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Distribution authorized to U.S. Gov't. agenciesand their contractors; Critical Technology; AUG1970. Other requests shall be referred to ArmyEngineer Waterways Experiment Station,Vicksburg, MS 39181. This document containsexport-controlled technical data.

usaewes ltr, 27 jul 1971

©I

TECHNICAL REPORT NO. 3-783

AN ANALYTICAL MODEL FOR PREDICTING CROSS-COUNTRY VEHICLE PERFORMANCE

APPENDIX R SOIL-VEHICLE RELATIONS ON SOFT CLAY SOILS (SURFACE COMPOSITION)

OCT 21 1970

August 1970

ky AdvanMd RMMfdi ^^•wcy

Dirtctorat« of P»«lopw«t «MI Eofli"^«"»» W. S. An^r

StniM NfMqr U. S. AfWT M*»fH ONiKM bf u/sArmr Eiigi-«rW^r«iri^«l»A~<* Statt

TM docwMirt is sabtid Is spscW ôrt a^Mm «„ be msde ort» wH* prior ipuwil ol U. $. «m»

3?'8/

W|

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The findin«. in Ai. r^)ort ore not to be construed o« on oHieiol Deportment of the Army position unless so designated

by other authorized documents.

r

TECHNICAL REPORT NO. 3-783

AN ANALYTICAL MODEL FOR PREDICTING CROSS-COUNTRY VEHICLE PERFORMANCE

APPENDIX F: SOIL-VEHICLE RELATIONS ON SOFT CLAY SOILS (SURFACE COMPOSITION)

C. A Blackmon

1970

Spenofrt by Advanced RcsMrch Proitcb Agency

Directorate of Dovolopmonl «id Enginooring, U. S. Army Materiol Comnwiid

senkt «cency U. S. Army Materiol Command

Proiact Nos. |.T-0^2II2.A-I3I and |.T-0-62l03-A-046^)2

OonducM by U. S. Army Enginoor Waterways Exporimonl Station, Vicksburg, MitsisMppi

•■MT-M»e «ICBMUM. ma*.

This document is subject to may be made only »ith prior

totmipi approval of U. S. «nay Engineer Watonrays EipcrtoMiil Station.

THE C0I3TEHTS OF THIS REPORT ARE HOT TO BE

USED FOR ADVERTISIIIG,' RJELICATIOII, OR

PROMOTIONAL RJRPOSES. CITATIOH OF TRADE

NAMES DOES NOT CONSTITUTE All OFFICIAL EN-

DORSEMENT OR APPROVAL OF THE USE OF SUCH

COMMERCIAL PRODUCTS.

iii

arcfj r-'-, Study (.'"-ino,1 sponsorea

Jiii), rwr.r-- Arrr.;.-

nse acen. •vroaa Tr.i£'3i3r. Df Pro;'-

c features of the physi»

~r;ur.i cotitÄCt vehlyles

e'■orolect vac that the

7* ön 131 T*I

'C ■Klrr'riii Or

- r» ^ '" Q ^ c - ■p

~j-' ■v»0'^',_'^>^ f Develc

EnvirorHoeutai con*

November 19-5;

TisioE 'of the MBRS Branch of the WES,

} Volvuiie I: Lateral Obstacles

Volume II: Longitudinal Obstacles

C. Vehicle Performance in Vertical Obstacles (Surface SeOttetry)

D. Perfoi-nance of A^phicicus Vehicles in the Wftter.|*»d Inter- ^

face (Hydrologie Geometry)

■E. Quantification of the Screening Effects of Vegetation on

Driver's Vision ar.i Vehicle Speed

F. Soil-Vehicle Relations on Soft Clay Soils (Surface

Composition)

G. Application of Analytical Model to Uni-: States anu Thailan.

Terrains

The study was conductea by personnel of the Mobility an. Environmen-

tal .(M&E) Division, under the general supervision of Mr. V.T, J. Turnbull,

Technical Assistant for Soils and Engineering (retire^; ^- ■••• S« Shockley

and Mr. S. J. Knight, Chief and Assistant Chief, respectively, Ê Divi-

sion; Mr. A. 'A. Rula, Chief, Vehicle Studies Branch; Mr, W. E. Grabau,

Chief, Terrain Analysis Branch; and Mr. J. K. Stcli, Chief, Ccstacê-

Vehicle Studies Section. Special ack-novledgnient is made to Mr. E. 3. Rush,

Chief, Soil-Vehicle Studies Section, and Mr, ". R. Murphy, engineer, /erh-

ole Dynairäcs Section, who provided guidance for portions of the analysis.

The tests reported herein were supervised by Vbt, B. 0. Stinson. Major

assistance in the preparation of plates and tableo was provided by M*i J. I

Lee. This report was written by ^f. C. A. Blaokmon.

Directors of VBB during this study and the pTf ^ration of this re-

port were COL Alex G. Sutton, Jr., CS, COL John R. Oswalt, Jr., CE,

COL Levi A. Brown, CE, and COL Emest D. Peixotto, CE. Technical

Directors were Messrs. J. B. Tiffany and F. R. Brown.

vx

co:rrE:n:s 1 (»

Page

CONVÎON -AC"-^- BRITISH TO '-ZTHIC UIIITS OF ÊASURBMERC 'ix w Wö . _. , - ^ ...

S'J?"J\?Y " * X1

PART i: rrrPOBUcnio". F1

BÄökffround \ . . F1 ^ "■" -pi Pirnose ar.d Scope. ,

PAF.T II: TEE" PP.OGFAV .: F3

Location and description of Test Areas •. • F3 Vehicles lêd v, Fö

Tests Corducted ' • F9 Test Procedures and PerfoiT.ance Data Obtained > > F9 Soil Tata Obtained | Fll Other Tata Obtained ' F11

PAFT III: AliAIYSIS 0? DATA N F1^

Basis of Analysis ' '• Acceleration Relations • Deceleration Relations ,. . . Prediction of Vehicle Performance F19 Comparison of "easured and Predicted Average Speeds F29

PAF.T TZ: C0::CLUSI0!S Arn) REC0N3>!ENDATI0rro ' F32

F32 . . . ........... * -t1-

Conclusions. . . Recorrr.er.iatior.s,

LITERATURE CIT:

TABLES F1-F10

PLATFS F1-F10

*

vii

;

FlU Fl6

FS2*

r

•^

British unites of .T.eas'oreîen'C us^d in this report

Units as fellows:

Multiply - ' 27

^ P ^ - r - ' o ^ r c

inches

feet

miles (U. S. statute)

pounds

short tens (200C lb)

pounds per scroare ir.c:

leet per second

ules Tjer hour

2î-

1.609344

0.-53592: or7 tRe.

0,070307

0.3048

1.609344

^l^ C u 8.1 n

CG nf: i -ezt . V s

rr.e ze V 3

•CXXC^T^ Tiers

kilograma

hilcsrans "cer zc'SQ/n 2 e nt ir.ê 1J e r

Bieters per s'eccr.d

kilometers ~er hear.

IX

V- / X

SUMMARY

Sixty-six acceleration-:eceleratior. tests were conducted with three wheel-! an: two tracked vehicles at five sites in Thailand. The principal conclusion fro« these tests was that vehicle deceleration in soft clay- soils can be correlated with soil strength expressed as the average C- to 6«in. cone inaex. The analysis indicated that acceleration increased with an increase in soil strength, "cut no definitive correlation could be established. Semieiffiirical ani etnpivical relations were used in a first- .-eneration analytical model to predict average speed over the test courses. Conmarisona Of measured ana predicted speeds led to recommendations for specific additional studies to improve the reliability of the OTS"analyti-

cal model.

XI

AN AIIHLYTIGAL MODEL FOR PREDICTING

CROSS-COUHTRY VEHICLE PSRFORMAHCS >.

APPEIJDIX F: SOIL-VEHICLE REIATIOIB ON SOFT CIA'f SOILS (SURFACE COI-IPOSITION)

PART I: II?TRODUCmo:

3ackgrc-jnd

1. The nain text of this report describes the development of an ana-

lytical model for predicting the cross-country perfcmance of a vehicle.

The ripdel was based on an energy concept within the framework of classical

mechanics that requires cause-and-effect relations be established between

discrete terrain factors and vehicle response. The terrain factors con-

sidered in the analytical model are (a) surface geometry, (b) surface com-

position, (c) vegetation, and (d) hydrblogic geometry. This appendix deals

with limited aspects of the surface composition factor—the effects of soil

strength pn the acceleration and deceleration of the vehicle.

2. Previous and concurrent studies in the field and laboratory have

yielded empirical and semiempirical correlations of soil strength and ve-

hicle performance in terms of minimum strength negotiable, motion resist-

ance, and drawbar pull. A method of predicting vehicle performance while

accelerating and decelerating has been presented in a recent report; how-

ever, no actual vehicle performance tests were included in that study.

Purpose and Scope . .. ■ #

3. This appendix describes acceleration-deceleration tests con-

ducted by the U. S. Army Engineer Waterways Experiment Station (WES) in

Thailand during the period l£-30 October 1965. The general purpose of

these tests was to obtain data relating characteristics of soft clay soil

to vehicle performance in terms suitable forûse in developing that portion

of the analytica] model for predicting cross-country performance. The spe-

cific purpose was to determine if vehicle performance in terms of

Fl

acceleration and deceleration could be related to soil strength. An addi-

tional purpose of this report was to compare the average speeds predicted

by the '«"ES analytical node! using both empirical and semiempirical corre-

lations of soil strength and vehicle performance with the average speeds

measured in field tests. U. Sixty-si^ tests were conducted with three wheeled and two tracked

vehicles at five 4tes in Thailand. Surface composition of all sites in

terr-.s of the Unified Soil Classification System (USCS) was a fat clay (CH);

the average soil strengths in the 0- to 6-in.* layer ranged from l6 to 71

cone index.

* A table of factors for converting British units of measurement to metric

■„units is presented on page ix.

F2

^ ,, . ...

PART II: TEST PROGRAM

Location and Description of Test Areas

_ ' - ' — . | I 5. The tests reported herein were conducted at three getfieâl loca-

Jtions in Thailand: Pran 3uri, Phet 3uri, and Sariut Prakan (ilg. Tl).

Descriptions of the test site« at the tir.e the tests were conducted are

given in the following paragraphs.

; ' -.'. ' J. }• r c - :■

is \ -v I

SCH^t ^MILtS

/

Fig. Fl. Vicinity map; Samut Prakan, Phet Buri, and Pran Buri test sites /'

F3

J > V v^

/ /

Fig. F2. Location of Pran Buri test site

"4 W ^\

#£.-_-

ytu: v «»-t5

Pran Buri 6. Test site UV-S-3 was located about lU miles south of Pran Buri

near the village of Ha Wan Priang (fig. F2) in a gras^-covered, low-lying

area dissected by drainage canals. The site was approximately 300 ft

long and 2X ft wide and very nearly level (less than 0.5 percent slope).

As stated previously, f* soil at the site (and also at the four other

test sites) was classified as CH according to the USCS. The average cone

index of the 0- to 6-in. layer ranged from 5^ to 71. The site was free

of -urface irregularities (fig. F3a).

y

FU

■ --1 -1

/

/

/ a. Grass-covered s'orface / at site UV-S-3

b. k» tc 6-in.-deep s1arface vater at site

c. Srall-scale surface irregularities at site HPDC-X^

Fig. ?3. Surface cpnditicns. at three test site:

F5

•

Phet Buri

7. Test site MRDC-X,- was located about 11 miles southeast of Phet

Buri (fig. F4) in a low-lying area containing no vegetation. The site

was apprcxinately 300 ft long and 200 ft wide and very nearly level (less

than 0.5 percent slope). The average cone index of the 0- to 6-in. layer

ranged from Ul to 6k. The site was free of surface irregularites.

V

SCmt .X MiL£5

Fig. FU. Location of Phet Buri test site

F6

'■■"■■■•-.-

Samut Prakan

8. Three test sites were located in the Samut Prakan test area

(fig. F5). Test site MRDC-Xp was about 6 miles southeast of Samut Prakan;

test sites MRDC-X. and MRDC-X/- were near the village of Tambon Khlong Dan.

All were in low-lying areas containing no vegetation. Each was approxi-

mately 300 ft long and 100 ft wide. They were oriented so that the slope

of each test lane was less than 1.0 percent. At the time of testing, site

MRDC-X^ was covered with 3 to 6 in. of water, site MRDC-Xg with U to 8 in.

of water (fig. F3b), and site MRDC-X^ was very wet but nearly free of sur-

face water. The average cone index of the 0- to 6-in. layer ranged from

29 to k3 at site MRDC-Xp, from 27 to h2 at site MRDC-X^, and from l6 to 20

at site MRDC-Xg. The small-scale surface irregularities that were present

at all the sites in the Samut Prakan area were judged insignificant from

the standpoint of vehicle performance (fig. F3c).

■ TCtt SlTCS

5C*L€ S MÊS

Fig. F5. Location of Samut Prakan test sites

F7

mv.m.mmp

Vehicles Used

9. -rnree wheeled vehicles-the 1-5151 lA-ton utility truck, the M37

3/U.ton cargo trucV-, and the M35A1 2-l/2-ton cargo truck-and two tracked

vehicles-the K9C amphibious cargo carrier and the M113 armored personnel

Carrier-were used in these tests (fig. F6). Pertinent physical

_^*^*iV

i^î iv

t. !-!151 l/h '.or. utility true?.

M35A1 2«-l/2-ton oarsd truck

b. K37 3A-ton cargo truck

M29C amphibious cargo carrier e. M113 armored personnel carrier

«1- v^ Mh«»lftd «^d tracked vehicles used in test program

F8

■■>

characteristics of the vehicles are given ir^ table FlJ

10. All test vehicles were equipped with faiply elaborate measuring

and recording systems. This instrurentation is di^cussefi in detail in

reference 2.

Tjssts Conducted

oi-J_^

_;. w:._u:.

ll. The acceleration-deceleratior. tests cor.ii

considered as being of two types on the basic of th«

deceleration in each test was acGor.plishei. vrr.er. z':

to a stop by free-rolling, i.e. with the c-lutch disengaged, the t-=st was

;oUiy were

the

.•ehi^le was brought

considered to HeanaXjcele ration-rolling test ( identified by the le'ü-er R

followiQg^the test rrinber); when the vehicle was brought tc a step by ap-

plication of the brakes, the test was considered to be an acceleraticn-,

braking test (identified by the letter B following the test nurr.ber).

Tests employing both methods of deceleration were conducted with each ve-

hicle, although not at each site. The following tabulation shows the

number and type of tests conducted with each vehicle at each test site.

Vehicle and Type of Test M151 R_ B R_ 3

125 |

Al B

M2<? H ~3

Ml 1 "^' Tests Test Site pk 3 H_ 3_

l+V-S-3 2 1 3 3 2 2 "I ^5 2 13 5

MRDC-X10 3 2 3 3 2 2 2 1 2 Q 12 6

MRDC-JC 3 2 3 0 2 0 0 0 0 8 2

MRDC-X^ 3 2 d 0 0 0 3 2 Q ,3 S It

MRDC-Xg 0 0 0 0 0 0 3 c rt J *3 o

Total 11 11 5 I 10 1* M. 22

f

S'

Test Procedures and Performance Data Obtained

12. The-,vehicle was positioned at the beginning of the 300-ft-long

test lane and the driver was instructed to accelerate the vehicle as

quickly as possible to a point that would allow ample rcor/fcr deceleratic

without overrunning the test course, and then tc disengagej the clutch (in

F9

the acceleration-rolling tests) and allow the vehicle to roll to a stop or

to apply the brakes (in the; acceleration-braking tests) and bring the ve-

hicle to a stop. The wheeled vehicles and the M2^C, all having manual

transmissions, were usually started in second gears low range, and shifted

to third gear, low range. The M113, the only vehicle with automatic trans-

mission in the test program, was operated in gear range 3-^ in six tests

and in gear range 1-2 in one test. Poles were placed at 50-ft intervals

along the edge of 'she test lane to serve as reference points and to assist

the driver in following a straight-line course ifig. F7). Since it was

Fig. F7. Site MRDC-XIQ. Poles at edge of test lane assisted driver in following course and served as

reference points

believed that variation in driving ability, for instance in the time re-

quired to effect a gear change, might affect the test results, the same

driver was used throughout the test program.

13. By means of electronic instrumentation installed on the test »

vehicles, continuous measurements of time, distance traveled, drive-shaft

revolutions, and wheel or track rotational speed were made and recorded

en cscillograms. In addition, for some tests drive-line torque and longi-

tudinal acceleration were measured and recorded. A surveyor's chain was

used to validate total distance traveled and a stopwatch was used to obtain

a check on total time. Appropriate data from the tests are summarized in

table ?2. Voluminous data were obtained in reducing the oscillograms to a

-ore cenvenient-to-use form. For example, distance traveled, vehicle

F10

speed, wheel or track speed, percent wheel or track slip, and average

acceleration or deceleration of the vehicle were determined and tabulated

for each second of each test. In the interests of economy, these data are

not reproduced in this appendix but are filed at WES for future reference.

Soil Data Obtained

Soil samples

lii. Samples for classification of the soil according to theJJSCS

were obtained from the 0- to 6-in. and 6- to 12-in. soil layers from each

test site. A summary of the laboratory data is included in table F3.

Grain-size distribution curves are shewn in figs. F8 and F9«

Cone index ^,

15. Cone indexes were measured at the surface and at depths of 1, 2,

3> ^J 5> 6, 9, and 12 in. at 6-ft intervals along each side, of the test

lane prior to testing. In some tests, the vehicle straddled ^me of the

ruts of a preceding test and the previously collectedsoil data vere

deemed adequate. Following each test, the portion of the lane in which

the vehicle was accelerating and the portion in which the vehicle was de-

celerating were determined. A summary of the cone index data is given in

table Fh. . '

Other Data Obtained

16. Other data obtained Included photographs, miscrllaneous measure-

ments, notes, and observations. Data not included in this appendix are

filed at WES for future reference.

■Fll

\

\

■■'■•■ -■ ■• ■ •'■■" ■•- ■ "

r^- . MS - HMK-I—T^8"*" a i .t—c "—l-a^tJ—i 1

LEGEMP

___^__ 0- TO «-IN. LAYER tmm-mmm •• TO 1t-IN. LAVtH

fi* F8. Grain-size distribution of soils at Pran Buri g* (W-S-3) and Phet Buri (MRDC-X10) test sites

F12

-? •■ M r i T ?>.' ? t v'fu? ?-ryT?

::: ::::'

u i i'wuc vtn o«fMNc M MO« u s sfwc*» vtt MuMim / •••two* • 4i i '■» i (» ■>»»«« in i«» » ic «o »o ^«ygîy /— —r-t-r-i-r-r-TT T-r-rT I n-rr-r-r r-T—r I »î jr

I« S '

I"

MR0C-X4

-T-T^T"T-r

14 I 1 MRDC-X,

GUM yn ««iwtf*m

LEOENp

0- TO ••IM. UAVCH l •• TO «-IN. LAVCN

Fig. F9. Grain-size distribution of soils at 2' test sites

Pral

7 /" * . ' .,/■

■ 'PAKT III: ANALYSIS OF DATA

17. The iata collected In this test program were analyzed tc det€.--

Sdm it acceleration and deceleration of vehicles coiad be related to soil

strength and to e-;aluate the accuracy of current prediction techniques for

vehicles accelerating and decelerating over short distances.

, • - Basis of Analysis

18. Acceleration is, by definition, the time rate of change of ve-

locity. Matheratically, this nay be expressed by the equation

where ' - , V , ?« = speed at the beginning and end, respectively,

1 cf an incrc-nent of tine, fps

% * tine increnent, sec

a = acceleration, ft/sec

When the spe^d at the end if the increnent (Vg) is less than the speed at

the beginning of the increnent (V^, the acceleration is negative and is

temed deceleratiab (-a)/' Equation 1 in various forms is used throughout

the analysis; other special considerations and equations peculiar to a

ârticular part cf the analysis are discussed as they are introduced. ■ - ■ C * ' ' ' ' J

Acceleration Relations v

la. The acceleration a îven vehicle can achieve depends on that

vehicle's characteristics (weight, engine performance, transmission effi-

ciency, etc.), the skill of the driver ("in steering, feeding fuel to the

enginl', shifting ge?.rs, etc.), and the conditiqa of the surface on which

the vehicle operates. In these: tests, changes in the characteristics of a

given vehicle that occurred between tests or within a test were not con-

sidered to be significant, and driver effects were minimized (but not

eliiinated) by using the, sane driver in all tests. Thus, even though the

tests lacked consistency (distance or time in which acceleration occurred

?\h

7

was not the same in ail tests) and no attempt was made to attain a maximum

ve-lcity because of the prohibitive length cf the test course that would

have been required, it was felt that some quantitative estimate of the

effect of soil strength on acceleration could be made. Fig. F10 shows the

a kl kl a M

/

Fig. F10. 5x)eed-time curve for test 269 R- (Data from Which this ,/ plot was constructed are given in table FlO) j

\ ' / speed-time curve for a typical test. It is to be noted that accel/raticn

(slope of the curve) was constantly changing; dashed portions of'the curve

represent the abrupt change when the gears were shiftea. Several plots of

acceleration and/or velocity versus soil strength were made as follows:

/ Parameter Soil Strength

Maximum acceleration (usually occurred Average 0- to 6-in. cone.index of during first 1-sec time increment of the ccrresponaxng portion of the

test) test lane

Average acceleration until time clutch êrage 0- to 6-in. cone index of -e,,. , -mo r.rrT«<a.c:Tinnr5-5ne portion of th was disengaged

Average acceleration during first 5 sec

Average velocity for first 100 ft

the corresponding portion of the test lane

Average 0- tc 6-in. cone index cf the corresponding portion Of the test lane

Average 0- to 6-in. cone index of the corresponding portion of the

~~ test lane s

F15

/

20. Ali these plots showed a fairly general effect of cone index on

acceleration. The plots that appeared nost iufornative were those of maxi-

ma aêlerati-r. versus the average 0- to 6-in. cone index for that portion

rthe test lane where the maxinun acceleration occurred. These plots are

discussed in the following paragraphs.

Wheeled vehicles ,

21. Plots of naximtcr. acceleration versus the average 0- to 6-in.

cone index are shown in plate PI« Results fron tests conducted on bare

surfaces are indicated by open symbols; results from tests on grass-

covered surfaces are indicated by closed synbols. While the limited range

of strengths in each surface-cover grcup and the obvious scatter of data

for M151 tests (fig. a, plate Fl) seem to preclude drawing a definitive

curve through the data points, scne trends are evident. The increase in

acceleration with an increase in soil strength for the 1-37 and r'85Al tests

( figs, b and c, plate ?l) is impressive, and it nay be noted, especially

in fig. b, that the closed synbcls appear as a logical extension of the

open syr.bcl?, suggesting tc some extent that the soil strength has a

greater influence upon acceleration than does the surface cover.

Tracked vehicles

22. Plots cf naxirr.un acceleration versus the average 0- to 6-in.

cone index are shown in plate ?2 for the two tracked vehicles. Again,

while no curves are presented, it nay be seen that there is a trend toward

an increase in acceleration with an increase in soil strenHh.

r

Deceleration Relaticns "

23. The deceleration of a vehicle depends upon that vehicle's char-

acteristics (weight, traction element contact area, internal resistance

when' rolling, and how quickly the wheels or tracks can be locked when ad-

vantageous for braking), the skill of the driver (in steering, application

of brakes, etc.), and the condition of the surface on which the vehicle

:rerates. In the rolling tests, changes in the characteristics of a given

vehicle between tests were net considered to be significant, and the driver

effects were minimize I (but not eliminated) by using the same driver in all

Fl6

/

/

'^«^-'»•Sri.:--.-*. I „M ——1 IM ■—,... mm■ H.M ■.- - ■'•- — --..—...^ ■ >nw,,wm ■—■— i Nin i ■ i i i ■■■ ■ ■"mnmiiMimtmmm

tests. In the braking tests changes in the vehicle's characteristics were

deemed significant. For example, it was not always possible to lock the

brakes, particularly wher. the brake drums became wet (fig. ?ll). Addition-

ally, during the braking tests.at some of the grass-covered sites, the

grass sheared irregularly (fig. F12). It is believed that these factors

were, in part, responsible for the highly variable results of the braking

tests. Since an investigation of these factors was not within the scope

of this program, only the tests in which deceleration was accomplished by

disengaging the power train and allowing the vehicle to roll freely to a

stop are considered in this part of the analysis.

2h, For most of the tests considered, the deceleration for each

1-sec time interval from the tijne the power train was disengaged until the

vehicle stopped rolling was fairly constant (see fig. FIO). In a few cases

(one M151 test, six M37 tests, and one M113 test) malfunction of the dis-

tance play-out line prevented a second-by-second determination for the en-

tire period of deceleration; therefore, the value of deceleration expressed

as -a/g given in table F2 was determined over less than the full period

of deceleration. .. >

Wheeled vehicles

25, Plots of average deceleration versus the average 0- to 6-in.

cone index are shown in plate F3 for the three wheeled vehicles tested.

The curves drawn in figs, a, b, and c, plate F3, represent the lines of

visual best fit. The minimum soil strength required for one pass (VCL^

is shown for each vehicle. It was computed by a semiempirical method now

being developed at WES.* It may be noted that the deceleration for the

M151 is higher than that for the other two vehicles at approximately the

same soil strength. This may be explained in part by realizing that decel-

eration represents the result of all forces resisting motion of the vehicle,

including the surface condition, and it would be expected that water or a

* Work in progress and curves relating a computed mobility index to the vehicle cone index required for one pass and fifty passes of a vehicle on level soil are described in "Quarterly Progress Report on Waterways Ex- periment Station Research and Development Projects" for the first quarter of 1969.

F17

.'■'

Fig. Fll. Splashing water wet the brakes at site MRDC-Xg

Fig. ?12. Ilcte grass shear during deceleration by braking at site Uy-S-3

?l8

slushy surface condition (such as that encountered in these tests) would

have a greater retarding effect, percentagewise, on the smaller and lighter

M151 than on the heavier and larger M37 and K35A1. For this reason, in

fig. d, plate F3 (where the deceleration values for all three wheeled ve-

hicles were plotted against soil strength expressed as cone index points

above VCL. to establish a single relation), the location of the curve was

influenced to a greater extent by the M37 and M35A1 data points than by

the M151 data points. The location and curvature of the line in fig, d are

admittedly arbitrary and somewhat provisory. The extrapolation as indi-

cated by the dashed line is based on results of other studies in the field

and laboratory that indicate that the towed force-soil strength relation

becomes asymptotic at a force/weight ratio of approximately 0.30. Data

in this region are extremely scarce, and it is emphasized that the relation

expressed by the curve in fig. d, plate F3, may be changed when additional

data become available. Nevertheless, the curve in fig. d does define a re-

lation between deceleration and soil strength that appears reasonable.

Tracked vehicles

26, Plots of deceleration versus soil strength expressed as the

average 0- to 6-in. cone index are shown in figs, a and b, plate Fh, for

the M29C and the M113, respectively. The summary plot (fig. c) indicates

that the data correlate quite well when soil strength is expressed as cone

index points above VCI,. The curves drawn through the data points repre-

sent lines of visual best fit. The extrapolation of the curve on the sum-

mary plot follows the same reasoning as that for the summary plot (fig. d,,

plate F3) given in the preceding paragraph. Examination of the data pre-

sented in plate Fh indicates that while the decrease in deceleration with

an increase in soil strength is very small, the correlation is good and

the curves adequately define the relation of deceleration and soil strength

within the limits encountered in this program.

Prediction of Vehicle Performance \

27. Although the tests were not typical of normal vehicle operation,

they did furnish some data in terms of average speed of real vehicles over

F19

sections (albeit short) of natural terrain that could be used for compari-

son with ayerage speeds predicted by current modeling techniques, and, in

a sense, serve tc validate the relations established in this and concurrent

test programs. To this end, predictions were made of the average speed and

compared with the insured average speed in 52 tests. Of the 66 tests,

data for ih tests were incomplete and are not used in this portion of the

analysis. The prediction techniques are described and illustrated by ex-

'ample in the following paragraphs. i

Pavement-vehicle relations , ,

28. The WES analytical model for predicting cross-country perform-

ance of military vehicles begins with a basic relation peculiar to each

vehicle that expresses the maximum tractive force that can be developed at

any speed on a firm, level surface (e.g. pavement). The relation for a

particular vehicle may be obtained empirically by drawbar pull-speed^ and

motion resistance-speed tests on a firm, level surface or my be confuted

from engine performance data, taking into account propulsion system JLosses.

The paveirient data used in these predictions are shown graphically in plate

F5 and in tabular form in table F5. The data sources are indicated in

table-F5.

Soil-vehicle relations

?9. The next step in the WES analytical model is to establish the

effects of soil strength by using the maximum drawbar pull and motion re-

sistance values for the vehicle and particular soil condition. Ideally,

these values would be determined by actual field tests on the same soil

condition for which the speed prediction is being made. Since this is not

always practicable, a part of the overall Mobility Environmental Research

Study (MERS) program was concerned with developing methods of predicting

maximum drawbar pull and motion resistance and with exploring methods pre-

viously developed. In this study, for the soil condition in each area, the

maximum drawbar pull and the motion resistance for each wheeled vehicle

were predicted by two methods-identified herein as the WES numeric and the

WES curves. Predictions for the tracked vehicle utilized only the latter

method since the WES numeric at «his time is applicable only to wheeled

vehicles.

F20

■-^s",

30. WES numeric. The development and use of the WES nuneric have

been described in several reports-0' and only the equations are repeated

here:

f. A , „

>/ :i - 0.8713 " ■'•^—

20 s & - ^'^'. ,^ + 0

(5)

co-

where ,

K = VffiS numeric

C = average cone "ndex of C- tc 6-in. soil layer

b = width of tire, in. I

d = diameter of tire, in.

W = weight, lb: in using the equations in this report, W was tained by dividing the gross weight of each vehicle by the number of wheels en which the vehicle was operating

6 = tire deflection, in.

h = section height of tire, in,

Pj. = towed force, lb

P20 = drawbar pull at 20 percent slip, lb

Equations 2, 3, and U refer tc a single wheel. Where the ccaaputed values

of P2Cr and Pt^ are use(i in this rePcrt in reference tc a specific

vehicle, they are considered as being equivalent; tc drawbar pull coeffi-

cient (DBP/W) and motion resistance coefficient (MR/w), respectively. The

relations expressed by the '.vSS numeric were developed frcr. êsts en lab-

oratory prepared soils of ur.iforrn strength and moisture content. More

recently, tests have been conducted at V.'ES tc determine the effects or

performance when the soil is flooded. Results5 have indicated that a -0

percent decrease in pull may be expected when the surface cf a ciav sell

is wet or flooded. Since the surfaces of the test areas in this study

P21/

;'

were predominantly wet or flooded, the Pgc/W values determined by equa-

tion h were reduced by kO percent and are identified as 60 percent drawbar

pull coefficient in table F6. The same reference indicated no reason to

alter the P./W values as computed by equation 3« These are identified

as motion resistance coefficients in table F6.

31. WES curves. The alternate set of soil-vehicle relations used

to predict maximum drawbar pull and motion resistance is identified as the

WES curves. Values of maximum drawbar pull, expressed as DBP/w , were

o'ctained from curves (fig. F13) developed in reference 6. These curves

Fig. F13. Performance of tracked and wheeled vehicles in the water- land interface, fine-grained soils

were derived from drawbar pull and slope-climbing tests of wheeled and

tracked vehicles on flooded and wet surface soils, which is essentially

the same surface condition that existed in the tests reported herein.

Values of motion resistance, expressed as MB/W , were obtained from the

deceleration relations given in plates F3 and PU. (An explanation of the

rationale is given in paragraph 35)- Values of both maximum drawbar pull

and motion resistance as determined by the WES curves for use in these

prediction^ are given in table F6.

32.

values determined by each method and a tractive force-slip relation were

used to adjust the pavement curves for effects of soil strength and wheel

or track slip to determine tractive coefficient-speed and drawbar pull

coefficient-speed curves on soil. An example of this procedure is given

Adjustment of pavement performance curve. The DBP/W and MB/W

F22

e"»«PWW ■r;

\

SPtlO. ttPH

a LIMITS OF SOTb STRENGTH PCftCENT StrP

b. DCT&RMINATION OF SLIP

/ ~ \ ' V ! \ I 1

> \ (

02 v^ , M^

IS 2» «PttO. MfM

ADJUSTMENT FOR SLIP

D. DERIVED DRAWBAR PULL COEFFICIENT-

SPEED CURVE ON SOIL

Fig. FlU. Detenr.ination of ioil performance curve and drawbar pull coefficient-speed relations for M35A1 at site Uv-S-3 .-

using the WES curves

for the WES curves method in "fig. ¥lk and table F7. In this example the

raaximvun drawbar pull and motion resistance values used to adjust the pave-

ment curve in plot a, fig. flk, were determined from the WES curves as

follows:

/ a.

b.

c.

The VCI for the M35A1 (table Fl) was subtracted from the

average 0- to 6-in. soil strength for the M35A1 tests at

site UV-S-3 (from table Fh) to yield the cone index points

above VC^; that is, 6l - 31 = 30.

The maximum drawbar pull, expressed as DBP/W , was read

at 30 CI > VCI, from the curves in fig. F13 (q-v.,

DBP/W « 0.280 when soil strength is 30 CI > VCI^ .

The motion resistance coefficient was determined from the

F23

/ /

: /'

curve in fig. d, plate F3, to be 0.100 for a soil strength

of 30 CI > VCI, (see paragraph 35)•

d. Maximum drawbar pull coefficient and motion resistance

were summed to give maximum tractive coefficient on soil

i' (0.200 + C.100 = O.380). The values thus obtained were

entered or; the tractive coefficient axis as shewn in plot

a^ fig. Fl'+j to limit the traction and speed indicated

* by\the pavement curve. 1 33- To account for the loss of speed as a result of wheel slip,

the speeds indicated or. the pavement curve (within the limits established

by soil strength) were reduced by the percent slip as indicated in plot b,

fig. flhi to yield the soil performance curve as shown in plot c, fig.

FlU. These computations are detailed in table F7. It may be seen that

the relation expressed in plot b, fig. FlU, shows a 20 percent slip at

the maximum tractive coefficient for the M35A1 operating on a soil

strength of 61 CI with a linear decay to zero slip at the point where

the tractive coefficient equals the motion resistance on pavement as

indicated in table 17,

3U. The drawbar pull coefficient-!?peed curve (plot d, fig. Flh)

was determined by subtracting the motion resistance coefficient

(MR/W = 0.100) from the tractive coefficient of the soil performance

curve (plot c, fig. FlU). The drawbar pull coefficient-speed curve is

the basis for the acceleration predictions described in the following

paragraphs. , ■ Acceleration predictions

35. In reference 7, Knight demonstrates the use of maximum draw-

bar pull to determine the capability of a vehicle to climb a slope and to

tow another vehicle. The predictions herein are based on the considera-

tion of drawbar pull as the force available to accelerate the vehicle.

From this basis the procedures for determining time, distance, and speed

for an accelerating vehicle were developed. The following example illus-

trates the piocedure for determining the first increment of velocity

char.re on. the drawbar pull coefficient-speed curve (fig. F15) • The other

increments Were hanllel in a similar manner (table F8).

F2U

f

Fig. F15. Drawbar pull coefficient-speed curve for the M35A1 at site hY-S-3 with the first increment of velocity change

indicated

0.30

0.20

v. 0. B O

0.10

tO 20 SPEED, FPS

The acceleration a fror. ^ to V^ equals the change in ve-

locity divided by the time required to effect the change :V •■d

may be expressed by equation 1 from paragraph 18: '

a = V - V _2 i _ 5.73 -'0 _ 5^:

\

b.

(V1 and V2 are given in feet per second in table ?S for each increment.)

Thejorce f required to produce this acceleration is equal

to the hass (w/g) of the vehicle .times the acceleration.

lM = l(^) (5)

c. The f<m$ available to produce the velocity change frcr. 7,

to V^'is the average drawbar v-xil that can be developed from V^ to V .

f$5

1

DBF, DBF. -rr-^ and ' ,, ■ are given ii, table F8 fcr each increment. W A

The tin» t1 required fcr the force available DBF. to ef-

fect the velocity change is found by substituting the force

available D3P for force required F in equation 5 and

-earranging:

öBP = J1|1L_I1 . (v)

V - V -, * -1 1 = 141 = 0.6U sec

/DBP\ \ w ;

9.00 g

e. The distance d the Vehicle travels .In effecting the ve-

locity change fror V'to V„ is found by multiplying the

tine by the average Velocity V :

- 2 m o y.7^ u 2<88 ^ (8)

/

t = 2.88 x 0.64 = 1.81; ft (9)

/

Y

v^loeity from V to V divided by the tine ■ required to .;

vinil

\ \

Valued of V ,;V2 , V , DBP^W , DBPg/W , DBP/W , DBP/w x

t g , t , i , cumulative tine, and cumulative distance for

•i . the example (fig. ?15) are given in table F8. The compu- 1 tation of the effects of a gear change While the vehicle is

accelerating is given in plate F6.

Deceleratior. predictions

y 36. As stated in paragraph 18, when the acceleration is a negative

value (as wher. the vehicle is slowing down), it is termed deceleration.

The rationale ar.d the method'of predicting the speed and distance traveled

for a decelerating vehiele are as follows: ' , . V m V

f. 2 '1 —' Using the basic equation 1 » -a , the change in «t

\

F26 -. ^

,

effect that change is the deceleration when V1 > V2 .

The force required to produce this deceleration is equal to

the mass w/g of the vehicle times tiie deceleration:

l^) F

/

The force available ô produce t'iis deceleration in the

rolling tests (braking force is discussed in paragraph 37)

is the notion resistance M?. . Substituting into equa-

tion 10

(10)

•|M v - v1

d. Again, from the basic equation ^—* = -a , -a may be

substituted into equation 11 and the equation rearranged:

e. Or \ *

/ lM = ^ (13)

f. Speed at the end of any increnent of velocity change may be

determined by the equation

1 V2 = V-L + at , V (l^)

( a may be either positive or negative)

g. When V. is equal to/zero, equation lU becomes:

.(fx|g)t ,. (15) /

'2 VJ= at

^ Or for any time increment from V1 = 0

V = at = (fxg)t " (16)

F27

<•

c.

Ar. exaraple of the computations for the prediction herein is

given in table,?0.

h. The distance d traveled during deceleration was predicted

by the general equation for distance while accelerating from

zero velocity:

, d = 1/2 at2 {^xg'jt (17)

An example of the computations is shewn in table F9«

37. The computations made to determine the speed and distance trav-

eled when the vehicle is decelerating by braking are identical to those for

when the vehicle is rolling except that a braking force is used in lieu of

motion resistance as the force available to decelerate the vehiqle. In the

predictions herein, braking force was assumed to be equal to tTie maximum

tractive force the vehicle could develop on the'soil conditions being

tested. This is admittedly a fairly gross assumption; however, the Results

(paragraphs Uo and following) were reasonable, arid the investigation of

braking force-vehicle-soil strength relations was beyond the scope 6f this

study.

Average speed predictions ,

38. When a section of terrain is of sufficient length for the ve-

hicle under consideration to accelerate to its maximum speed (for instance,

22.39 mph for the K35A1 at site UV-S-3, from table F7 or fig. F15), the

average speed is predicted by dividing the length of the terrain section

by the sum of the time required for acceleration to maximum speed, the time

traveled at the maximum speed, and the time required to decelerate from the

maximum speed to the desired speed at the end of the terrain station. In

the teslis reported herein, the test courses were not of sufficient length,

for the vehicles to accelerate to maxiiinum speed; therefore, the average

^peed was predicted by dividing the length of the test course by the sum

of the tine required to accelerate and the time required to decelerate.

The time required to accelerate and the time required to decelerate are de-

termined by establishing the point of intersection at which the speed-

distance curves for acceleration ard deceleration spian a distance equal to

F28

J

^^■V^^ *:^/- . ..: '■■■:■ ■ ... .^faßfgjggflßfM

the test length. The point of intersection is established by the simul-

taneous solution of the equations of the lines representing the increments

of acceleration and deceleration wherein the point o^ intersection occurs.

An example of the computations made to predict the speed, distance, and

time at the point of intersection of the acceleration and deceleration

curves and the determination of the average predicted speed for M35A1 in

test 269 E are given in plate F7. Predicted average speeds for the tests /^~'

opnsidered ih this portion of the analysis are giver, in table F2. As »

previously stated, it was not possible to make a prediction for all tests.

(Note ,,ke^narks,' column of table F2.)

39^ An example or the measured and predicted performances for I<35A1

test 269 R is shown graphically in plate F8. It may be noted in plate F8

that the driver executfed the upward gear shifts at speeds very close to

.those predicted as optimum for gear change. The dashed lines representing

the increments wherein gear shifts occurred in the actual tests are used in

the plate because the test data did not permit an exact representation of

speed during the l-sec time interval in which »-.he gear shift occurred. It

also appears that the 0.4 sec allowed for deceleration during gear change

may be too small a time increment. The measured average speed for this

test was 9.7 mph and the predicted average speed fusing the WES curves)

was 10.1 mph. A summary of M35A1 performance data taken during test 269 R

is presented in table F10.

\ Comparison of Measured and Predicted Average Speeds y

Wheeled vehicles —<**

UO. A comparison of the average speeds predicted using the 'tlES nu-

meric and using the WES curves Vith the average speed measured for the

jj\ wheeled vehicle tests is shown in plate F9. From the plate it may be seen

that the predicted -speeds were generally higher than the measured speeds, u'

although in many cases they were only slightly higher. Several reasons

may be advanced to account for the predicted speeds exceedii% the measured

speeds: , •

a. The hard-surface performance curves (plate F5) were ob-

tained with vehicles in near-perfect mechanical condition.

F29

/

-v.

\

{

There is no assurance that the vehicles used in the tests

reported herein were operating at peak efficiency, and any

loss in efficiency within the vehicle' itself would result

In a lower acceleration capability, hence a lower average

%stee-i under the conditions tested..

b. The tine allcwed (O.h sec) for deceleration during the gear v char.ge ray be insufficient, and any increase in time allowed

for deceleration during the gear change would result in a

lower predicted speed.

It would seer, derirable that the scope of future test programs of this

nature should include tests to determine the mechanical condition and maxi-

man traction capability of the vehicle on pavement and that tests be con-

ducted tc better define changes in velocity that occur during gear changes.

hlt The deviation of measured average speed from predicted average

speed Tor each prediction is shown in table ?2. The average absolute de-

viations for the predictions made with the WES numeric and the WES curves

are shown in the following tabulation:

::umber of Tests

Average Absolute Deviation, mph

WES Numeric WES Curves

I-35A1

All

2

it

IS 13

11

31

Brak- ing ' Wtal_

3.3

2.0

2.5

3.0

2.0

1.7

Roll- ing

0.7

1.1

1.7

3rak- ing

2.1

1.1

2*7

Total

1.3

1.1

2.1

2.9 2,k 1.1 2.; 1.5

It can be seen from the tabulation above and from plate F9 that the pre-

dictions made using the WES curves were somewhat better than those made

using the •.vES numeric for the Mljl and !-37, anjl that the predictions using

the WES numeric were slightly better for the ¥$$1* It can be seen, too,

th»t the deviations in predictions for the M151 and I-S5A1 tests that in-

v-lved braking were greater than those for the tests in which the vehicle

re lie A -t-r c a step. The average deviation for all wheeled vehicle speed

predictions was 1.5 mph using the WES;curves and 2.U mph using the WES

?30

C" ' 1 .

> *" 1 . 1

/ (

1 ■. ■ ' . J --r^

- /

W-ptr. -: ;y<=^- .^,-.^;» mmssmMmmm- mm

numeric. Of the 31 wheeled vehicle tests for which speed predictions could

be made, in 20 tests the average speed predicted by using the WES curves

was closer to the measured speed than the prediction made using the WES

numeric; in 9 tests the average speed predicted using, the WES numeric was

closer; and in 2 tests deviation was the same. In brief, from plate F9

and from the tabulation above, it would appear that while both the WES nu-

meric and the WES curves are acceptable for a first-generaticn node!, the

empirically derived WES curves yield slightly better predictions.

Tracked vehicles

m, A comparison of the average speeds predicted usir.g the WES

curves with the speeds measured in the tests with the tracked vehicles is

shown in plate ?10. (it will be recalled that the WES numeric'has not at

this time been extended to include tracked vehicles.) From plate FIG it

can be seen that all of the predicted speeds were higher than those meas-

ured in the tests, and there is appreciable scatter in the M29C data. The

factors mentioned in paragraph hO in regard to the wheeled vehicles are

equally applicable to the tracked vehicle tests and predictions. The

average absolute deviations in predicted speeds for the tracked vehicles

are shown in the following tabulation:

Vehicle

M29C

MU3

Both

Rolling

10

15

Number of Tests Braking

k 2

6

Total

Ik

J_ 21

Average Absolute Deviation mph

Rolling

2.7

1.7

2.3

Braking

' 3.8

1.6

3.1

Overall

3.0

1.7

2.6

It can be seen that the average deviation for the M113 predictions was much

smaller than the average deviation for the M29C: predictions. When it is

considered that the M29Cîsed in these tests was approximately 20 years

older than the M113, these data do seem to emphasize the need to establish

the maximum traction capability of the test vehicles on a firm surface.

F31

J

PART IV: CONCLUSIONS AND RECOMMENDATIONS

ft«

Conclusions

U3. Based on the analysis of the data presented herein and subject

to the limitations imposed by these data, the following conclusions are

offered: a. Performance of wheeled and tracked vehicles in soft clay

soils in terms of acceleration can be related to soil

strength expressed as the average 0- to 6-in. cone index;

however, the data secured in this program do not permit

defining the relation (paragraphs sk^nd 22).

b. Performance of wheeled and tracked vehicles in soft clay

soils in terms of deceleration can be Correlated empirically

with soil strength expressed as the average 0- to 6-in. cone

index. While the data collected in this program do not per-

mit a complete development of the relation, logical extrapo-

lations can be made (paragraphs 25 and 26).

c. While both the empirical WES curves and the semiempirical

WES numeric appear to adequately define the drawbar pull

coefficient-soil strength and motion resistance-soil

strength relations for use in a first-generation model the

WES curves permitted a slightly more accurate prediction of

average speed for the tests reported herein (paragraph Ul).

■ ■ . ■

Recommendations

It is recommended that:

a. Additional studies be conducted to improve and extend the

relations presented in this report.

Additional studies be conducted to establish other relations

and/or input parameters needed for the WES analytical model

suth as are posed by the following questions:

(1) What is the peak performance of the vehicle?

F32

(2) Does time required to shift gears vary with transmission type and vehicle, and if so, to what magnitude?

(3) Does braking force vary with speed, with soil strength, or with surface condition, and to what magnitude?

(U) At what limiting slip can the driver still maintain adequate control of the vehicle, and does this vary with speed?

0,

\

F33

LITERATURE CITED

1 Rula, A. A. et al., "Relative Off-Road Performance of the M60A1E1 and MBT-70 Tanks" (in preparation), U. S. Array Engineer Waterways Experi- ment Station, CE, Vicksburg, Miss.

2. Benn, B. 0. and Keovm, M., "An Analytical Model for Predicting Cross- Country Vehicle Performance; Appendix A: Instrumentation of Test Vehicles," Technical Report No. 3-783, July 1967, U. S. Army Engineer Waterways Experiment Station, CE, Vicksburg, Miss.

3 ->eitag, D. R., "A Dimensional Analysis of the Performance of Pneu- matic Tires on Soft Soils," Technical Report No. 3-688, Aog 1965, U. S. Amy Engineer Waterways Experiment Station, CE, Vicksburg, Miss.

U. Richmond, L. 1. et al., "Aircraft Dynamic Loads from Substandard Land- ing Sites; Part II: Development of Tire-Soil Mathematical Model, Technical Report AFFDL-TR-67-1^5, Sept 1968, Air Force flight Dynamics Laboratory, Air Force Systems Command, Wright-Patterson Air Force Base,

Ohio. ' , . . 5; Smith, J. L., "A Study of the Effects of Wet Surface Soil Conditions

on the Performance of a Single Pneumatic-Tired Wheel, Technical Report No. 3-703, Nov 1965, U. S. Army Engineer Waterways Experiment Station, CE, Vicksburg, Miss.

6. Blackmon, CJ A., Stinson, B. G., and Stoll, J. K., "An Analytical Model for Predicting Cross-Country Vehicle Performance; Appendix D: Per- formance of Amphibious Vehicles in the Water-Land Interface (Hydro- lopic Geometlrv), " Technical Report No. 3-783, Feb 1970, IK S. Army Engineer Waterways Experiment Station, CE, Vicksburg, Miss.

7 Knight, S. L, "Trafficability of Soils; A Summary of Trafficability Studies Through 1955," Technical Memorandum No. 3-2U0, Ihth Supplement, Dec 1956, U.i S. Army Engineer Waterways Experiment Station, CE, Vicks-

burg, Miss. 1 • ' .

Depkln R. F., ^Wheeled Vehicle Performance Data Consolidation," Re- port No. DPS*2U10, June 1967» Aberdeen Proving Ground, Md.

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_- j\ ^j *> tn ■ t j\ ^^ VL> wrtjr» *> H • « • * • ■ -v pn »-■ *> u% Jl î ^* ■-•'"■.. rt r» M ai w i ♦ t i ■ * • i • + ♦ f • f ♦ 4 • ♦ ♦

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x ä x x ac XX35Äa äääIO —

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85^ ^ H H

H ^r O U4 o

at • a ojo o

o • ^ 5 6x

rn t^-1^ c* **> —110« ». ^rf —. ^, —i -v •-■ • •• a • • • a a a • •••

OOO OOO OOOOO OOO

t> lf\ lA Q tf\<a| O IA -"\ »

CU C- <".

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f»1) oo fî H^Q ^. O C c. c\j r- Tw FH c^ r, cu

ssosea âcnQ ^rssmin gj {£ at

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•(DA

fli O J lA a> ^ 5; «I r!

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x i: -^ s m • ^2: P H m p4 ^ -; A

<M "c. :. c. c. ™ ?n

-H C. ^C J IT*

/ '

' ■- , _. i f

Table F3 ■

, SuEmar; ■; of Soil Classification I )ata

J V rest Depth

in.

0-6 6-12

Percent Fines

90 89

Atterteir^ Limits uses

h Area Site ' , LL ■

^70

PL

25 23

PI

kl

Soil Type

Prah Euri ' ^y-3-3 ■ CH CH ' .

■ -..

Phet Buiî MRDC-X10 0-6 6-12

93 •' 99

51 56

2k 25

27 31

CH CH

i

3anut 'PraJ •-.an NKDC-Ä^ -0-6 ■6-|2

97 97

81 73

29 26

52 hi

CH CH

f / MPDC-Xr. 0-6 6-12

99 76 85

29 29

hi ' 56

' . CH « CH

.'.!RDC-Xt: 0-6 , 6-12

97 99 ■

102 lk9

33 35

69^ 41U

CH ', CH"

-.••

V

\N

\ , :..:±

' 1

i -i-7*-

\ ■

'I

fs

17\ r-i

I .

a \

—r v.

it

\

3

< -< »-I H <-) I ' \

-v.. —f

' Tacle ." 6

^•x-trjxv;; of atst Urs-j .'i'c^-ic''- Z^XICXB r^ri'ojrTâjice

jTES Curves .-.ction ,

.r-x,.-ä'xv Juli heslntance

1-51DC-X

^27-

Ib

i y

j,tfl

Coem- 1b cisnt

' 30c\ D,10

;.C>c 0.10.

;>^ 3.115

385 0. IS 5

47-3-3 . 5&

:^c^10 50

WS)0&2 , 35

msoK, -,0

. 7.6 S7>v >;371-

6.6 2121 0.204

-.7 1322 0,177

-o 9^7 ■' o.i3r V822 :.iit 127:

%;? ;.C-0 2166

37- JfOSd, £4)17

6-^2 .. ,r.6' 1c--

.29 7^7 0.10

r27 ' 7-7 3,10

■ 22 Ö56 0.12

17 —yfl 0.13

? ©

W-3-3 61

:^c-x10 46

34i

4V-S-3

MRDOX

JßOC-X

MRI)C-X

10

-V-S-;

MREC-X,

5S

52-

30

1c

61

^5 43^ 0.22; 12- a.ofcj >iK)f

la 23oi (o.i-5 I>7J 0.10? ^535

3,^ 12> 0.067 3129 :).16S i;^

MU3

1931 O.iO

^125 S.ll

3-77 ^.ie

1036 3»'305

17—^ ' ' ■'

771 3,128

:72

Tl*

fft

.IOC

.no

2163 OtO^c

Table F?

Detenr.ir.ation of Soil'Performance >Curve for MBÂl at Site UV-S-3

W

V

Tractive Hard Surface Slip«* Speed on Drawbar Coefficient* Speed,* mph

CO

* Soil, mph Coefficient

0.6^9 0.6^9 2.5 ': ■;

0.582- ' . ' \ 3.5 •■ 1

O.i.73 . M ■•

■"!

. i

. 0..380*' , -.9 ■ 20.00 3.92 0.280 0.365 ' . ' 5.0- •• 19*3.4 •. . lf.0U • 0.265

- 0.35$-\ ' ' .5.5 ■ • ,- 18.56 4.48 0.255 ' ■0.319 ^ ■ 6.5 16.50- • . ' . 5.^3 0.2J.9

. | 0^278 1 7.0 • •' ■, IV. 14 ■ 6.pi 0.178 .;.0.'227k ' .... s 8.0' -. 11.21 ' 7.10 0.127

0.221 10.86 ' 8.1+6 0.121 - 0.177 •^13.0 , 8.33 11.91 0.077

•. 0.162 lV«0 7.^7 12.95 0.062 0.1U1 ' - 14.2 . 6.26 13.31 O.OUl . 0.132 ' 17.5 5.75 16.U9 O.O32 0.100*t 23.3 3.91 22.39 • 0.000 / ;

' 0.093 25.0 ■ / f

0.072 /~\ , 29,0 0.066 v 3^.6

' ' 0.05i 40.0 " • o.09 . ' U6.5 \ 0.047 ^9.5 •...' « ' « o.oUi ' 53.0 0.036 57.^ l

0.032* -.■ . 60.O -kk

.

♦ From table'^5. j 1

, TC - 0.032 .■ . ^

1 *♦ Fror. fig. nh, sup = Q^^ . ' 1

1

, DBF .MR i + \

*

from table F6.

■ ' . , ., V

13

tt '# from M

talble F6.

tffil «i on pavement from table F5. if

Ixar.ple:

Speed on hard surface - slip - speed on soil

or kHi'm^)= 3-92 ■' " ■ ' . A

/ lable f8

Cccaputatlor. of Predicted Acceleration Data for M35A1 at Site 4V-.:-

1 fps

0.00

5.7rj

5.93

6.57

7.9^

8.31

IO.UI

t9.12

10.U

12.Ul

17.1+7

18.99

17.70

18.99

19.52

2U.18

2 fps

y

JSL. ™\ 'wy* ^ im\

Cumu- li ime Distance lative

ime

5.75 2.88 0.280 0.230 0,260

5.93 5.®» O.rô o^^ 0.27"

^.57 ' ^.25 0.2f5 ^>.255 O.T'O

7.9^ 7.26 0.2^c- 0*219 0,237

8,Sl 3.38 0.219 O4I7B O.196

10.1*1 9.^1 0.173 0.127 O.l'r,

9.If' 9.77 ' -- -- 0.100

10.Ul 9»77j — 0.127 ' 0.127

12.Ul ll.!*l| 0.127 0.121_0.12lt I

17M 1U.9I+ 0.121 0.077 0.099

18.99 18.23 0.077 0.062 0.070:

17.70»« 18.3U -- ' -- 0.100

18.99 18.3h — 0,062. 0.062

19.52 19.2^ 0.ÖC2 o.oin 0.052

2U.18 21.85 0.0U1 0.032 0,036

ISM S8,5i 0.03? c.ooo . 0,016

m . (t) (d) / / z<?c ft

'.00 o.ru 1.3U

8.75 o.or 0.12

8,36 0,08 0,50

■ •' 1 . 1,31

''.'•7 0,13' 1,09

-.r

■3 OO 0.1(0 3.91 1

.':.03 0,32« 3.1? 2

3.99 o.so 5,70 2

'.13 . 1*59 no • T ■_

2.25 0.'"J 12,M) i,

o; cp ■0.-0 ■ .7,3)4 (^

1.99 n 0 11.vf ■

1,67 C '' 6.16 jS

1,16 I. r;p 87, JU 10

0.K1 16.98 U8U,10 07

r;.

60

l'-

37

'V:7

Cumu- lative

Dictanctr V2 ft mrh

• l.Bh - ,"2

1,96- it.(A

,".''■' J,,l»8

v ,77 c.!4?

■ ■•. 9l 6,01

,'.o- 7.10

1 .Of

.:'l 11,91

0 12."»,

.r: 11.93

,17 12,S>5

• t ' 13,31

,17 1 •'.■';'>♦

#27 32,39ft

Uote: V = speed at teginninr of increment 1 ■ ' 1

V_ = speed at end of increment

7 = average speed for increment

Converted to feet ror second

DBF speed curve, fi /, ai

fron

id table

DBP; I = maximum dravfcar null/■•■•eicht at speed V

w 1

DBP0

—— = maximum drav/lar null v.-ei.-ht at speed V0 W ' ^

Equations:

- Vl + V2

0BP. DBPg __ __

■ir*-

.tt

Gear change, see plate j6. Gear change. Point A, plate F7. Point B, p^te F7.

-speed cur/c, fig

f =

t ab ie

v2 'l

BB| v g

d = Vt

,,.v. , ,;

Time sec

0 1 2 3 k

5 6 7 S

' 9 10

Table F9 -

r^^f.inn of Wm& n—•>"rftti0n ^^ fnr'M^5Al at- Site UV-S-3

m _w o 0.100 0.100 0.100 0.100

0.100 0.100 0.100 0.100 0.100 0.100

- 2 ft/sec |

o.ooo- 3.216 3.216 3.\2l6 3.216

3.216 3.216 3*216 3.^16 3.216

/ 3.216

Example: . •

For Speed at 5 Sec

V = at

v>(fxs)t

v = 3.216(5)

V '^'16.08

Speed

0.00 3.22 6.1+3 9.65

12.86

16.O8 19.30 22.51 25.73 28.9^ 32.16

J2E2_

0.00 2.19 U.39 6.59 8.77

10.96 13.16 15.35 17.5^ 19.73 21.93

Distance ft

0.00 1.61 6.U3 1U.U7 25.73

U0.20 57.89 78.79 102.91 130.25 160.80

270.3 270.3 270.3 270.3 270.3

270.3 270.3 270.3 270.3 270.3 270.3

For Distance at 5 Sec

d = § at2

d = I <;3.216)(5)'

d = U0.20ft

Distance from

Beginning of Test, ft

270.30 268.69 263.87 255.83 2M+.57

230.IO 212.Ul 191.51* 167.39»* lUO.05 109.5P

16.08 fps J 11.0 mph 270.3 - ^0.20 = 230.10 ft from beginning of- test

* Point C, plate F7. ** ■ foint D, plate F7.

■

Table FIO

-

Time, sec Distance, . ft Average Speed fps mph

Start of Increment

End of Increment

Start oi' Increnent

End of Increment

0 1 0.0 3.6 3.6 2.5

1 2 3.6 13.3 9.7 6.6

2 3 13.3 23.8 10.5 ?.2

3 U 23.8 36.7 12.9 8.8

k 5 36.7 52.8 16.1 11.0

5 6 52,8 71.1 18.3 12.5

6 7 71.1 91.1 20.0 13.6 <T

a

7 8 91.1 110.7 19.6 . 13.0

8 9 110.7 131.4 20.4 13.9

9 10 131.^ 152.4 21.3 .' 14.5.

' 10 11 152. U 174.6 22.2 15.1

11 12 17^.6 197.1 22.^ 15.3

12 13 197.1 217.6 20.5 14.0 ■-

13 ih 217.6 • 234.6 17.0 11.6

Ik 15 23^.6 247.3 '..■ 12.7 8.7

15 16 ' , 2U7.3 257.2 9.9 6.7

16 17 / .257.2 264.3 -.7.1 4.8

17 18 26U.3 268.7 4.4 3.0 -Rr ■

18 19 , 268.7 270.3 : 1.6 l.l'

as

. *>

; ■

o.e

0.4

0.2

/ /

• 3«

•4

»2

- - ■

"•o

l3O0»o

lOoOlt TOT

:

I I 0. 5

*

3 j s < 2

0.2

0.4

0.2

MI5I

34A 31*

*?5

28 *21

2t« *2T

k24

»22

b. M37

4«, 45,

3».

44m4l 42ffl43

-40 ■37

.36 *39

20 ' 40 - , «0 SO AVERA6C 0- TO «-IN. CONE tNOEX

c. M35AI )

tEGEND OPEN SYMBOLS INDICATE BANE SURFACESrr^ CLOSED SYMBOLS INDICATE CRASS- COVERED SURFACES. NUMBERS NEAR PLOTTED POINTS ARC CODE NUMBERS FROM TABLES F2 AND F4.

too

ACCELERATION RELATIONS FOR

WHEELED VEHICLES

PLATE Fl

■X ■}

0.4

0.2

>■

I 0 O , 0 * z o

< I u •/ J u u o «

I i « s

0.2

590

»O AM

ss -O-

88 I ♦

I «7

SO

8 $2

20 40

O. W29C

61

|A«7

AS

20 . 40 •"

AVERAGE 0- TO 6-IN. CONE INDEX

b. Mil3

1 '/.

■/•?%

LEGEND

OPEN SYMBOLS INOlCAtE BA«E SURFACES CLOSED SYMBOLS .NDÂTE ORASS-COVERÔ SURFACES

NUMBERS NEAR PLOTTED PO-NTS ARE CODE NUMBERS FROM TABLES F2 AND F4 ,

ACCELERATION RELATIONS FOR

TRACKED VEHICLES

'LAI3 F2 fe,

v_

fv

t

i H B f

At .1 1 1^ >♦ »y. i »k, .«' /.•| 4«

■ 'V 0.1 _4_J—|

U»—^r 1 ^ 1

t ,

,

-=■»0— 1 —^

%

so

b. M37

TO ° M

i'

' 1 l

S».^ \

. L

« M

|^—KC/,

1 . •'

•.i

A

CONt INlic« POINT« «OOVC VCI,

d SUMMARY

UOENO

Onn tTMMLt INOICATI OAOC SUHMCCt. CLOtCO STMNkt INOICATE CMM- c«vc«to «vir«ct» NWMKM HCM PLOTTIO POINT« MC eoec NUMMM FOOM TAOLC* r< AND r4 DECELERATION RE1-ATI0NS

FOR WHEELED VEHICLES

PLATE F3

s Q \-

/

0 2

>

5 °-' \ z o

X o

^

1

- f

n67 *" 1 i M •3

vci,*-

1 f

5 (t

10 20 30 40 50

»VERACf 0- TO e-IN CONE INDEX

b. MII3

60 70

%

0 3

0 2 —

0.1

1 \

•

\

\

^4 I 0 0 I 0 -fc-i

A ( (

10 20 30 40 CONE INDEX POINTS ABOVE VCI,

c. SUMMARY

50 •0 70

LEGEND OPEN SYMBOLS INDICATE BARE SURFACES CLOSED SYMBOLS INDICATE CRASS- COVERED SURFACES. NUMBERS NEAR PLOTTED POINTS ARE CODE NUMBERS FROM TABLES F2 AND F4.

DECELERATION RELATIONS FOR

TRACKED VEHICLES

J

FLAT2 75

2 £ <

Tut

l-l =

T > " 5

< < J

> >" ~

> *" *" ? 1 M > O 3 J r c - Zf c ^ a _ _ -

z - - 5 -

o ? ^ >

i >

2 Z

< ^

I - ä i>

ü UJ Z

V <0 z o

1- z 5 H < 2 H i S

ä

51 t

Q. 2

Ul u I G

EA

R C

A

CC

EL

d ^ O u O 23 »1 T5 O I

> ^

1

c. <

X z -3

■1

ir — 2 — T < 5 * _

z ? > z ^" c

? - Ä ■J- h ^ s <

5 z t c 1 Z 'T' ►• -

- i 5 =

- - J

". ■-> z < (1 z.

> Z u - M M

f •;■ > »- a Z < z s 1 > r c < _

z I ;- f_ ~ 1- >

r i Z < ^ 5

< 3 r

r < E = z < - h

K < '— ir Z * < ^ _

< > 1 1 r

5 I — r - ^ < i

? h - 2 — Z

— a r,i 1 ä _ . _ * - _ < u K

X > _ * 1 J I

3 - o < — < ~ > 0

ff «1 . / < ■<

f --- — 1 -

1

\ —i

■ ^K S

3 X? 1 /* 0 i /

_ L?< •

- < - ? E i; S K u. - >

£ " 1 e5i j 51

Stf J 'a33dS

I * »- ■s. _

■■, ^ > "

c i - i» »• ■ E >- z «; z Si? c t C 5. I | I- II M I.

H 5 a. IS •. ij

- 15 o u

y s 3 X c o p s a

< 2 z >

? I >1 2 i i- a. > I -i

c c z < c

m U

< >

X

- s. ■* Z ~

UJ Z

li I- H t- a

o y

2

o u u 0. to a. UJ o» 1 It l- Ui (O

$ UJ

a < UJ in i- m u 2 o u oc Q.

z ^ *B s < - • - p r < -

fc - z

- - - * — z ^ _

r Z ~ <

z < =

— : r z

: - £ r 2 ■

_ z x £ 5 ^

: ^ 5 -

z z *- c ^ 5

_ > - - z - < 5 fe i to o a - * r - r ^ E ^

SdJ 'C33rfS

♦ •« -I!

^

V

f

PLATE ?:

I« 20

iJC y

.« •«o» A / /

s

9 o« y •4-<'

12 ■i r I6ANDI7-; s

a

w

_J

4 /

12 If 20

o. MI5I

— / k ~/ /

33^ /

A23

/ 12 I« 20

12

/ ^ /

4-//

/ 12 M 0 4

MEASURED AVERAGE SPEED, MPH

c. M35AI

NOTE: SMALL NUMERS NEAR PLOTTED POWTS ARE C00C NMBERS FROM TABLE F2.

COMPARISON OF PREDICTED AND MEASURED AVERAGE

SPEEDS FOR WHEELED VEHICLES

FLAT£ r

\

, -

i

s r- « \

S<'0

i 0. z G U W a M

o <

I < O « u

■

Q \ Z en

<

Q UJ 1- Ü

SP

EE

D

ICL

ES

o ^F. UJ o u a <^

.v Q.

b.

AVE

R

:KE

D

O Z o^ o ui a: ED < (OK £ <P 2 Su. O 2

IE 3 to < U

i

HdM •a33elS 30va3AV a3XDia3Hd

m . I- N z u. 5 w a J

I- z 0 o J E a. k.

1 ir u u

■ w s s 3 O z u

Ü 1- o z

DISTRIBUTION LIST FOR TR i7a3. APPENDIX F

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ATTN: ATLOG-E-MB

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2

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Commndant. U S. Army En^neer School. Fort Bdvoir. Va. 22060 ATTN Ubrary

r-ymmxuUnt Armed Jcrce» Staff CoUeqe. Norfolk. Va. 23511 ATTN Library

Commndant, U. S. Army Siîal School. Fort Honmouth. N. J. 07703 ATTN Litrary

Commandajt. U. S. Military Academy. West Point. N. Y. 10996 ATTN Library

Command«« Commaid and General Staff Cotieqe. Fort Leavenworth. Kaos. 66027 ATTN Aichivei

#" Director. U, S. Army Devdopment and Proof Services. Aberdeen Proving Ground. Md. 21005 ATTN Technical Ubrary

Automotive Engmeerinq Laboratory (STEAP-DS-LU) Automotive Division (STEAP DSTU)

Director. Institute for Defen» Analysis. 400 Anny-Navy Drive. Ariington. Va. 22202

President. U. S. Army Ardlery Board. Fort SB. Okla. 73503

President. U. S. Army Aviation Test Board. Fort Rucker. Ala. 36360

Ptendent. U. S. Anny Air Defense Board. Fort BUss. Tex. 79916

President. U S. Army Infantry Board. Fort Benntng. Ga. 31905 ATTN: Tactical Section. TIS

President. U. S. Army Infantry Board. Fort Benning. Ga. 31905

President. U. S. Anny Armor Board, Fort Knox. Ky. 40121

CDJCPAC. Camp H. M. Smith. Oahu. Haw» 96822

LTC E. W. Stewart. U. S. Anny Combat Developments Command. Institute of Land Combat Fort Bdvoir. Va. 22060

President. U. S. Army Airborne. Electronic-Special Warfare Board. Fort Bragg, N. C. 28307

Director. U S. Army Cold Repons Research and Engineering Laboratory. P. O. Bos 282. Hancv-r. N. H. 03755

ATTN AMXCR-PI (Mr R. E. Frost) Library

2

/>.

No. of Address Copies

Navy

Comnmdinq Officer. Office of Naval Research, Surface and Amphibious Program» (Code 463) i Washinqton. D. C. 20390 <■ ^

ATTN: Naval Applications Group ~'"^^^-^'

Qa—Mfcj Officer, PHIBCB One. U. S. Naval Amphibious Base. Coronado. 1 San Diego. Calif. 92118

Commanding Officer. PHIBCB Two, U. S. »aval Amphibious Base. Little Creek. 1 NorfoU., Va. 23521

Coaunnduiq Officer. Office of Naval Research. Washington. D C. 20390 1 ATTN: Earth Sciences Division (Code 410)

CbmmaDding Officer, U. S. Naval Photoâphic Interpretation Center. 4301 Suitland Road. 1 Wariiington, D. C. 20390

ATTN; Library ^

Commaiding Officer and Director. U. S. Naval Civil Engmeehng Lab. Port Hueneme, Calif .fi> 93041 1

Commandant. U. S. Marine Corps, Vftuhington. D. C. 20380 ! ATTN: A04E

Chief, Naval Facilities Engineering Command. Washington, D. C. 20360 1 ATTN: Code 70, Department of the Navy

Director. Naval Warfare Rewanh Center. Stanford Research Institute. Menio Park, Calif. 94025 1

U. S. Army Attache. American Embassy, U. S. Navy. Box 36. FPO New York 09510 2

Air Force

Headquarters, USAF. WaAington. D. C. 20330 ATTN: Deputy Chief of Staff. Research and Development (AFRDC) 1

Deputy Chief of Staff. Director of Civil Engineering (AFOCE) 1 Director of Science and Technology (AFRST) 1

Air Force Office of Scientific Research. Building T-D. Washington. D. C. 20330 1

Commander, Air Proving Ground Center, Eglin AFB. Ha. 32542 1 ATTN: ADTC (ADBPS-12)

Commander, U. S. Strike Command, Mac Dill AFB, Ha. 33608 1 ATTN: J4-E

Director, Terrestrial. Sciences Laboratory (CRJT), Air Force. Cambridge Research Laboratories. 1 L. G. Hanscoi« Field. Bedford. Mass. 01730

Air University Library. Maxwell AFB, Ala. 36112 l

I

No. of

Address CoP*"

20

Oth« Govcnunwit Agtndes

Defen» Uocumenution Cent«. Cameron Station. Aiexatdha. V». 22314 ATTN Mr. Myer Kahn

Ubrary. Division of Public Documents (NO CLASSIFIED REPORTS TO THIS ADDRESS). 1 U S Government Pîntinq Office, Warfunqton. D. C. 20402

Library of Congress. Oocuments Expediting Project, Washington. D C. 20540 3 I

Duector. Project My^qan. Willow Run Laboratories. Ypalanü, Mich. 48197 1

Oiief, Source^lâtenal Unit. Branch 7f Military Geoloqy. U. S. Geological Survey 2 WdJliinqton. DC 20242

Chief. World Sou Geography Unit, Sou Survey Interpretations. USDA Soil Conservation Service 2 14th St and Independence Ave. SW, Washington, D. C. 20250

national TiUage Machinery Laboratory. U. S. Dept of Agriculture, P. O. Box 792 1 Aubum. Ala 36S30

Colleges and Univertities ^ • , .

University of Arkansas, CoUege of Engineering. FayetteviUe. Ark. 72701 ,

Dr Daniel C Drucker, Dean, CoUege of Engineering. University of Illinois. Urbana. IU. 61801 1

Massachusetts Institute of Technology. Cambridge. Mass. 02139 AITN Soil Engineering Library

Dr Emu H Jebe. Operations Research Dept.. Institute of Science and Technology. Univeriitv 1 of Michigan. Box 618, Ann Arbor. Mich. 48106

Prof. L C Stuart. University of Michigan, Ann Arbor. Mich. 48104 1

Prof Ralph E Fadum, Dean. School of Engineering. North Carolina State CoUege of the 1 University of North Carolina. Raleigh. N. C. 27607

Davidson Laboratory. Stevens Institute of Technology. 711 Hudson Street. Hoboken. N. J. 07030 t

New York University. University Heights. Bronx, N. Y. 10453 - ,^ 1 ATTN Enqineerinq Library '-

Other

Battelle Memorial Institute. 1755 Massachusetts Avenue. N. W„ Washington, D. C. 1 ATTN RACIC /

Enqmeennq Societies Library. 345 E. 47th Street. New York, N. Y. 10017 1

GM Defense Research Laboratories. General Motors Corporation, Box T, L Santa Barbara. Calif. 93191

l4of. Robert Horonjeff. 3643 Brook Street. Lafayette. Calif. 94549 1

Research Analysis Corporation. McLean. Va. 22101 ATTN Library

WNRE. Inc.. Chestertown. Md. 21620 ATTN Mr C. J- Nuttall, Jr.

1

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ii K^PfcBHBWlB? MOT»« • a. s»OMtoiiiM«Mii.iTaav acTiviTv Adrancei ?.ese&rcr. Projects Arency and Directorate of levelopcen*. and Hr-gineerin« U, 3. Ar-rr Mtteriel ri—■nil

«ere conducted vith t'nree «heeled and two lit. nnnif 3ixty-six acceleration-deceleration tes tracked vehicles at five sites in Thailand. The principal conclusion froc these test VRS that vehicle deceleration in soft clay soils can he correlated vi*.h soil strenrth expressed as the average 0- to c-in. cone index. The analysis indicated that acceleration increased vith an increase in soil strength, cut no definitive correlation could te established. Saniempirical and enpirical relations vere used in a first-generatio: analytical nodel to predict average speed over the tes* courses. Tonrarisons of neas ured and predicted sreeds led to recrrriendations for specific additional studies to in- prove the reliability of the '.iTFc anal:,-tical model

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