Experimental and numerical simulation study on mechanical and engineering properties of silt roadbed under capillary water

Silt has the characteristics of capillary pore development and strong water sensitivity. The rise of capillary water in silt may cause the strength of the roadbed to decrease or instability. It is vital to identify the mechanical and engineering properties of silt roadbed under capillary water. In this paper, a typical silt in Nantong of Jiangsu Province was selected to investigate the variation rules of the cohesion c, the internal friction angle φ, and the compression modulus E_s under different water content by quick direct shear test and compression test. Furthermore, based on the test results, the engineering characteristics of low embankment under capillary water were studied by numerical simulation. The results show that the saturation S_r had little effect on the φ but had an obvious effect on the c. The c of silt decreased with the increase of the S_r. With the increase of water content w, the E_s of silt showed a strong nonlinearity. When the void ratio e was larger, the w was the main factor affecting E_s. However, the experimental results have a certain applicability, that is, the form of water and gas in the silt was in the stage of “internal connectivity of gas phase.” In the case of the same groundwater level, when the filling was low, the deformation of the subgrade was obviously affected by capillary water. According to the simulation results, it is preliminarily determined that the reasonable filling height of silt low embankment was between 1.2 and 1.5 m.