Experimental study and numerical simulation on effectiveness of different capillary barriers in silt low subgrade

In silt low subgrade, capillary effect is an important factor inducing site erosion and collapse, and it is necessary to control the rise of capillary water. In this paper, the effectiveness of eight kinds of capillary barriers formed by geotechnical materials on the vertical migration of water in silt was studied by an indoor model test. Further field tests were carried out to verify the indoor test results. Finally, the vertical deformation of silt roadbed under different schemes was investigated through numerical simulation, and a reasonable scheme was put forward. The results show that among the eight schemes, the four combinations formed by gravel, coarse sand, lime soil layer with 40 cm thickness (curing for 45 days) and lime soil layer with composite geomembrane had the better barrier effect on capillary water, in which the dual capillary barrier using lime soil layer and composite geomembrane had the best effectiveness. The effectiveness of capillary barrier using composite geomembrane and 3% cement soil was the second, and the barrier effect of 5% lime soil cured for 7 days was the worst. The effectiveness of capillary barrier formed by lime soil increased obviously with the increase in age and thickness of lime soil. The numerical simulation results demonstrate that the improved capillary barrier effect reduced the vertical roadbed displacement. The vertical displacement at the center of the embankment was in the following order: lime soil > composite geomembrane > cement soil > coarse sand > gravel.