The results of these tests are used with the curves to determine the thickness of pavement and its component layers. As pointed out earlier, if necessary, the expected. California bearing ratio cbr test is run on soils to gauge the strength of the subgrade as compared to a dense graded aggregate. The maximum dry density and optimum moisture content, as defined below, is determined by establishing the moisturedensity relationship of the material when prepared and compacted at the modified aashto compaction effort at different moisture contents. The maximum density of a material for a specific compactive. Specimens compacted in the cbr mold at nearly saturated conditions were allowed to dry for. Cbr is the ratio expressed in percentage of force per unit area required to penetrate a soil mass with a. This plateload test consists of a reaction or dead load and a hydraulic jack with dial gauges. The cbr test could be used for running compaction control during embankment erection. The california bearing ratio, abbreviated as cbr is defined as the ratio of the test. Soil density standard vs modified proctor reinforced soil structures routinely specify that all soils be compacted to 95% of the maximum density determined by astm d698 standard proctor density for conformance with the design. California bearing ratio cbr, maximum dry density mdd, optimum moisture content omc, soil compaction. The line of optimum moisture contents is usually around 85% saturation and the optimum moisture content decreases with increasing compactive effort. This test method covers the determination of the california bearing ratio.
The virginia department of transportation vdot has been using its own virginia test method8 vtm8 to perform cbr testing. The california bearing ratio cbr is the most utilised parameter for dimensioning flexible pavements in tropical countries. Cbr yang direndam telah siap untuk dilakukan pengujian. Note 1 it is important that the water is mixed thoroughly and adequately with the soil, since inadequate mixing gives rise to variable test results. The california bearing ratio test is penetration test meant for the evaluation of subgrade. This test method sets out the procedure for the determination of the california bearing ratio. The classification testing reveled that tested soil is a poorly graded sand sp according to astm d2487. Pdf modeling of california bearing ratio using basic engineering.
Standard test method for cbr california bearing ratio of laboratorycompacted soils1 this standard is issued under the. The modified proctor test is of great importance and is widely used in the construction of roads, highways, earth fill dams, earth filling, airports, etc. It is a relative measure of subgrade soil or basesubbase aggregate strength. Have the student highlight key words in the directions andor questions. The pressure up to a penetration of 10mm and its ratio to the bearing value of a standard crushed rock is termed as the cbr. Soil is compacted in five layers, each layer being given 55 blows of the 4. A modified california bearing ratio test for granular materials. The california bearing ratio test is penetration test meant for the evaluation of subgrade strength of roads and pavements. Standard test method for cbr california bearing ratio of. He undertook a considerable number of tests in australia for obtaining the cbr,using staticdynamic cone penetrometersdcpscala, 1956. Modified cbr tests on geosynthetic reinforced soilaggregate systems 299 where e s is the standard compaction energy in kj m3 592, n b is the number of blows per lift, n l is the number of lifts, w is the weight of the rammer used in kn 4. The most recent revision tothis technical guide lg004 other than minor editorial changes is. The california bearing ratio test cbr, whichwas first developed during the early 1930s, is a penetration test,wherein a standard piston, having an area of 1935mm 2, is used to penetrate the soil at a standard rate of 1.
The california bearing ratio cbr test is one of the most common strength tests. D1557 12 standard test methods for laboratory compaction characteristics of soil using modi. Attempts have been made to apply the dynamic cbr test to. A number in parentheses indicates the year of last. California bearing ratio is the ratio of force per unit area required to penetrate in to a soil mass with a circular plunger of 50mm diameter at the rate of 1. Take the average of three test specimens as the cbr value of the test. Generally there are two methods to design the pavement from cbr california bearing ratio value.
Allow the student to take the test in a smallgroup setting. Field inplace on site cbr tests are used for evaluation and design of flexible pavement components such as base and subbase course and subgrades and for other applications such as unsurfaced roads for which cbr is the. Add water to the specimen and compact it in accordance to standard proctor test or modified proctor test. Proctor mould with a detachable collar assembly and base plate. In modified proctor test, the soil is compacted in the given mold in five 05 layers with a rammer of 10 lbs 4.
Cement modified soil cms is a soilaggregate material that has been treated with a relatively small proportion of portland cement in order to amend its undesirable properties so that they are suitable for use in subgrade or foundation construction. The cbr test may be conducted on a remolded or undisturbed. Modified cbr tests on geosynthetic reinforced soil. This is the most widely used method for the design of flexible pavement. California bearing ratio cbr 62 content 4% above the optimum lime content in case of the weathered soil and were not changed in case of the organic silt see fig. Can one use the dynamic cone penetrometer to predict the. It is known that laboratory and field tests, under saturation conditions, yield different california bearing ratio cbr test values for granular material. The test procedure should be strictly adhered to if a high degree of reproducibility is desired. In the research study presented in this paper, a modified test procedure is proposed to interpret the california bearing ratio cbr test results taking into account the influence of unsaturated conditions in terms of degree of saturation. Astm d188399 standard test method for california bearing ratio of laboratory compacted soil, cbr test. To determine the california bearing ratio by conducting a load penetration test in the laboratory. This test method covers the determination of the california bearing ratio cbr of pavement subgrade, subbase, and basecourse materials from laboratory compacted specimens. Strong correlation between the laboratory dynamic cbr and.
Prediction of cbr using dcp for local subgrade materials. Test method t2 determination of the california bearing ratio of. The modified compaction test first appeared as a construction control in june 1942 5 and has since become known as the modified aashto compaction test. The combined results of their work with deductions therefrom supported by modern research, carried out for the most part after 1950, are referred to later in this paper.
The compaction properties were determined by modified proctor test as per astm d1557. A modified california bearing ratio test for granular. Astm d188399 standard test method for california bearing ratio of laboratory compacted soil. The results obtained by these tests are used with the empirical curves to determine the thickness of pavement and its component layers. The california bearing ratio cbr test has been widely used in pavement design since mid 1940s. D155712e1 standard test methods for laboratory compaction characteristics of soil using modified effort 56,000 ftlbfft3 2,700 knmm3 density water. Ask the student to repeat directions in his or her own words. This paper presents the results of laboratory california bearing ratio cbr tests that were carried out on unreinforced and reinforced soilaggregate systems to. Flexible pavement design by california bearing ratio method.
The californian bearing ratio cbr test is a penetration test used to evaluate the subgrade strength of roads and pavements. The correlation between the cbr and shear strength in. Letakan keping pemberat diatas permukaan benda uji seberat minimal 4,5 kg atau 10 lb atau sesuai dengan perkerasan. Pdf correlation of california bearing ratio cbr value. What is the difference between standard proctor test and. The california bearing ratio cbr is a penetration test for evaluation of the mechanical strength of road sub grades and base courses. In the dry densitymoisture relationship tests, and the california bearing ratio cbr test, sample preparation procedures have been set out in more detail than before, with explanatory flow diagrams. Tests are performed out on natural or compacted soils in water soaked or unsoaked.
Dry density achieved by the modified proctor test is 2720part 7. The cbr correlation curves the design curves are observed correlationships between cbr values and pavement thicknesses. Modified proctor test an overview sciencedirect topics. Cbr testing services and cbr tests site testing services ltd. Soils proficiency testing california bearing ratio cbr laura galbraith. This is due primarily to the higher laboratory strength of the specimen confined in a rigid cylinder. Tests were undertaken on various cbr materials and the bearing capacity bearing value measured at 2. Compaction tests results vary with the input compactive effort, usually measured in foot pounds per cubic foot of soil. An improved california bearing ratio test procedure. The cbr test is tedious, laborious and time consuming. A formula is proposed for determining design values from the modified laboratory data on the basis of theoretical bearing capacity considerations through the theory of plasticity.
Flexible pavement design by california bearing ratio cbr method flexible pavement design by cbr method is used to determine the total thickness of pavement. Cbr is one of the major factors used in pavement design to determine how thick the pavement should be. Standard method of test for the california bearing ratio aashto designation. Cbr test procedure california bearing ratio for road design. Test results are reported and the verification of the suggested method for determining the design cbr value of granular material is shown. The correlations were presented in blowsinchcbr curves from dcp tests, and the bearingcapacitycbr curve from static cone penetration tests.
Astm d1557 12e1 standard test methods for laboratory. Introduction soil compaction is one of the most critical components in the construction of roads, airfields, embankments, and foundations. The cbr test is the california bearing ratio test and site testing services have the experience and knowledge to help you. A soils optimum moisture content is usually lower when compacted to modified proctor versus standard proc. However, standard proctor density criteria is typically utilized in the eastern us where. However, the densities of samples prepared for the cbr test were at considerable variance with those obtained by field equipment, especially for sandy materials of low plasticity. The test was performed by compacting several cbr soil samples using cylindrical molds of 152.