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California Test 301
<br /> 1978
<br /> 3.figure 15 shows general curve configurations of loads (HW1,) to be expected during th.:design
<br /> R-value.versus exudation pressure,for ranges of pros- period, ir, )-cars, Following construction. Calcu.
<br /> sures and types of materials indicated.This chart is lations involve multiplying lbe atiie group con-
<br /> intended as an aid to the technician in snaking in starts listed in Table 1 by the average daily
<br /> interpretation and analysis of the test data, truck traffic (ADTT) for each respective axle
<br /> C.R-VALUE BY EXPANSION PRESSURE METHOD: group.This product is then multiplied by a fac-
<br /> � 'hen a material expands, the R•value of the tor'which provides for the anticipated increase
<br /> in traffic for the particular axle group during
<br /> material is lowered. This results, primarily, from a the design period.This Calculation gives the av-
<br /> loss in density due to disruption of the material.Since erage yearly EWL in one direction.
<br /> the espansian potential of the material varies in-
<br /> versely with respect to its moisture content, the TABLE 1
<br /> thickness, or weight of cover, necessary to prevent EWL CONSTANTS
<br /> expansion also varies inversely with respect to mois- �—
<br /> lure content.In the case of the R-value,even though °o°r'�`�"i c•n,22V
<br /> the R•vahle itself varies inversely with respect to 3 s3"
<br /> moisture,the thickness cf cover necessary to prevent s 1,330
<br /> lateral deformation of the material under a load var-
<br /> s 1;�
<br /> ies directly with the moisture content of the mater i- By taking a summation of the products, the total
<br /> al. EWL repetitions for the average year are deter-
<br /> A given material is tested by making several test mined,and the Design EWLrepetitions are found by
<br /> specimens with a range of moisture content and de- multiplying the EWL repetitions for the average
<br /> termining for each one its R-value and expansion year by the number of years in the design period.
<br /> pressure at that particular moisture.The thickness of This method of calculation is illustrated in the follow-
<br /> cove, required for the R-value and that required for ing example:
<br /> the expansion pressure are calculated and plotted AnticipatedAD774
<br /> against each other and,since they vary in opposite No.of EIVL .9rginning of .Anticipated EIVL fin•
<br /> .isles Constants Design Prriod lccrea.+e Factors .ttle Croup
<br /> directions with respect to moisture, the curve con- 2 use X so x 2.00 44.e11)
<br /> necting the points will intercept a balance line 3 930 X is X 1.80 30,100
<br /> 4 1= x 7 X 1.50 13.9w -
<br /> drawn through the graph. At this po--nt, the cover 5190 x is x 1185 106,2;10
<br /> required for both purposes will be the same. This 6 1.950 x 2 x 1.30 5.to0
<br /> equilibrium value for thickness is then worked back Total Average Annu31 EWL Repetitions.............. = 200's"
<br /> through the thickness equation to obtain an It-value. Multiply the Annual EWL Repetitions by the num-
<br /> This R-value is termed the R-value by expansion ber of years in the design period, for this case 20
<br /> pressure and it is detcrmined as shown in the follow- years.
<br /> ing steps. ENYL = 20 X 200,800 = 4,016,000
<br /> 1. Use back of work ca-.1, Form T.L.-361, for re- The EWL is converted to Traffic Index by .qua-
<br /> cording results of calculations (Figure 18).
<br /> 2. In this method,the R-value of the three speci- tion number 4 or by the conversion chart,Figure 16.
<br /> mens as determined above must be used to deter- (Equation #4)
<br /> mine corresponding thicknesses of cover. Since this TI.— 6.7 (EIf163/106)"Is'
<br /> involves the use of tLe thickness formula, which TI=6.7 (4,016,0001101}0.119
<br /> equates thickness in terms of traffic index and gravel =7.9 L?sc 8.0 since the TI value is always
<br /> equivalent factor as well as R-value,it is necessary to rounded off to the nearest 0.5
<br /> either assume or evaluate (a) the traffic index of the —
<br /> section under consideration and (b) the gravel 11 ns futjf rnnscrg.is.-rarer nasi}Truck atedic Count(rein the leers}.
<br /> r Wink of rhe drsiy;n]x-riwl to the anticipated cma,r of Iku•middht or
<br /> equivalent factor of the cover overlying the in.iterial asrragc,yrur of the dcsigu prriwi.Ircr cs.nnple,if past i-nic inform,-
<br /> being tested. lion indicalr,that the drily count for 6.�sle trucks will duuble Buri v
<br /> a. Tra>re Irrde.r C.ticrlatinus. A design traffic IR
<br /> the dosign prriml•and it is a•rtrcipalm Ihal the increase w ill he dime,
<br /> then the factor is calcul:dvd is follows:
<br /> --- der%till usually be made available t,y the Dis. -.i 2, '.,11 4. 0,,.1,1112=11 c t=111112_ is _
<br /> trict Traffic En incer. 1lowever, for the
<br /> g A zi=A,rtiripatsat lorrrasr Fact-ror Ihv 2i)vo:rr design 1e-rirA,
<br /> purposes of an example,the following problem .1,_:1n:ieip.rtrd:urfr at ilte 6cl;•unirg ur iLc drsiy„lx•rrod.
<br /> is worked Ocrt. Traffic is expressed in terms of •1)=Anticipaled AD'i'r at Ili i lid of the design period.
<br /> s Tal.,datrd constant%.nr for awragc Glifrrnia trurh tr4a3e,1W, lhror:ate
<br /> the number of equivalent 5,000-pound wheel i8rs.
<br /> 22
<br /> .tad.
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