Analysis on In-situ Direct Shear Test Results of Unsaturated Silty Sand in the Eastern Part of Beijing

For the typical unsaturated silty sand layer in the eastern part of Beijing, in-situ direct shear tests were conducted, and the cohesion and internal friction angle were obtained by the least squares method. The internal friction angle values are increased by 11.11%~24.4% compared to traditional regional empirical values, and by 3.01%~17.4% compared to the values from the indoor direct shear test. The cohesive force of the silty sand layer measured by the indoor direct shear test is 4.8~7.5 kPa, while the value measured by the in-situ direct shear test is up to 9.5 kPa. The research results provide experimental support for the optimization of the shear index parameters of the unsaturated sand layer in this area, save the cost of foundation pit support, and provide the possibility for realizing green construction in the whole process of engineering construction.