dynamic soil properties -6th

Prof. Dr. Md. Mokhlesur Rahman Advanced Foundation Engineering - CE - 4303

Page 1 of 33

DUET

CE-4303

ADVANCED FOUNDATION ENGINEERING

NOTE NO 06

DYNAMIC SOIL PROPERTIES

PREPARED BY:

Dr. Md. Mokhlesur Rahman Professor

Civil Engineering Department Dhaka University of Engineering & Technology (DUET), Gazipur.


Page 2 of 33

Dynamic Soil Properties

The major soil dynamic properties are:

Shear strength (Su) evaluated in terms of strain rates and stress - strain

characteristics

Dynamic moduli, Young modulus E(Ev,Eh), Shear modulus G(Gmax) and

Constrained modulus

Poissons ratio (vh, hh, hv)

Damping (D)

Ev and Eh are equal for isotropic behavior of soil. Normally, Ev and Eh are not

equal because of fabric, characteristics of grains, particles orientation in a grain mass of

soil and geometric history of loading on soil mass. Always, Ev > Eh .

The majority of the numerous analytical methods presently available for

assessing the response of soil deposits or soil structure due to earthquake, explosion or

machine loading require and accurate assessment of maximum shear modulus (Gmax) in

the field, where Gmax is defined as the shear modulus at shearing strain amplitude less or

equal than 0.001 percent.

Also E is defined as the elastic Youngs modulus at strain amplitudes less or equal than

0.001 percent.

=

()

=

The is defined as the ratio of horizontal strain to vertical strain at shearing strain

amplitudes less or equal than 0.001 percent.

=


Page 3 of 33

0.001%

Figure - 30: Strain Stress curve

Dynamic soil test

The following tests are applied in laboratory or field for measuring the soil parameters:

Field test Parameter Obtained

Wave propagation test E,G,

Cross bore hole wave propagation

Up hole or down hole wave propagation

Surface wave propagation

Block Vibration test Cu, D, E, G, C

Cyclic Plate load test Cu,E, G

Laboratory Test

Cyclic tri-axial test E,G,

Wave Propagation test/wave velocity method E,G,

Resonant column test E,G,D

Cyclic Simple shear test

Cyclic Tensional Simple shear test

X-ray diffraction analysis/Ultra sonic pulse test

Air pollution method

Water submergence method

Wet compaction method


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Differences between dynamic test and static test:

Dynamic test Static test

1 It is monotonic or cyclic loading test with

relatively large strain rate.

It is monotonic or cyclic loading test

with relatively slow strain rate.

2 Inertia effect is considered. Inertia effect is not considered

3 Acceleration is a major controlling factor. Acceleration is not a major controlling

factor

4 The stiffens are found. The stiffens are not found.

5 Testing procedure are complex. Testing procedure is simple.

The term Dynamic loading is more general and it means monotonic or cyclic

loading at such a

Relatively large strain rate as the effect of inertia cannot be ignored. Therefore

Dynamic (loading) test refer to conditions where the acceleration is a major.

Controlling factor and the stiffness of specimen is determined by the dynamic

properties of specimen or system including a specimen (i.e. the wave velocity

within the specimen or the resonant-frequency or natural frequency of the

system).

Also, the modifier Static should not be equated exclusively with monotonic

virgin loading at a relatively slow strain rate.

The term Static (loading) test should be defined as monotonic or cyclic loading at a

Relatively slow strain rate where the effect of inertia can be ignored.

Hence, Static (loading) test refer to those in which both the stresses (and / or

loads) and the strains (and / or deformations) are measured under the conditions

without discernible effects of inertia.


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(-)

(+)

Time

(-)

(+)

TimeDouble Amplitude

0.001% Strain

Figure - 31: Strain and stress have same direction

The stiffness at which 0.001% strain is called young modulus, =

0

= 0


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30%

0.421

Small Stiffness

Granular Soil

Stiffness is increased withincreased vertical stress.1

0.50

Unique Relationship

Figure - 32: Shear modulus and Shear strain relationship

Definitions of several types of stiffness

E o

r G

()

()

()


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Secant Youngs modulus, = ()

Tangent Youngs modulus = ()

()

Secant Youngs modulus at = ( )

= =( )

Equivalent Youngs modulus = ()

()

qmax

Esec

0

Emax

Axial Strain

Dev

iato

r S

tres

s, q q0

1

1

1

2qSA

Eeq

E tan

Figure - 45: Plot of Deviator stress vs Axial strain

When the initial portion of the stress-strain curve is linear and the strain is fully

recoverable, we can see that

= = =

: Youngs modulus and shear modulus obtained from in situ elastic shear

wave velocity , which are

2()


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= 2(1 + )

= =

Where,

=

=

= = 980 /

=

qmax

0

E

q

1

max2

Figure - 46: Plot of Stress vs Axial strain


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Monotonic loading for overconsolidated soils and cyclicpresheareared soils, Drained

Cyclic Loading

-510

-410

-310

-210

-110

-610

G

Gmax

E

Emax

eq

Limit of elasticrespose in

monotoric loading.

Decay Curve

Monotonic Loading

Peak

Undrained cyclic loadingof saturated loose sandand M.C soft clay

Residul

Figure - 47: Plot of Linear elastic, elastic weak plastic, elastic-obvious plastic

cyclic loading

Eeq

1

E sec

0

Figure - 48: Variation of shear stress verses shear strain

(), ()


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In the engineering practice of soil dynamics, the in situ relationship between the

equivalent shear modulus, and single amplitude shear strain, under cyclic

loading conditions is estimated using the following methodology.

Geq

Gf

Gmax

Figure - 49: A method used to estimate the in-situ stiffness as a function of strain

for dynamic loading

Bore hole wave propagation:

In the method, the velocity of wave propagation from one surface boring to a second

subsurface boring is measured. At least two bore holes are required, one for the impulse

and one or more for sensors. As shown in figure the impulse rod is struck on top,

causing an impulse to travel down the rod to the soil at the bottom of the hole. The

shearing between the rod and the soil creates shear waves that travel horizontally

through the soil, to the vertical motion sensor in the second hole, the time required for a

shear wave to traverse this known distance is measured. There are four sources of major

concern is conducting cross-bore hole shear test:

The bore holes

The seismic sources

The seismic receiver

The recording and timing equipment

Al MahmudTypewriter

Al MahmudTypewriter


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Figure - 33: Schematic diagram of cross hole seismic survey technique

Major criteria for a seismic source are:

It must be capable of generating predominantly one kind of wave.

It must be capable of repeating desired characteristics at a predetermined energy

level.

= =

=

=

(/)

Now,

Shear modulus = =

Young modulus = = 2(1 + )

Where,

= Poissons ratio of soil


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= mass density of soil

v = velocity of shear wave

Up-hole or down-hole wave propagation method

Up-hole and down-hole tests can be performed by using only one bore hole. In the up-

hole method, the sensor is placed at the surface and shear waves are generated at various

depths within the bore hole. In the down-hole method, the excitation is applied at the

surface and one or more sensors are place at different depth (figure - 34) within the

hole. Both the up-hole and the down-hole methods give average values of wave

velocities for the soil between the excitation and the sensor is one sensor is used or

between the sensors, if more than one is used in the bore hole.

S2

S1

R

R

Up bore-hole Down bore-hole

S = SourceR = Receiver

Figure - 34: Schematic diagram of up bore-hole and down bore-hole technique for

wave propagation method

Up bore-hole method Down bore-hole method

=

=

=

Shear modulus = =

Young modulus = 2(1 + ) = 2

(1 + )


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Where,



v = velocity of shear wave

Expander Pump

Rubber Enpander Back Plate

3 componentgeophone

Recorder

WoodenHammer

TrigerGeophone Weight

Figure - 35: Equipment and instruments of down hole survey

Surface wave propagation method:

The Rayleigh wave (R-wave) travels in a zone close to the surface. An electronic

or other harmonic vibrator can be used to generate a steady state R-wave and the ground

surface can be deformed as shown in figure-36.


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x

S S

Figure - 36: Deformed shape of half space surface

One ray is down away from the centre line of the oscillator. One of the geophones

connected to the horizontal plate of the oscilloscope is fixed 30 cm away from the

oscillator along a ray drawn so that the sensing axis of the geophone is vertical. A

similar geophone connected to the vertical plates of the oscilloscope, is moved along

this ray, away from the oscillator. The sensing axis of the geophone is kept vertical until

the Lissajous figure on the oscilloscope screen becomes a circle. However, if the phase

angle is deferent than 90, the Lissajous figure is an ellipse, and for zero phase angle it

is a straight line. The distance, S between the two geophone is measured. This distance

is then measure of the wave length of the generated R-wave. The test is repeated with

the oscillators other frequencies of operation. In cases where uniform soils extend to

infinite depths and the Lissajous figure is a circle, the wave length, of propagating

waves is given by,

= 4

Velocity of shear waves,

=

In which is the frequency of vibration at which the wave length has been measured.

and of soil medium are calculated as follows

= 2(1 + )

=

=

Where,


= velocity of shear waves


Value of Poissons ratio of soil

0.05 for clay

Al MahmudLine

Al MahmudHighlight


Page 15 of 33

0.03 - 0.35 for sand

0.15 - 0.25 for rock

If compression waves are used, the

=

In which

= velocity of shear waves

S = Distance

T = corresponding time of travel of wave

Then Elastic modulus is determined by:

= ()()

()

Block Resonance Test

Block resonance test for determining modulus and damping values. A standard block

1.50.750.70 m high is cast either at the surface or in a pit 4.52.75 m at a suitable

depth (figure - 37) and is excited in both horizontal and vertical modes.


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For H Test

Motor Oscillator Assembly

For V Test

AccelerationPicks Up

Depth to beselectedConcrete (M50)

1 m min

1 m min

4.50 m

2.75 m

Figure - 37: Block Resonant test setup

Forced Vertical Vibration Test:

For the vertical vibration mode, two acceleration pickups are fixed on top of the block

as shown in figure - 37, so that they can sense vertical motion of the block. The

mechanical oscillator, which works on the principle of eccentric masses mounted on

two shafts rotating in opposite directions, is mounted on the block so that it generates

purely vertical sinusoidal vibrations. The line of action of the vibrating force passes

through the centre of gravity of the block. After a suitable dynamic force value is

chosen, the oscillator is operated at a constant frequency. The oscillator frequency is

increased in steps of small values, say, from 1 cycle up to the maximum frequency of

the oscillator, and the signals are recorded. The same procedure is repeated for the

various dynamic force values. All force level and frequency; the dynamic force should

not exceed 20% of total mass of the block and motor-oscillator assembly.

In case of forced-vertical-vibration tests, the amplitude of vibration, at a given frequency () is given by

=

In which represents the vertical acceleration of vibration in /.


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The coefficient of elastic uniform compression ( ) of soil is given by,

=

.

In which, =

= ,

= .

= (

)

.

=

()

In forced vertical vibration tests, the value of damping co-efficient, D of soil is given by the following equation,

=

Figure - 38: Determination Damping ratio from forced vibration test

Logarithmic decrement,

=

In which,

, = Two frequencies on the amplitude frequency plot at which the amplitude

is equal to

= Maximum amplitude


Page 18 of 33

= frequency at which amplitude is maximum, i.e. resonant frequency.

Cyclic Plate Load Test

The cyclic field plate load test is similar to the plate bearing test conducted in the

field for evaluation of the allowable bearing capacity of soil for foundation design

purposes. The plates used for tests in the field are usually made of steel and are 25 mm

thick and 150 mm to 762 mm in diameter. To conduct a test, a hole is excavated to the

desired depth. The plate is placed at the center of the hole, and load is applied to the

plate in steps-about one-fourth to one-fifth of estimated ultimate load-by a jack. Each

step load is kept constant until the settlement becomes negligible. The final settlement

is recorded by dial gauges. Then the load is removed and the plate is allowed to

rebound. At the end of the rebounding period, the settlement of the plate is recorded.

Following that, the load on the plate is increases to reach a magnitude of the next

proposed stage of loading. The process of settlement recording is then repeated.

Figure - 39: Nature of load settlement diagram for cyclic plate load test

Figure shows the nature of the plot of q versus settlement (S) obtained from a cyclic

plate load test.

Note that soil pressure,

= ,

,

=

= 1.13

() Kg/cm2


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= (1

)

1.13

=

2(1 + )

In which

P = Corresponding load intensity (Kg/cm2)

Sc = Elastic rebound (cm)

A = Contact Area

Magnitude of Cz can be obtained from the plot of q vs. Se from figure

Factors affecting stress-deformation and strength characteristics of cohesive soils

under pulsating loads or Factors affecting the dynamic properties of cohesive soils

-

Type of soil and its properties (for example - water content, and state of

disturbance)

Initial static (sustained) stress level

Magnitude of dynamic stress

Number of repetitions of dynamic stress

Frequency of loading

Shape of wave form of loading

One directional or two directional loading

Oscillatory simple shear test and its shortcomings

The simple shear device consists essentially of a simple box, an arrangement for

applying a cyclic load to the soil and an electronic recording system.

The box of Roscoe, which contains a square sample with a side length of 6 cm

and a thickness of about 2 cm, is provided with two fixed side walls and two

hinged end walls so that the sample may be subjected to deformations of the type

shown in figure - 40.


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x x

Figure - 40: Idealized Stress condition for element of soil below ground surface

during an earthquake.

A schematic diagram in figure - 40 illustrates how the end walls rotate

simultaneously at eh ends of the shearing chamber to deform the soil uniformly.

Test data from simple shear tests have been analyzed to determine shear

parameters, soil moduli and damping.

Shortcomings

Stress in a tri-axial compression test does not adequately simulate the field

loading condition.

During the earthquake, the normal stresses on this plane remain constant while

cyclic shear stresses are induced during the period of shaking.

+ = 0


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Shearing Chamber

Plan View

Soil Sample

End Plate Rotation Soil Deformation

Elevation

Figure - 41: Schematic diagram illustrating rotation of hinged end plates and soil

deformation in oscillatory simple shear

Typical SoilElement

x x

Base Motion

Rock

Figure - 41: Field Condition of soil

Field condition differs:

In the field, there is a cyclic reorientation of the principal stress directions. The

major principal stress is initially vertical and rotates through some angle , to the


Page 22 of 33

right and left of its initial position. In a tri-axial compression test, the major

principal stress can act only in either the vertical or horizontal direction.

In the field, the soil element is initially consolidated to condition.

In the field, deformations are presumed to occur under plane strain condition,

while in a tri-axial compression test, the intermediate principal stress is either

equal to minor principal stress during axial compression or equal to major

principal stress during lateral compression.

Bilinear Model:

Figure - 42: Stress Strain curve of Soil and Bilinear model

The shear-stress-strain relationship may as shown in figure 42.

The soil exhibit nonlinear stress-strain characteristics from the very beginning of the

loading cycle. For purposes of analysis, this behavior may be represented by a bilinear

model in figure - 42.


Page 23 of 33

The bilinear model is defined by three parameters

Modulus until a limiting strain,

Modulus beyond strain,

Strain,

When the direction of strain is reversed, behavior is again determined by the modulus

until a strain change of 2 has developed and the modulus again controls the

behavior. This pattern then continuous throughout the cycle.

Pendulum Loading Apparatus:

Point

New

App

arat

us R

adio

us 1

8'

Pil

ot A

ppar

atus

Rad

ious

7'

Load Gauge

Test Specimen

Adjustable reaction

Upper Cylinder

Deformation gauge

Spring, k = 250lb/inch, 6 inchlong, 3 inch dia

Hydraulic cylinders3 in bore, 3 in stroke

Lower Cylinder

Figure - 43: Pendulum Loading Apparatus:

Three pieces of equipment were designed for this purpose. One of the pieces of

equipment is the pendulum loading apparatus shown in figure - 43.

The apparatus utilizes the energy of a pendulum which, when released from a

selected height, strikes a spring connected to the piston rod of a hydraulic (lower)

cylinder. The lower cylinder, in turn, is connected hydraulically to an upper cylinder,

which is mounted within a loading frame. The time of loading for a pendulum loading


Page 24 of 33

apparatus is proportional to the square root of the weight of the pendulum and is

inversely proportional to the square root of the spring constant. In addition, the

maximum force is proportional to the first power of the distance the pendulum is pulled

back, to the square root of the spring constant, and to the square root of the weight of eh

pendulum. This apparatus, with a time of loading of between 0.05 and 0.015 was found

to be best suited for performing fast transient test.

The load gauge used with this equipment consisted of electric resistance strain

gauge, mounted on a metal ring. The strain introduced in the gauges was then in direct

proportion to the load. These load gauges can be calibrated under static load and can be

used in a dynamic test. Similarly a deformation gauge was constructed on a cantilever

metal strip with electric resistance strain gauges, mounted on one end while the other

end rested on an unmovable support. The strain introduced in the cantilever was a

measure of the deformation of the soil sample.

= 30 50% LL = 37 - 59% PL = 20 - 27%

Str

ess

(Kg/

cm)

Stress

1

2

4

3

00.04 0.08 0.12 0.16 0.20 0.24

Strain

Shear failure at 0.02 sec

Time, sec

Figure - 44: Time vs stress and strain in an unconfined transient test on Cambridge

clay.

From the typical test data presented above, it may be concluded that:

The strength of clays loaded to failure in about 0.02 s is approximately 1.5 to 2.0

times greater than their 10 - min static strength.


Page 25 of 33

Modulus of deformation, defined as the slope of a line drawn from the origin

through the point on the stress - deformation curve and corresponding to a stress

of one-half the strength, was about two times in the transient test.

These investigations suffer from the following short comings:

The dynamic load was not superimposed on a static load.

At best, the transient loading is adopted in the investigations represents only one

cycle of earthquake loading. Sometimes there may be as many as 100 peaks in an

actual earthquake.

Finally, the sands were tested while dry and dense. The effect of dynamic loading

on saturated loose sands may induce large pore pressures resulting in loss of

strength and consequent partial or complete liquefaction of sands.

This aspect of the problem is of great practical importance.

Resonant Column Tests

The Resonant column test for determining modulus and damping characteristics of soil

is based on the theory of compression waves or shear waves propagation in prismatic

rods. In a resonant column apparatus the exciting frequency is adjusted until the

specimen experiences resonance. The modulus is computed from the resonant frequency

and the geometric properties of the specimen and driving apparatus. Damping is

determined by turning off the driving power at resonance and recording the decaying

vibrations from which a logarithmic decrement is calculated. Alternative methods of

damping measurement include determining damping from the shape of the resonance

curve or determining a resonant factor from driving coil current measurements.

Several versions of the resonant column test are possible using different end conditions

to constrain the specimen. Some common end conditions are shown in figure (50).


Page 26 of 33

x

J

J0x

Rigid mass Specimen; non-rigiddistributed mass

Driving force

Weightless Spring

Specimen; non-rigiddistributed mass

Fixed Support

Deshpot

Weightless Spring

Rigid mass

(a) (b)

(c) (d)

Driving force

Figure - 50: Some common end conditions of resonant column test.

Each configuration requires slightly different driving equipment and methods of

data interpretation. The fixed free apparatus is the simplest configuration in terms of

equipment and interpretation as figure (50-a). Figure (50-a) the distribution of angular

rotation, , along the specimen is a

sine wave but by adding a mass with mass polar

moment , at the top of the specimen as in figure (50-b)the variation of along the

sample becomes nearly linear. The end effects to obtain uniform strain distribution

through the length of the specimen. The apparatus configuration in figure (50-c) can be

described as the spring base model. For a condition where the spring is weak

compared to the specimen, the configuration of figure (50-c) could be called free free.

A mode will occur at mid height of the specimen and the rotation distribution

would be a

sine wave. By adding end masses the rotation distribution can also be

made nearly linear. To study the influences of anisotropic stress conditions on shear

modulus and damping. Figure (50-d) has fixed base and a top cap that is partially

restrained by a spring and dashpot which in turn reacts against an inertial mass. For

1

4

=

= 0.50

()

()

(,) (,)

1

4


Page 27 of 33

= 1.0 tests, the inertial mass is balanced by a counter weight, but by changing the

counter weight, axial load can be applied to the specimen.

Tensional Resonant Column Test

The shearing strain on a circular cross section in a tensional resonant column test varies

from zero at the centre to a maximum at the outer edge.

To study the influence of shearing strain amplitude on shear modulus and damping a

hollow cylinder apparatus shown in figure (24) with a configuration.

J

x

Figure - 24: Tensional Resonant column test apparatus

(,))

(,))

1

4


Page 28 of 33

The average shearing strain on any horizontal cross section is not greatly different form

the maximum or minimum and shearing strain is uniform along the height of the

specimen.

Figure (24) also increased the torque capacity of the device to produce, large shearing

strain amplitudes,

For

Clay shearing strain amplitude up to 1%

Sand shearing strain amplitude up to 5% (for 40psi or 276KN/m2

confining pressure.)

Cyclic tri-axial compression tests

Cyclic test permit evolution of modulus, either as appropriate for the specific

test configuration and material damping. The field condition to be reproduced in a

cyclic loading test is shown conceptually in figure (25) but because apparatus that could

produce these stress conditions did not exist in the early stages of cyclic soil testing, the

cyclic tri-axial compression test was developed first.

Figure - 25: Cyclic shear test

In this test cylindrical tri-axial samples are initially consolidate under a cell pressure,

resulting in stress shown by condition 1, figure (26)


Page 29 of 33

Condition 1

Condition 2

Figure - 26: Stress Condition

In principle, the sample is then subject to an increase in axial stress

and a

simultaneous reduction in the cell pressure by an equal amount (condition -2, Figure-

26). The normal stress on the 45 plane through the sample is not changed but a

shearing stress of

is developed on that plane. The axial stress and cell pressure are

then simultaneously reversed by

so that the shearing stress reverses on the 45 plane

while the normal stress remains the same. These stress conditions are intended to be

similar to those experienced on a horizontal plane in an element of soil in the field. For

convenience the test is normally performed by maintaining the cell pressure at a

constant value and cycling the axial stress by as shown in figure (27).

Figure - 27: Constant Cell Pressure


Page 30 of 33

Figure - 28: Vertical load, vertical deformation and pore pressure record as a function

of the number of cycles of load

The technique results in essentially the same stress conditions as long as the

sample is saturated and tested un-drained. If samples are partially saturated or tested

with drainage, it is necessary to utilize axial and lateral stress control to simulate

earthquake loading. In the many versions of the cyclic tri-axial test, the configuration of

the specimen is standard but the loading and control equipment are variable. Most

currently used apparatus are stress controlled devices in which a cyclic axial load is

applied to an un-drained specimen.

Vertical load, vertical deformation and pore pressure are recorded as a function of

the number of cycles of load (figure - 28). Some of the more common load control

systems are the pneumatic, hydraulic, electro hydraulic and the pneumatic hydraulic.

Ver

tica

l Loa

d

Ver

tica

l Def

orm

atio

n

Po

re P

ress

ure


Page 31 of 33

In addition to liquefaction characteristics of soils, Youngs modulus, , and

damping ratio are often measured in the cyclic tri-axial test (Figure - 29) by

performing strain controlled tests. These tests are performed in essentially the same

manner as the stress controlled test, however, a servo system is used to apply cycles of

controlled deformation.

Figure - 29: Stress-Strain plot of strain controlled test

Youngs modulus is determined from the ratio of the applied axial stress to axial

strain.

For strained strain controlled tests, shear modulus is computed from, =

() in

which is Poissons ratio.

The cyclic tri-axial test has limitations among which are:

1. Shearing strain measurements below 10 percent are difficult to achieve.

Vertical Stress,

Vertical Strain

+

+

=

=

1

2


Page 32 of 33

2. The extension and compression phases of each cycle produce different results,

therefore hysteresis loops are not symmetric in strain controlled tests and samples

tend to neck in stress controlled tests.

3. Void ratio redistribution occurs within the specimen during cyclic testing.

4. Stress concentrations occur at the cap and base of the specimen and the major

principal stress changes direction by 90 during test.

Questions

on

Dynamic Soil Properties

1. Write down the name of major dynamics soil properties parameters with proper

symbols?

2. Define isotropic soil and homogenous soil? Practically is soil always isotropic?

Why?

3. Define shear modulus and Poissons ratio of soils.

4. What are field tests for soil dynamic parameter?

5. What are laboratory test for soil dynamics parameter?

6. Write down name and symbol for soil dynamics parameters that you will find by

test.

7. Draw the figure for cross bore hole wave propagation method.

8. What are four sources used for cross bore holes wave propagation method for

dynamic soil properties?

9. What the calculations are for cross bore holes wave propagation method?

10. Draw a figure for up hole and down holes wave propagation method.

11. Draw a schematic diagram for down-hole wave propagation method survey.

12. How will you calculate for down hole wave propagation method for dynamics

soil properties?

13. What are the calculations used for up bore holes method?

14. Draw the R-wave and define it.

15. What do you mean by Lissajous figure for dynamics soil properties

measurement? Draw Lissajous figure for dynamics soil properties measurement.

16. How will you calculate soil parameters from surface - wave propagation

method?

17. What are the factors affecting the dynamic properties of cohesive soils?

18. What are the differences between dynamic and static soil properties test?


Page 33 of 33

19. With graph define several types of stiffness used for soil.

20. Why is the average shear stress 65% of maximum shear stress?

dynamic soil properties -6th

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