1、Designation:D188314Standard Test Method forCalifornia Bearing Ratio(CBR)of Laboratory-CompactedSoils1This standard is issued under the fixed designation D1883;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.
2、A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope*1.1 This test method covers the determination of the Ca
3、li-fornia Bearing Ratio(CBR)of pavement subgrade,subbase,and base course materials from laboratory compacted speci-mens.The test method is primarily intended for,but not limitedto,evaluating the strength of materials having maximumparticle size less than34in.(19 mm).1.2 When materials having a maxim
4、um particle size greaterthan34in.(19 mm)are to be tested,this test method providesfor modifying the gradation of the material so that the materialused for tests all passes the34-in.(19-mm)sieve while the totalgravel(3 in.(75 mm)to plus No.4(4.75 mm)fractionremains the same.While traditionally this m
5、ethod of specimenpreparation has been used to avoid the error inherent in testingmaterials containing large particles in the CBR test apparatus,the modified material may have significantly different strengthproperties than the original material.However,a large experi-ence database has been developed
6、 using this test method formaterials for which the gradation has been modified,andsatisfactory design methods are in use based on the results oftests using this procedure.1.3 Past practice has shown that CBR results for thosematerials having substantial percentages of particles retainedon the No.4(4
7、.75 mm)sieve are more variable than for finermaterials.Consequently,more trials may be required for thesematerials to establish a reliable CBR.1.4 This test method provides for the determination of theCBR of a material at optimum water content or a range ofwater content from a specified compaction t
8、est and a specifieddry unit weight.The dry unit weight is usually given as apercentage of maximum dry unit weight determined by TestMethods D698 or D1557.1.5 The client requesting the test may specify the watercontent or range of water contents and the dry unit weight forwhich the CBR is desired.1.6
9、 Unless specified otherwise by the requesting client,orunless it has been shown to have no effect on test results for thematerial being tested,all specimens shall be soaked prior topenetration.1.7 For the determination of CBR of field in-placematerials,see Test Method D4429.1.8 UnitsThe values state
10、d in inch-pound units are to beregarded as standard.The SI units given in parentheses aremathematical conversions,which are provided for informationpurposes only and are not considered standard.Reporting oftest results in units other than inch-pound units shall not beregarded as nonconformance with
11、this test method.1.8.1 The gravitational system of inch-pound units is usedwhen dealing with inch-pound units.In this system,the pound(lbf)represents a unit of force(weight),while the unit for massis slugs.The slug unit is not given,unless dynamic(F=ma)calculations are involved.1.8.2 The slug unit o
12、f mass is almost never used incommercial practice;that is,density,balances,etc.Therefore,the standard unit for mass in this standard is either kilogram(kg)or gram(g),or both.Also,the equivalent inch-pound unit(slug)is not given/presented in parentheses.1.8.3 It is common practice in the engineering/
13、constructionprofession,in the United States,to concurrently use pounds torepresent both a unit of mass(lbm)and of force(lbf).Thisimplicitly combines two separate systems of units;that is,theabsolute system and the gravitational system.It is scientificallyundesirable to combine the use of two separat
14、e sets ofinchpound units within a single standard.As stated,thisstandard includes the gravitational system of inch-pound unitsand does not use/present the slug unit for mass.However,theuse of balances or scales recording pounds of mass(lbm)orrecording density in lbm/ft3shall not be regarded as nonco
15、n-formance with this standard.1.8.4 The terms density and unit weight are often usedinterchangeably.Density is mass per unit volume whereas unitweight is force per unit volume.In this standard,density is1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direc
16、t responsibility of Subcommittee D18.05 on Strength andCompressibility of Soils.Current edition approved Dec.1,2014.Published January 2015.Originallyapproved in 1961.Last previous edition approved in 2007 as D1883 072.DOI:10.1520/D1883-14.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 given only in SI units.After the density has been determined,the unit weight is calcul
