California bearing ratio for cohesive soils from quasi static cone tests

Abstract

In the majority of nations, the test most frequently employed to identify flexible pavement layers is the California Bearing Ratio (CBR). To get around the test's high cost, inconvenience, and length, Quasi static cone penetrometer machine was fabricated and used to measure the consistency limits (liquid limit-LL, Plastic limit-PL and Plasticity index-PI), which were used to develop an empirical equation to determine CBR. The soil samples were collected in the Districts of Masaka,Kalungu ,Lwengo and Kyotera. A total of fifty soil samples were gathered and taken to the lab for analysis. To ascertain the CBR in the dry state, soil tests were conducted, Plastic limit,Liquid limit and plasticity index . Quasi static penetration forces at 20mm depth of penetration were determined for all soil samples at moisture content equivalent to plastic and liquid limit. It was found that the a forces of 1020gf and 60gf were achieved at a depth of 20mm when the soil was at state of plastic and liquid limit respectively. The correlation and regression analysis between consistency limits, and the experimental CBR obtained showed relatively good coefficient of determination of R2 = 0.907 between CBR and all the parameters using multiple linear regression analysis (MLRA). The regression equation developed was used together with the relationship developed between the Quasi static Penetration force at consistency limits and the tested consistency limits using thread rolling and cone penetrometer test to come up with the general empirical equation. The empirical equation was validated and found that the CBR values tested using the Quasi static cone penetrometer machine had average variation of 11% compared with those tested using California Bearing ratio equipment