Bearing Capacity Investigation of Silty Sandy Soil Layer Using Kunzelstab Test

This study presents the effect of the 3 apex angles of cone and water levels on the bearing capacity of silty sandy soil (SM) layer by interpreting results from Kunzelstab test. The SM soil layer was prepared in the testing tank and it was used as the representative of sandy soil for some area in Thailand. As the results, the cone angle increase, a number of blows increase and the adjusted factors of the blows from the apex angles of 60° and 180 º to be that of the apex angle of 90º (control) were 1.118 and 0.878, respectively. The obtained correlation between the blows and the internal friction angles of SM soil can be used for calculating the soil bearing capacity which lowers the ground surface of 0.6 m. The soil bearing capacity of SM soil below ground water level decreases 70 to 75 percent (average values from testing results) comparing to that of dry soil. Moreover, the bearing capacity of SM soil above the water level up to 0.6 m decreases 25 to 30 percent (average values from testing results) comparing to that of dry soil at the same depth. Silty sandy soil layer was found determined to have lower bearing capacity due to higher ground water level. Therefore, the calculation of the soil bearing capacity in silty sandy soil layer should be considered the effect of ground water level.