEY

Based on the measurement of velocity of wave

propagation from one borehole to another.

Seismic energy is generated at the bottom of one borehole

and the time of travel of the shear wave from this boreholeto another at known distance is measured.

Shear wave velocity is then computed by dividing the

distance between the boreholes by the travel.

7/29/2019 Ashokan-Cross Hole Test

7/21

Multiple hole seismic cross hole survey (After Stoke and Woods, 1972)

7/29/2019 Ashokan-Cross Hole Test

8/21

Energy Sources

- P Wave Generators

Impulsive Sources- Explosives,

Hammer, Air gun

- S Wave Generators- Repeatable sourceReceivers

- Transducers

Geophones & Accelerometers

Recording System

- Separate Amplifiers for each transducer

- Display unit with digital signal filtering

Oscilloscope

Apparatus:

7/29/2019 Ashokan-Cross Hole Test

9/21

Crosshole TestingOscilloscope

PVC-casedBorehole

PVC-casedBorehole

Downhole

Hammer

(Source) Velocity

Transducer

(GeophoneReceiver)

t

x

Shear Wave Velocity:

Vs = x/t

Test

Depth

ASTM D 4428

Pump

packer

Note: Verticality of casing

must be established by

slope inclinometers to correctdistances x with depth.

Slope

I ncli nometerSlope

Inclinometer

7/29/2019 Ashokan-Cross Hole Test

10/21

Procedure

Borehole Preparation:

Three boreholes in line, spaced 3.0 m apart. It may be extended

to 4.5 m if higher velocity is expected.

Drill boreholes, with a dia not exceeding 165 mm. After thedrilling, case the boring with 75 /100 mm inside dia PVC /

aluminum casing.

Grout the space between casing & bore hole.

7/29/2019 Ashokan-Cross Hole Test

11/21

Cross hole Test:

Place the energy source in an end hole at a depth not greaterthan 1.5 m.

Place the two receivers at the same elevation in each of the

designated receiver holes and clamp firmly.

Activate the energy source and display both receivers

simultaneously on the recording device.

Repeat the test by lowering the energy source and receivers toa depth not greater than 1.5 m from the previous test locations.

During withdrawal of the energy source and receivers from

the boreholes, perform repeat tests at 6.0-m intervals.

7/29/2019 Ashokan-Cross Hole Test

12/21

Depth

in

Mtr

Travel Time in sec. Apparent velocity m/s

S R1 S - R2 R1 - R2 S R1 S - R2 R1 - R2

P S P S P S P S P S P S

Data Tabulation

7/29/2019 Ashokan-Cross Hole Test

13/21

Shear wave velocity versus depth from cross hole seismic survey

(After Stokes and Woods 1972)

7/29/2019 Ashokan-Cross Hole Test

14/21

Calculations:The various dynamic properties can be then determined by:

Youngs Modulus, E = Vc2 (1+) (1-2 ) / (1- )

Where, Vc = Velocity of compression waves in m/s

= Mass density of soil in N/m3

= Poissons ratio of soil

Shear Modulus, G = Vs2

Where, Vs = Velocity of shear waves in m/s

Coefficient of elastic

uniform compression, Cu = 1.13 E / [(1- 2)A1/2]

Where, A = Area of contact in m2Coefficient of elastic uniform shear, C = Cu / (1.50 to 2.00)

Coefficient of elastic non-uniform compression, C = 3.46 C

Coefficient of elastic non-uniform shear, C = 1.50 C

7/29/2019 Ashokan-Cross Hole Test

15/21

ADVANTAGES:

Gives detailed and accurate in situ velocity profile.

Permits exact interpretation of mode of propagation of the waves.

Assess the complex layered velocity structure.

For coarse-grained materials, it is the most acceptable

The only method that has an ASTM standard.

7/29/2019 Ashokan-Cross Hole Test

16/21

DISADVANTAGES:

Not applicable where hazardous subsurface conditions exists.

Difficult in loose, liquefiable sand and gravel type soils.

Requires minimum two bore holes and hence expensive.

7/29/2019 Ashokan-Cross Hole Test

17/21

Solgeo Hydrophonefor P and S waves generation

7/29/2019 Ashokan-Cross Hole Test

18/21

Electrodynamics transmitter for S waves GEOS-H (sx) Geophone receiver ATG-14 (dx)

and i ts relati ng pneumatic clamping system

7/29/2019 Ashokan-Cross Hole Test

19/21

I nclinometer Probe A15 (sx) and i ts Acquisition Unit (dx)

7/29/2019 Ashokan-Cross Hole Test

20/21

REFERENCES

1.Swami Saran, 1999, Soil Dynamics and Machine

Foundations Galgotia Publications Pvt. Ltd., pp119-183

2.ASTM D4428 / D4428M, (2000), Standard Test Methods for

Cross hole Seismic Testing

3.IS 5249, (1978), Determination of dynamic properties ofsoil4.IS 2810, (1979), Glossary of terms relating to soil dynamics

7/29/2019 Ashokan-Cross Hole Test

21/21

THANK YOU