Effect of soil loading surcharge on its CBR value

Abstract

The upper subgrade of many countries is manly formed from a clayey soil. This kind of soil presents a weak California Bearing Ratio value when it is soaked. Scientists around the world always try to find a way to solve this problem, because it causes cracks and holes on highways. The normal CBR test is done by applying a continuous load after placing surcharge weight ring on the soil. The main purpose of this paper is to study the effect of vertical confinement caused by the surcharge ring on the soaked CBR of soil. For this purpose, five CBR tests are performed to each of the ten different soils collected from Lebanese territories. Each CBR test is performed with different ring loading ranging from no ring till four rings. At the same time, identifications tests are performed on these soils in order to classify them. The CBR test results are linked to the soil properties obtained from the identification tests. The analysis shows that the vertical confinement has a positive effect on the soaked CBR of clayey soils. In general, the CBR value increases as the number of ring loading increases. The synthesis of experimental results shows that the increment ratio of CBR for soil under a given number of rings is related to the liquid limit of the soil.