seismic wave velocity as a means of in-place density...

1'

IOWA !:ll:PAR.Tl'\nEM'f OF TRANSPORTAT\0\\1 U3P ... Il_R.Y

C:OJ LINCOlN WAY AMES, IO'Ifv'A 50010

ENGINEERING RESEARCH INSvriTUTE

IOWA STATE

UNIVERSITY

AMES. IOWA

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, The opinions, findi11g~; and conclusions expressed in this publication are those· of the authors iand not necessarily those of the Iowa State Highway Commission nor the Bureau of Public Roads. ERI - 421 Project- 581 - S

ENGINEERING· •. 1. • . :· , ••....• ' •. :

·--RESEARCH I ~· ' • ' ' I

ENGINEE.RING ·RESEARC.H • ' I • 1 • '< I

ENGINEERING .RESEARCH

!

ENGINEERING RESEARCH ENGINEERING . . .;• . '

RESEARCH

FINAL REPORT :. PART 1 OF 2

.SEISMIC WAVE VELOCITY AS A ME4NS OF IN-PL~CE DENSITY MEASUREMENT . . '. •'

Prolect HR- 114 of the Iowa Highway Research Board ·' ·

,. conducted by Engineering Research Institute, Iowa

State Un i versiJy · · for ·

Iowa State Highway Commission if'l cooperation with Federal Highwqy

Administration Bureau of Public Ro.ads

, . Co-Proj,ect Directors , ·. J.M.Ho?ver, Associate Professor of Civil :Engineer!n~

R.L. Handy, Professor of Civil l;l']gin~ering

Contribution No. 68 • 8ci of the Soil . · Research Laborqtory ·

EN~INEERING RESEARCH INSTITUT~

· I 0 W A S T ~ T E U N !·V E R S I T Y

SEISMIC WAVE VELOCITY AS A .MEANS OF IN-PLACE DENSITY MEASUREMENT

J. M. Hogan and R. L. Handy

INTRODUCTION

The objective of this investigation was to apply principles of

first-arrival seismic refraction to the problem of determining in-place

dry density in·a soil embankment. The seismic refraction technique is a

method by which velocity of a seismic wave is obtained by measuring the

time for the wave to travel between known distances measured on the i

ground :surface. The laboratory method of study involved correlation of I

results of seismic wave measurements with conventional dry density and

moisture content measurements of several soils. Field seismic measure-

ments were correlated to in-place moisture-density determinations. The

ultimate goal was an economic improvement in construction control testing,

since the time required to perform an in-place seismic measurement on an

embankment in much less than that required for conventional moisture-

density determination.

REVIEW .OF LITERATURE

Seismic test methods are based upon properties of a material that

govern the propagation and dissipation of stress waves. The theory of

transmission of impulses through a solid body was first examined in con-

1 nection with propagation of earthquake waves • Other investigations have

. ' centered on theoretical considerations and experimental results related

to waves produced in a soil mass by vibrating foundation loads 2 • There

have been two general approaches to the study of soil properties by

.,

J

----------------------------------------------------

2

dynamic methods. One involves the application of a ,vibrational load to

the soil, while the second is based upon inducing a single sonic pulse.

A summary of the results obtained by different applications of the vibratory

method to the study of in-place properties of highway structural components

has been reported by Jones and Whiffen3 . Investigations utilizing the

vibratory method have generally been directed towards problems of road

design. There is no general agreement on the most pertinent dynamic

properties, and a sat is factory general method· of road design has not

been developed.

Goetz applied sonic testing techniques to specimens of asphaltic

concrete to study the correlation between resonant frequency and asphalt

content4. A problem with such measurements is that resonant frequency is

a function of specimen size, in addition to the physical properties of the

specimen. Other studies relate resonant frequency of portland cement

concrete to strength and durability5

Numerous engineering applications have utilized velocity measurements

of a single sonic pulse. For materials such ·as concrete, asphalt, wood,

metals, and polymers, the technique provides a means of quality testing.

Whitehurst summarized pulse velocity techniques and equipment for testing

t t t d t t k d d . . 5,6 concre e s rue ures to e ec crac s an eter~orat~on • Leslie investi-

gated samples of soil, wood and concrete by using pulse techniques, and

found that maximum velocity occurred in a silty clay at conditions of

. 7 optimum moisture content and maximum dry density• • Manke and Gallaway

showed that for a natural clay and a silty clay, maximum velocity oc

curred slightly on the dry side of optimum moisture content8

• The ef-

fects of confining pressure and temperature were also studied. As

3

confining pressure 'increased, pulse velocity ge.nerally increased~ Above

freezing, temperature had little or no effect, and below freezing, the

wave velocity greatly increased for soils that contained moisture.

Moore studied the relation of seismic wave velocity to degree of

densification for several soils and crushed stone 9 . Tests were con-

ducted under both field and laboratory conditions and results showed a

comparatively straight-line relation of seismic wave velocity to in-

creasing density. The equipment used was a Model MD-1 seismic unit

manufactured by Geophysical Specialties Division of Minn~tech Labs, Inc.,

Minneapolis, Minnesota. The relationship of seismic velocity to amount

of compaction given an in-place soil was studied at the Illinois Institute of

Technology Research Institute. Seismic equipment similar to that men-

tioned above was used, and results showed velocity generally increases

. . 10 with number of passes of compaction eqm .. pment •

Phelps and Cantor developed a microseismic refraction system to ' 11

study concrete deterioration under asphalt overlays TJ;lis approach

enabled the thickness of the overlying asphalt to be determined and the

quantity of the underlying concrete to be estimated by a nondestructive

test. The length of the refraction.line was about 3 ft,·whereas the common

length for a shallow subsurface investigation is often 100 to 200 ft.

METHODS

The first part of the investigation was to develop a technique ap-

plicable for measuring seismic velocities at small distances in both

laboratory and field. An adV)antage of determining velocity from a

distance-time graph is elimination of inacurracies due to delays in the

---- ------------

4

timing system. A relationship of pulse velocity to dry density and

moisture content was obtained by-laboratory measurements on standard

and modified AASHO compaction samples.

Equipment used for making shallow subsurface seismic investigations

consists of three components; ioe., seismic timer, transducer, and impact

source. The. timer measures el~psed time fo·r a seismic ·wave to travel

from the impact source to the transducer. For geophysical studies the

impact source can be a sledge hammer or explosive charge, and the trans

ducer is usually a geophone. When a hammer is used, energy is often

transmitted into the ground through a steel plate or ball.

The investigation began by using a Model MD-3 refraction timing

system obtained from Geophysical Specialties Division of Minnetech Labs,

Inc., Minneapolis, Minnesota, Fig. L Because of the short seismic line

length required, some equipment modifica.tions were made: a tack hammer

was ·used, and the energy couple was a 5/8-in. diameter steel ball bearing.

To make sure the timer started counting exactly when the hammer blow

generated the seismic wave, the timing circuit was modified to close at

the contact of the hammer and the ball bearing. This equipment gave ac

ceptable results in the field where a 3-ft seismic l~ne was used, but not

in the laboratory where maximum distance was about 4-1/2 in. The ~ounter

recorded time to the nearest one-tenth millisecond, adequate in the field

but inadequate in the laboratory, causing nonreproducibility of results.

Part of the latter was thought due to inconsistencies of hammer energy, .

but a miniature drop hammer failed to ejlleviate the problem. It was also

difficult to adapt the geophone to produce reliable first-arrival detections

when mounted on a proctor specimen.

5

The above described seismic refraction system was similar to that

9 used by R" W. Moore , Bureau of Public Roads, for finding in-place

velocities using a 5-ft seismic line and by the Illinois Institute of

Technology Research Institute, where the velocity measurements utilized

10 a line 2 ft long

A second refraction system used was a Model 217 Micro-Seismic Timer,

available from D,Ynametric, Inc., Pasadena, California, in which the

counter is controlled by a stable oscillator measuring travel time in

microseconds, Fig. 2. Common flashlight batteries provide power. The

transducer was a phonograph needle mounted in a·brass case, supported

on three rubber feet, Fig. 3. Needle contact pressure is controlled by

a leveling screw attached to one of the feet. The impact device and

energy couple were the same as used with the refraction system-previously

described. Tapping the ball bearing with the small hammer gave reproducible

results and a constant energy source was not necessary. This microseismic

apparatus allowed the field and laboratory pulse velocity measurements to

be made by the same equipment and technique.

Field measurements of microseismic refraction tests were made along

a 2-ft line divided into 3-in •. stations. To provide ~ood contact between

the transducer and soil, a l-in. flathead wire nail was driven flush

into the soil and the needle placed in contact with the nail. At each

station the ball bearing was seated into the subgr:ade to a depth one-half

its diameter and was not ):apped hard enough during the testing to drive

it deeper into the subgrade. At each station 10 first-arrival measure-

ments were recorded. Standard rubber balloon volumeasure density and

moisture content determinations were then made at midpoint of the seismic

I

I

!

6

Fig. 1. Geophysical specialties Model MD-3 refraction seismic unit.

Fig. 2. Dyna Metric Model 217 Microseismic Timer.

Fig. 3. Dyna Metric ceramic transducer.

Fig. 4. Laboratory specimen with transducer mounted.

7

line. Pulse velocities were calculated using data obtained from distance-

time plots. Analysis of field velocity plots was accomplished by

methods· common to shallow seismic investigation.

In the laboratory, standard and modified AASHO compaction tests were

performed on soil samples obtained from material used in the field em-

b k . 11 an ment construct~on • The specimen size was 4 in. diameter by 4.58 in.

high, produced in a split mold in order to minimize specimen disturbance

during removal. Two variations of the AASHO compaction procedure were

used in molding specimens. Specimens noted as "remolded" were prepared

by successive addition of water to the original soil. Specimens_ noted

as "nonremolded" were prepared by adding calculated amounts of water to

individual batches of soil. Moisture was added to the nonremolded

laboratory soils 24 hours before molding. Initially moisture was added

to the remolded soils 24 hours before molding with successive additions

of water prior to molding each specimen. Data from these tests were

used to express velocity as a function of dry density and moisture content

at constant compactive effort and curing time. i

For laboratory measurements, each sonic pulse was induced by striking

a ball bearing embedded to about one-half its diameter in the center of

the specimen. The. transducer was attached to the specimen by rubber

bands with the needle placed in contact with the head of a straight pin

embedded flush into the specimen surface. Four pins, cut to a length of

1/8 in., with heads roughened to provide a better contact surface, were

placed in a straight line parallel to the axis of the specimen and spaced

at 1/2-in. intervals, with the top pin 2. 7 in~ below the top o~ the specimen,

Fig. 4. Three such lines were spaced 120 degrees apart on the specimen

.-------~---------------------------------

8

surface with travel distance~ being measured from the bottom of the ball

bearing to the heads of the 'pins. At each transducer location, 10 time

measurements were recorded. For each specimen, three pulse velocities

were thus computed from the inverse slope of the distance-time plots and

the pulse velocity of the specimen was taken as the average value.

THEORY

The elastic properties of matter may be described by various elastic

constants. These include:

L Young's modulus (E), or modulus of elasticity, a measure of

the ratio of stress to strain in simple tension or compression.

2. Bulk modulus (k), a measure of the stress-strain ratio under

hydrostatic pressure •.

3. Shear modulus (n), a measure of the ratio of stress to strain

during shear.

4. Poisson's ratio (~), a measure of the geometric change of shape

of a materials mass.

The theory of elasticity indicates that a material can transmit two

principal .types of seismic.waves, longitudinal and transverse, each having

different speeds of propagation dependent on the elastic constants.

Longitudinal (compression) waves create a particle motion parallel

to the direction of propagation. These waves are similar in effect to I

sound waves in air. The velocity of longitudinal waves may be determined

by

-v L ~1

where p is the deQsity of the material.

(1)

----------------------------------,

9

Transverse (shear) waves create a particle. motion perpendicular

to the direction of wave propagation. They may be considered similar to

the waves of a vibrating string. The velocity of transverse waves may

be determined by

E 1 2

~ ~1:,

VT = p 2 (1 + IJ.) (2)

where again p is the density of the material.

Of the three variables, E, p, and IJ., the latter or Poisson's ratio,

is most nearly a constant. If 1-1 = 0.5 there is no volume change under

stress -that is, the volume expansion transverse to the stress equals

the volume decrease in the direction of applied stress. In soils 1-L is

about 0.4 to 0.5. Substituting a value of 0.44 into Eqs. (1) and (2)

gives:

{[p VL = 1.80 J p

mp YT 0. 59 J p

or VL/VT = 2.4. Thus the instruments available, which record first ar-

rival times, will record longitudinal waves unless the receiving instrument

can be arranged so longitudinal waves will not affect it.

Let us now re-examine Eq. (1). According to this equation, the

higher the density the lower the seismic velocity. This is opposite

what was observed in subsequent tests. We therefore may conclude that

density is not a major primary fact9r affecting seismic velocity. Or

stated another way, seismic velocity is not a direct measure of soil

density, since the effect of changes in density apparently is overridden

by changes in the modulus of elasticity E and/or Poisson 1 s ratio 1-L•

10

This means that the correlation between density and velocity will be

empirical, and will be influenced by anything which will change E and ~· .

Possible variations include:

• Moisture content

• Soil microstructure

• Degree of saturation

• Soil minerals

• Structural defects (cracks, spalls).

Thus a correlation may be suitable for a particular soil, moisture

conte'nt, method of molding, and elapsed time after molding. Hopefully

a meaningful correlation will be obtained on laboratory Proctor size

specimens for use in the field.

MATERIALS

Initial in-place seismic velocity tests were performed on highway

embankments constructed of three types of soil. Haterial for the

laboratory measurements was sampled from the embankment side-slope

adjacent to the area of field tests. A description of the materials

follows:

Wisconsin age glacial till, an A-4(5) clay loam located in range

23 west, township 83 north. Embankment of south-bound lane of Interstate 35

near junction of US 30. Liquid limit 23, plasticity index 9. Hereafter

referred to as I-35 till.

Kansan age glacial till, an A-6(10) silty clay located in range 30

west, township 75 north. Reconstruction embankment of Iowa Highway 92

seven miles east of Greenfield, Iowa. Two .. weathering variations were

11

tested, referred to hereafter as Greenfield till-gray or Greenfield till-'

brown. For gray, liquid limit 30, plasticity index 13; for brown, liquid

limit 40, plasticity index 18.

Loess, an A-4(8) silty loam located in range 44 west, township 77

north. Embankments of east and west bound lanes of Interstate-SO one

mile east of Loveland, Iowa. Liquid limit 32, plasticity index 6o

Referred'to hereafter as I-80 loess.

Much of the laboratory developmental work was done on a laboratory

loessial soil labeled as 20-2, which is similar to the I-80 loess. Results

obtained with the 20-2 loess will be shown with those of the I-80 loess

because of,the close similarity of the two materials.

LABORATORY RESULTS

Velocities measured in specimens obtained 'in the standard moisture-

density tests were plotted versus moisture content and versus dry density.

Typical curves are shown in Figs. 5 and 6.

Moisture Content

It will be noted that the moisture-seismic velocity curves' do not

peak out at the same place as the moisture-density ~urves; therefore.

seismic velocity cannot be used to establish optimum moisture content

without some correction. In general a maximum velocity occurred with

less than the optimum moisture content and with a correspondingly lower

dry density. The average difference in moisture contents for maximum

velocity compared to maximum density was 1.2 ± 0.86%, the .±entry indicating

}J,

I

+-'

u 0 (!)

>

~ u ci.

>. +-' If)

c <!J

0

>. L

0

122

120

118

116

12

/+\ +

\ +

Content, 0 /o

100 104 108 112 116

Dry Dens1ty, p.c.f:

Greenfield Till - Brown

AASHO Standard

AASHO Modified

o---o

+--· -+

Fig. 5. Greenfield till -brown.

120 124

"

+

J I - +

~2500 >.

+-'

(+\ - ·/+ \ u ci.

+ ~ +I

+-'

If) I c (!)

J 0

>. L

0 0

/. 96

------------------------------------------,

13

o/o

+ ;, if

/

100

Dry

+

104 108

Dens1 ty,

1-80 Loess

112

p.c.f.

AASHO Standard o-----0

AASHO Modified +--+

Fig. 6. 1'"'80 loess.

+

116

14

one standard deviation from the meano Data are shown in Table 1. Seismic

velocity could therefore be used to determine the optimum moisture content

for maximum density, but there appears to be little advantage in doing

so. The difference in optimum moisture contents does not seem to depend

on soil type or whether standard or modified compactive effort was used.

These results agree with those of Manke and Gallaway in which maximum

velocity occurred at a moisture content of about 1.5% less than optimum8

15

Table L Summary of laboratory results.

Soil

1~35 till

1-35 till

I-35 ti 11

I-35 till

Compaction proc~dur<'

Stnndard remolded

Modified remolded

Standard not remold~d

Modified not remolded

Greenfield Standard till -brown remolded

Greenfield Modified till - brawn not remolded

Greenfield Standard till - gray remolded

Greenfield· Modified till -gray rE'molde,d

Greenfield Standard till - gray not remolded

Greenfield Modified till - gray not remolded

1-80 loeaa St~ndard

remolded

I-80 loess Modified

I-80 loess

zo-z loPss

20-2 loess

20-2 loess

20-2 lOP88

remolded

Standard not remolded

S~andard

remolded

Modified r<'molded

Standard not remolded

Modi fi<'d not rl.'mo1dl'd· •

M;Jx. dry dt•nsity

(pc f)

123.3

131.0

122.4

lJl.O

ll0.2

125.3

116.7

127.7

115.3

126.1

109.3

117.7

106.8

107.0

116.7

105.8

lt4. 6 '

Dry dens! ty at maximum velocity

(pcf)

123.3

131.0

121.8

130.0

107 .o

123.8

114.6

126.6

113.4

124.7

106.2

106.5

103.5

116.7

112.2

Optimum moisture cont<'nt

(%)

10.3

7.~

10.8

8.8

16.0

11.5

13.5

9.2

l7. 5

12.5

16.0

17.4

[],1,

17.5

13.8

Moisture content at maximum ve.locity

(7.)

10.3

7.9

10.4

8.0

u~.5

12.5

11.7

8.0

13.1

9.1

14.0

10.6

1s.o·

16.2

13.4

15.4

12.6

Mnximum velocity

( fps)

2190

3570

3330

4180

3130

4480

3300

4040

3388

4140

1970

4160

1780

2780

3820

1830

3120

Velocity at maximum dry density -optimum moisture

content (fps)

3570 (a)

2950

2800

3000(a)

4330 (a)

2990(a)

2610

3400

1520

2680(a)

1520

1250

2780

(a)For th<.>BI.' teats the ve1ociti<'B wr:>rt• computl'd from tho> avt•ra~<· of two m<•nsuro>ments on t'Bt'h HpE'dmt>n. For all oth<'r t<'Sts an avl.'ra!!" of three ml'asun•mt•nta w<•rt• used 110 atnlt•d in tht• dt•vPlopml'nt of ml'thod st•.c t ion.

16

Density

The plots on the right in Figs. 5 and 6 show rather conclusively

that seismic velocity cannot be used to predict dry density if the

moisture content varies, as it does in these graphs. In orqer for the

density to be tested, one must determine the moisture content and go to

velocity versus moisture content curves to determine whether the velocity

is above or below the appropriate compaction curve.

Discussion

At a given moisture content a higher velocity is not always indicative

of a higher density. For example, in both·Figs. 5 and 6, at high moisture

contents the velocity is lower for •modified than for standard compaction.

This may be an advantage, since the seismic velocity thus appears to be

very sensitive to overcpmpaction, de fined as dispersion of clay due to re-

ld . h. h . 12 mo 1ng at too 1g a mo1sture content • According to theory, overcompac-

tion breaks the flocculated clay structure and allows clay particles to

become separated by liquid water, greatly weakening the soil shearing

strength. Overcompacted samples sometimes show internal slickensides, or

shear planes. This explanation appears to be consistent· with the decrease

in seismic velocity in this range, since it indicates a large reduction in

E, as was found in static tests by Seed and Chan12• Seismic velocit~

therefore could be more reliable than density as an indicator of satis-

factory compaction, since the density does not ordinarily reflect damages

from overcompaction.

I

17

Elapsed Time

Another phenomenon discovered more or less by accident was a gradual

decline in seismic velocity of laboratory specimens as they were aged.

This decrease occurred even though there was no appreciable change in

moisture content or density. Typical results are shown in Figs. 7, 8

and 9. Upon aging, the velocity peaks tended to become less pronounced

and move to a lower moisture content. The reason for this can only be

conjectured, and must relate to a .reduction in either E or ~. since p

remains essentially constant. The reason may relate to a gradual rear

rangement of the soil water; the clay mineral in all three soils is

montmorillonite, which readily absorbs water by interlayer expansion.

Incorporation of pore water into the clay interlayer structure might

soften the clay and reduce E and v1 • The opposite effect is expected

from thixotropic behavior, or the tendency for remolded and partially

dispersed soil clay to reflocculate with time. According to Barkan12 ,

moist clay has a high v1 • The explanation for the decrease in seismic

velocity therefore may relate to a change in ~· According to Eq. (1),

if 1-L should decrease from 0.44 to 0.42, which is not unlikely with a

removal of pore water, V1 would become 1.?0 ~/p, a decrease of over

10%. (Incidentally the shear wave is much less affected, decreasing

less than 1%.) The circums'tantial evidence therefore points to small

time-'dependent reductions in ~ gradually reducing the longitudinal wave

velocity. The practical significance is that velocity tests should be

made the same day that compaction is p~rformed or the velocity will be

lowered to the extent that the compaction may not pass a·velocity-criterion

specification.

r.

0.

>~ +-' ·o 0 1500

~

124

122 -u 121 0.

~ +-' C/) c QJ

0

.>, L

0

I ..

~

I

\ \ \ \

• I ' I \ I • I I I . I \ i I

\ I

I

--------------------------------------------------------.

18

·-- I

I .... ..._ ... :._____ / ------ . / .. __ , I-· ....

/ \ I '

Dry Density~

1- 35 Till

AASHO Standard·

o Day o o

2 Day +-----+ 8 Day •·-·-· •

Fig. 7. I-35' till.

I • I I

I /

. I .

I .

p.c.f.

• I

·-0 d.

" >. +-' c Q;

0

>. 122

L 0

I

I I I I.

+,

' \ \

\ \

\ \ ~ \

+ \

\

~

7 8 9 10 11 12 1~ 14 15

7 8 g 10 11 12 13

tv16is tu re Content J o I o

19

+----------+ . I

I I I ·---------··, ~ .....

...-"'\ ..... . ,....,........ \

,....

p.c.f.

1-35 Till

AASHO Modified:

0 Day ()...----()

2 Day +---'-+ 7 Day ·-·-·•

Fig. 8. I-35 ttll.

r-1

ci.. -

. -. u

112

102

ContentJ 'o/o

20

,.•.......... . .......... ...-................. ,/ ............ .... .. --

/ ·, _ ...... :_A- -._/ /. %.--- ......... _ ....... _.

A-/._ ____ A, ,"r 'A /

,· .... , ' ' . - '~

20- 2 Loess

AASHO Modified : 0 Day o---o 2 Day A----A

9 Day ·--·-•

/

'' I ', ' ' I A

Fig. 9. 20-2 loess.

21

FIElD DATA

Results from'35 field tests are shown in Figs. 10- 18. The

velocities obtained from these graphs are shown in Table 2.

In order to convert the velocity measurements to densities, the

laboratory moisture-density and moisture-velocity curves with standard

and modified compactive efforts were interpolated for intermediate com

pactive efforts, as shown in Figs. 19- 22. The curves for remolded

soils were used since they were less erratic, probably because of more

uniform pulverization. The compactive efforts were arbitrarily numbered

1 through 5, 1 indicating standard Proctor and 5 modified Proctor com

paction" Each measured velocity and moisture content was then entered·

on the moisture-velocity graphs and the compactive effort estimated.

The compactive effort and the moisture content were then entered on

the moisture-density curves to estimate dry density.

As seen in Table 2, in almost every instance the density inferred

from seismic data were lower than that actually measured in the field.

Exceptions are noted in parentheses, and all occur at high moisture

contents where there is an inverse relationship between velocity and

compactive effort. Thus in all cases the field velocities were toe;> low,

E_robably because no attempt was made to test immediately following compaction.

Exceptions were tests 30 to 32, which were t~sted im~ediately after

compaction. Unfortunately, in many of the tests the moisture content

was high enough to be in the region of an inverse vel'ocity-compactive

effort relationship, indicated by crossing of the lines. at the right in

Fig. 11. Interpolation of compactive efforts is. not appropriate in this

region, since the velocity probably peaks out at some intermediate effort

before overcompaction occurs.

-E 1.o

I- 0.4

0.2

(/)

-o c

0

0 1.6 u (1) 1.4 (/)

.= 1.2

. ~0.8 (1)

E o.6 1- 0.4

1-35 Till Dry Density :129.5 p.c.f.

Moisture Content : 8;5 •t.

+

0.5 1.0 1.5 2.0

D 1 s t a n c e, ft.

1-35 Till Dry Density :125.4 p .c. f.

Moisture Content : 8.6 •t.

0.5 1.0 1.5 2.0

D1 stance, ft.

Fig. 10.

(/")

\J c 0 u

~

-

2.0

I- C!l.4

0

(/)

-o c 0 u

2.0

1.8

C!J <.f1 1.2

0

I-35 till.

1-35 Till Dry Den~ity :129.0 p.c .f.

Moisture Content: 8.9 •t.

0.5 1.0 1.5

D1stance, fL


Moisture Content: 8.1 •t.

0.5 1.0 1.5

D1stance, ft.

•.

2.0

2.0

N N

c/)

u c 0 u (!.) c/)

E

c/)

u c 0 u (!) c/)

0.2

0

0

1-35 Till Dry Density : 130.2 p.c.f.

Moisture Content: 8.5 °/o

0.5 1.0 1.5

D1 stCince, ft.

1-35 Till Dry Density :.130.1 p.c.f.

Moisture Content : 6.9 °/o

0.5 1.0 1.5

D1 stCince, ft.

2.0

2.0

c/)

u c 0 u Q.; c/)

-= 1.0

c/)

'0 c 0 u

·<M

0

I- 35 Till Dry Density :124.2 p. c. f.


0.5 1.0 1.5

D1stC1nce, ft.


Moisture Content: 8.6 °/o

Fig. 11. I-35 till.

2.0

N w

ell 1:)

c 0

ell 2.0 1:)

c 1.8 0 u (!)

ell

0

t- 35 Till Dry Density :119.5p.c.f.

Moisture Content : 6.9 •1.

0.5 1.0

D1stc3n c e,

I -35 Ti II

ft.

Dry Density : 118.4 p. c. f.

Moisture Content : 11.9 •J.

1.5

0.5 1.0 1.5

D LS t c3 n c e, ft.

- E

2.0

2.0

ell -o c 0 u (!) ell

1-35 Till +

Dry Density :113.3 p.c.f. /

Moisture Content : 12.5 •J. .._~0 '":;~+ ":,

/+ /t

0 0.5 1.0

D1stc3nce, ft. 1.5 2.0

1-35 Till Dry Density = 120.7 p. c.f.

Moisture Content : 12.2 •J.

0 0.5 1.0

D1 stance, 1.5

ft. 2.0

Fig. 12. I-35 till.

(/)

"'0 c 0

111 "0 c 0 u ~ (/)

2.0

1.8

1.6

0

2.0

1,8

-= 0.8.

E o.6 -~ E oA

~ 0.2

.0

1- 3-5 Till

Dry Density :112.0 p.c. f. Moisture Content : 13'.4 °/e

0.5 1.0

D1 sta-nce, ·ft.

Greenfield Till - Gray Dry Density :106.6 p. c. f. Moisture Content : 8.0 °/o

0.5 1.0 1.5

D1 stance,- ft.

J.

2.0

2.0

l.l)

"'0 c 0 u Q; Cl)

-E Q;~

E r:

Cl)

-o c 0 u Q; (/)

--

0

2.0

1.8

1.6

1.4

0.2

0

Greenfield Ti 11- Gray

Dry Density : 111.7 p.c.f. /-!-Moisture Content : 9.2 °/o .._

"

+/ .,. ~/

.... ~ ./ 0~/>. +./

Q5 1~ 1~

D1stance, ft. 2:0

Greenfield Till - Gray · / Dry Density :108.7 p.c.f. .a.

Moi• '""' Content ' 9. 3 •1. /

"\ .... ~"'/+ Q" +/

+/ /

;/ 0.5 1.0 1.5

Dtstance, ft. 2.0

Fig. 13. I-35 till and Greenfi~ld till - gray.

2.0 C/)

~ 1.8

0 1.6 u Q)1.4 C/) = 1.2

f- 0.4

0.2

cJ) 2P '0 c 1.8 0 u 1.6 Q) C/)

0

0

Greenfield Till-Gray

Dry Density = 106.3 o.c.f.


0.5 1.0 1.5 2.0

D1stance, ft.

Greenfield Till- Brown

0.5 1.0 1.5 2;0

D1 stance,_ ft.

-V)

2.0

1,8

~ 1.6 c 0 1.4 v Q..r 1.2 V'l

-E

Greenfield Till- Brown

Dry Density : 118.8 p.c. f.

Moisture Content : 10.6. 0 /o

0 0.5 1.0 1.5

D 1 stance, f L

2 ·0 Greenfiek:l Till-Brown

1./J '0 c ~1.4 ~ 1.2 -. - 1.0 E ~ 0.8

Q..r

E

Dry Density :123.5 p. c. f.

Moisture Content : 12.2 °/a

0 0.5 1.0 1.5

D 1 stan c e, ft.

Fig. ·14. Greenfield till - gray and brown.

2.0

'., t

0.8 (!)

E o.G

0

1- 80 -Loess Dry Density :102.2 p.c.f. Moisture Content : 13.2 °/o +

o.5 1.0 1.5 2.0

Dtstance ft. 1

I- 80 Loess Dry Density : 105.0 p. c. f. . ~

Moisture Content : 13.7 °/o / .

/~

\9~ +/+ 0 "/ . ,_.._6 / ...

(!) 0.6 /

~:~v+ 0 0.5 1,0 . 1.5 2.0

·Dtstance, ft.

2.0

(/) 1.8 "0 . c 1.6 0 u 1,4 (J (/) 1.2

E 1.0

.. o.a (J

E I- 0.4

2.0

!ll 1.S \J g 1.6

u 1.4 ·~

- 1,2

E "0.8

(J

E -!-:" OA

0.2

0

0

1- 80 Loess Dry Density :103.8 p.c.f Moisture Content: 14.5 °/o

0.5 1.5 2.0

ft.

1- 80 Loess . .... . ~

Dry Density :102.8 p.c.f. '!I + / . . ·'~ / . Mo1sture Content ;:, 16.5 "/o ~0//""'/

. . "" t // ./:/ .

/;./ /

0.5 . 1.0 1.5 2.0

D 1st an c e ft . •

Fig. 15. I-80 loess.

N -..1

(/)

"'0 c 0 u QJ (/)

E

f- 0.4

0.2

(/)

"'0 c 0 u (!) (/)

0

0

l- 80 Loess Dry Density :106.1 p.c.f.


0,5 1.0 1.5

D1 stance, ft.

I- 80 ·Loess Dry Density : 107.4 p. c. f. Moisture Content : 12.6 °/o

0.5 1.0 . 1.5

D1 stance, ft.

2.0

2.0

2.0 If)

-o1.8 c 0 1.6

u Q;1.4

~ 1.2

-:: LO E ,0.8

<lJ E o.o

~0,4

2.0

(/) 1,8

"0 c 1.6 0 v1.4 Q; Ul1,2

1- 80 Loess Dry Density :104.6 p.~.t:


0 0.5 1.0 1.5

. D 1 s t a n c e~ ft.

1- 80 Loess Dry Density : 104.0 p. c. f.. Moisture Content: 14.2 °/o

0 . 0.5 1.0 1.5

Distance,· ft.

F~g. 16. r~so loess.

2.0

2.0

N CIJ

. r

2.0 1- 80 Loess 2.0 1- 80 Loess en -

, --u 1.8 Dry Density :104.8 p.c.f.

/ I() 1.8 /

c / 1J

0 1.6 Moisture Content: 15.0 °/o / c us /

u ,/""/. /t 0

Q) 1.4 u 14 en (!)'

1.2 /// + rn 1.2

,"""" >,.9., J./ - 1.0 . "" O/ ->,.9";/" \'1,'1, t E

.. ~0/ / ~(2 0; ,o_.../.... -t .

E o.s E _...//""// ~ OA I- / "" ....

Dry Density :118.4p.c.f.

Moisture C::ontent : 10.6 °/o

.... 02 , .... + / ....

0 0.5 1.0 1.5 2.0 0 0.5 1.0 1.5 2.0 '

01 stance, ft. Dtstance, ft.

en 1- 80 Loess 2.0

l:J c Dry Den~i ty : 112. 8 p. c. f.

r.f') 1.8

0 u

u Moisture Content: 13.9 O/o c 1 . .6 0

I- 80 ·Loess Dry Density : 109.4 p. c. f.


0; U14 en + (!)'

.,.-/ <f1 - 1.2

E ·~ -= I 0 ... E . ., ... ~

\9~ ._Q,8

1 '\0 "T (!)

"/-""" . EO-~ . ~

/""" 1- 0.4 ~+ ... . 0.2

0 0.5 1.0 1.5 2.0 0

Distance, ft. . 0.5 1.0 1.5 2.0

D 1st an c e, ft.


2.0 I - 80 Loess 2.0 I- 80 Loess !I)

1.8 Density u Dry :117.6 p.c. f. If) 1.8 c Moisture Content : 9.9 .,. -g 1.6 0 1.6 /+ u

1.4 0 ~ /+ u 1.-4 C/)

~ 1. 2 /+ !I) 1.2

E 1,0 + --1.0 ,~y -

.... 0;8 \~~+ ~ Q8 ~

E O.G -- /

f- 0.4 /+ ~OA

0,2 ~,/~

Dry Density :117.8 B. 120.2 p.c.f.

Moisture Content : 11.4 & 10.8 •J.

_0 0.5 1.0 1.5 2.0 0 0,5 1.0 1.5

---o 1 stance, ft. D1stance 1 ft.

2.0 I- 80 Loess 1.8 Dry Density :103.8 p.c. f.

1, 6 Moisture Content: 13.2 •t. !I)

1.4 "0 c 0 1,2 u ~ 1.0 ill -- 0.8 E ~ o.cs E 0.4 ~

0.2

0 0,5 1.0 1.5 2.0

Distance, ft.


2.0

w 0

31

Table 2. Summary of field test results (no correction for delay).

Measured Measured moisture Seismic dry

Field Velocity content Compactive density density test (fps) Soil (%) effort (pcf) (pcf)

1 1980 I-3S 8oS LS 122.4a 129.S

2 2366 I-35 8.9 L9 123.6a 129.0

3 1187 I-3S 8.6 0.4 114a 12So4

4 1204 I-3S 8.1 0.7 11S8 127.2

s 1163 I-35 s.s o.s 1148 130~2

'

6 1910 I-35 6.7 2.1 119a 124.2

7 3040 I-35 6.9 4.6 128.4a 130.1

8 1100 I-3S 8.6 0.5 usa 117.4

9 1165 I-35 6.9 1.1 113a 119 0 5

10 1S70 I-3S 12.5 < 1 <;. 119a 113.3

11 1S70 I-3S 1L9 < 1 < 121 a ll8o4

12 2470 I-3S 12.2 s 12la 120.7 /

13 1S90 I-35 13.4 < 1 < 118a ll2o0

14 1094 Grfd gr 10.6 < 1 < 108a 11L7

lS 1094. Grfd gr 8.0 < 1 < lOS a 106.6

16 917 Grfd gr 9.3 < 1 < 108a 108.7

17 1370 Grfd gr lOuS < 1 < 108a 106u3

18 2630 Grfd br 10 u 6 l.S 104a ll8u8

19 1510 Grfd br lO.S < 1 < 101 a 111.5

< 102a I .

20 1920 Grfd br 12.2 < 1 123.5

21 1180 I-80 13.2 < 1 < 102a 102.2

22 2200 I-80 14.5 < 1 < lOSa 103.8

23 1160 I-80 13.7 < 1 < 104a 10S.O

-------------- ~~-------

32

Table 2. Cont.

Measured Measured moisture Seismic dry

Field Velocity content Compactive density density test (fps) Soil (%) effort (pcf) (pcf)

24 1150 I-80 16.5 (3 .2) (111) a 102.8

25 1160 I-80 12.6 < 1 < 103a 106.1

' < l03a 26 1400 I-80' 13.4 < 1 104.6

27 1110 I-80 12.6 < 1 < 103a 107.4

28 1430 I-80 14.2 (5) (114)a 104.0

29 1220 I-80 15.0 (4) (111) a 104.8

'30 1380 I-80 10.6 < 1 < lOOb 118.4

31 1710 I-80 13.9 (5) (116)b 112.8

32 1410 I-80 15.6 (3) (112) b 109.4

33 1300 i-80 9.9 < 1 < 99a 117.6

3.4 1640 I-80 10.8 1 lOOa 117.8

35 1120 I-80 13.2 < 1 < 103a 103.8

aSeismic density test taken up to several days following field com-paction.

bs . . el.Sml.C density test taken immediately following field compaction.

..

+'

u 0

QJ

>

""-:

u a.

>. +' (/)

c ~

0

>. L

0

<4000

. ----------------------------------------------------------------------------,

6 8 10 12 14 16 18 .u· 22 .

& 8 10 12 14 1e> 18 20 22

Mo1sture Content, 0 /o

33

. (_

112 116 120 124 128

Dry Dens1ty, p.c.f.

1-35 Till

AA~HO Standard 0 0

AASHO "-'1odi f ~ d +--+

Fig. 19. I-35 till •

·+

. \.._;

4000

3500

. 3000 (/)

a: -2500

>.· +"

u 0 2000

Q)

>

34

500 6 8 10 12 14 16 18 20 22 100 104 108 112 116

Dry Dens1ty , p,c. f. 126

124

122

120 ~ L! 118 Greenfield T11l - Brown a. I

~

>. AASHO Standard () 0

~ 114 AASHO Mod111ed (/) -t--+ c Q)

0 110

>. 108 '-·o

Fig. 20. Greenfield till - brown.

. 120 124

"+-; u ci.

({)· c Q;

0

>, L

0

6 B 10 12 14 16 18 20 22

Mo1 sture Content, 0 /o

35

Greenfield Till- Gray

AASHO Standard o o

AASHO Modified +--+

I

Fig. 21. Greenfield till - gray.

+

I

I.

I

..

""'-: u 0.

~ ........ &/)

c ~

0

>. L

0

96

36

I I ..

100

Dry 104 108 112

Dens1ty, · p.c.f.

1-80 Loess

AASHO Standard

AASHO Modif1e-d

Fig. 22. . I-80 loess.

o:---o'

+-.-+

116

.. 37

CONCLUSIONS

1. Seismic velocity versus moisture content curves for standard and

modified Proctor compacted laboratory soil specimens are similar in shape

to dry density versus moisture content curves, but peak with about 1.2 ±

0.9% lower moisture content, the ±entry indicating one standard devia

tion on the mean.

2. The seismic velocity versus moisture content curves are very sensi

tive to overcompaction, i.e., when compaction proceeds at too high a

moisture content, shearing the soil.and dispersing the clay. The method

therefore does not appear to be usable for measurement of density when

the moisture content greatly exceeds the optimum for compaction.

3. Field velocities obtained in this study in all cases are too low

for a reliable estimation of field density from laboratory seismic data.

Subsequent laboratory tests indicated that the reason is a gradual reduc

tion in velocity upon aging, apparently because of gradual absorption of

pore water into the expandable interlayer region of the clay. Seismic

tests therefore should be conducted immediately after compaction or the

results become meaningless.

r -------------------------------------.

38

•

• REFERENCES

•

1. Dobrin, Milton B., Introduction to Geophysical Prospecting, 2nd ed. New York, N.Y., McGraw-Hill Book Co., Inc. 1960.

2. Barkan, D. D., Dynamics of Bases and Foundations, New York, N.Y., McGraw-Hill Book Co., Inc. 1962.

3. Jones, R. and Whiffin, A. C., A Survey of Dynamic Methods of Testing Roads and Runways, Highway Research Board Bulletin 277: 1-7. 1960.

4. Goetz, W. H., "Sonic Testing of Bituminous Mixtures," Association of Asphalt Paving Technologists Proceedings 24: 332-355. 1955.

5. Whitehurst, E. A., Evaluation of Concrete Properties from Sonic Tests, Am. Ceram. Inst./Iowa State University Press. 1966. 94 pp~

6o Whitehurst, E. A., "Pulse Velocity Techniques and Equipment for Test-ing Concrete," Highway Research Board Proceedings 1954: 226-242. 1954.

7. Leslie, J. R., "Pulse Techniques Applied to Dynamic Testing," American Society for Testing Materials Proceedings 50: 1314-1323. 1950.

8. Manke, P. G. and Gallaway, B. M., "Pulse Velocities in Flexible Pavement Construction Materials," Highway Research Record 131: 128-153. 1966.

9. Moore, R. W., "Summary of Restillts of Current Seismic Wave Velocity Versus D'ensity Tests Performed for Sub-Task Group on Nondestructive Testing-Quality Control," Unpublished: mimeographed paper. , Washington, D.C., Office of Research and Development Materials Research Division. Bureau of Public Roads. US Department of Commerce. ca. 1965.

10. Illinois Institute of Technology Research Institute. (Part G. Seismic Tests). Unpublished mimeographed paper. Chicago, Illinois, author. 1966.

11. American Society for Testing Materials. 1965 Book of ASTM Standards. Part 11. Philadelphia, Pa., author. 1965.

12. Seed, H. and Chan, C. K., "Structure and Strength Characteristics of Compacted Clays," ASCE Jour. 85:5M5:Pt. 1:1:87-120. 1959.

JFW/ljo

seismic wave velocity as a means of in-place density...

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