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tiT California Test 301 1978 lent of the lager.Sunt up the indi%•idu:al la%er gr"' tided oil the back of the work card l FiGurc JS). of cyui%':ilcnls to obtain 1he tectal graccl equivalent Note the thicE:ness rabic at which the etin•e 18). s{the system.Connect the point ntt Scale h r1, netting the points in (he cx:unple crosses the•!3- sentini this coca!grate!equivalent x'ith the I:uint degree balance line ({1.89').Concert this thickness on Scale I representing the actual thickness of the to 11-value with the design chart (k�igurc 19); corer materials and the intersection of Il,is line with u straightctlgt,intersect 0.59'an Seale 1 with with Scale }i is i}ic combined grace! equivalent with factor 1.3 on Scale 11 and read the gravel equivalent (C:,) for the c•oartbined layers• (1.33') on Scale C. Then, rotate the straightedge For convenience and a record, the thickness and about 1.33'on Scale C through a TI of 8.0 on Scale type of each ocerl:a}ing layer is entered on the hack Fand read in R-+'altic of 4S on Scale ii.This sol cs of work card along with the combined gratel equi%a- for the relationship: lent factor. (Note Figure I8 right hand side of card). c. Knotting the coruhinodgratc'lerluivalctilfactor �� J00 ^ (Cr(7)Jlf.O!13?(T!,] (cf) of the cover material and the traffic index ltecord this R-v:,ltie oft the wark card, for the road,use the design chart (Figure 19)or e• The R-%'ulue at equilibrium is established by tak- the design equation? ing the lowest value of the above two R-tapes (ECtt1:%tiP11 #J1 and the cover required cot responds to the it- -1•_ 10-0032 (r� (loo •- 1?)]/C, %•.title selected. to determine the"thickness indicated by stabi- 0. NOTES lomeler," corresponding with the R-%-slut by When determining Of for R-value calculations on exudation pressure of each specimen, and current contracts, it is necessary to refer to the car- record these data on.the back of the y:ork card rect t%pieal section in the contract special provisions. (Figure 18). T.,e enver thicknesses usod should correspond to the d. To determine the 13-value by expansion prea- section itself for the stationilig noted an the sample sure, it is firn st eccss:sry' to calculate the thick- ticket (Form T-101). resses of co%er required by ex-pansion pressure It is often convenient to express the thickness of for each specimen from the dial readings re- coyer determined from the R-taltte test in terms of corded oil the work caret.For design purposes the gravel equivalent as a temporary exped,,'nt the unit weight of cover is assumed to be 130 !%vhcn the t%'pes of cover materials to be turd are pounds per cubic foot.The expansion pressure either unknown or uncertain). The gravel cquiva- devicesareso calibrated that it isonly necessary lent,:as the name implies, is the thickness of gr wel to divide the dial readings by thirty to obtain required to support a given load,and is based upon the cover thicknesses in feet on the basis of this :o gravel equivalent factor of 1.0 for the cover inateri- :assumed unit weight. 1;ecorcl these values on aE.One of the principal advnntcages in using the gra v- the work card. If, in special investigations el equivalent is that it indicates to the designer what where more accurate information is available,it inaximum thicknesses will he required to meet the is desired to use a different unit%%eight of corer conditions of the soil and traffic of the proposed material,then the cover thicknesses May be de- project.Since a Of of 1.()is the Icntcst %:11110 used for %ermined from the following formula: design purposes,use of 1.0%sill result in the deterrni- (Equation #6) nation of the highest theoretical thickness reg;uire- T= ;(Bial Rcading X 10,000)1301 X (t3(1;1L') mentsfor:agiven R-yahaeand tr:tfficindex.Likcr%isr, where W = twit weight of co%•er over material be- `arty subsequent increase in the 1;ravef equivalent foe- ing considered for will ahyays rcduce the design thickness require- If the expansion pressure lit Iaounds per square rilent' Tile process of determining the gravel J 1 tquiwalrnt from Nacdesign chart (higurc 191 inerily foot is needed, it may be determined by the following Formula: consists of intersecting lite R-%:due at equilibrium ort Scale f-* :noel the traffic index on Scale F' %%'ith :a Expansion Pressure=4.33 X Dial Re,adingX 10,0011 straighte(Ige and reading its point of intersection on The determination of the R-value by expansion Scale C. pressure is accomplished by first plotting-thickness ,The destl,rt%-qua;ion is not altplirahlr to design of indicated by the st:abilometer.against thickness let• I ortland cement concrete pavements and no gravel dicaled by expansion pressure on the grip) pro- 'c 24