California Bearing Ratio of sub-grade clayey soil under different surcharge weight rings

The upper sub-grade of many countries is manly formed from a clayey soil. This kind of soil presents a weak California Bearing Ratio CBR value when it is soaked. The normal CBR test is done by applying a continuous load after placing surcharge weight ring on the compacted soil. The main purpose of this paper is to study the effect of the vertical confinement caused by the surcharge weight 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 weight ring loading ranging from no ring till four rings. At the same time, identifications tests are performed on these soils in order to identify 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 loadings 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.