California bearing ratio cbr test results. The californian bearing ratio cbr test is a penetration test used to evaluate the subgrade strength of roads and pavements. The ratio of the cbr value of the lime fly ash and limefly ash stabilized soil to that of the untreated compacted soil is known as the cbr gain factor. This is the most widely used method for the design of flexible pavement.
The following table gives the standard loads adopted for different penetrations for the standard material with a cbr. For soils with bigger particles other types of bearing capacity can be used like the plate bearing test. The california bearing ratio test is penetration test meant for the evaluation of subgrade strength of roads and pavements.
The results obtained by these tests are used with the empirical curves to determine the thickness of pavement and its component layers. The ratio is usually determined for penetration of 25 and 5 mm. California bearing ratio cbr62 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.
When the ratio of 5 mm is consistently higher than that at 25 mm the ratio of 5 mm is used. California bearing ratio cbr the ratio of the force per unit area required to penetrate a soil mass with a circular plunger of 50 mm diameter at the rate of 125 mm min to that required for corresponding penetration of a standard material. The california bearing ratio cbr is the most utilised parameter for dimensioning flexible pavements in tropical countries.
They can be considered as small scale bearing tests in which the ratio of penetration to the size of the loaded area is much greater than in bearing tests. A cbr value of 2 is usually found for clay high quality sub base will have cbr values between 80 and 100 and some sands may have values around 10. The results of these tests are used with the curves to determine the thickness of pavement and its component layers.
The test is an empirical test which gives an indication of the shear strength of a soil. The cbr test is one of the most commonly used methods to evaluate the strength of a sub grade soil sub base and base course material for design of thickness for highways and airfield pavement. The ratio is usually determined for penetrations of 25 and 5 mm.
California bearing ratio and dynamic cone penetrometer 51 california bearing ratio cbr test 511 introduction 5111 general. The great value of this test is that it is comparatively easy to perform and.
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