Simulation Analysis Of Soil-water Interaction Microscopic Mechanism Of Unsaturated Soil

The researches of unsaturated soil on the macro scale have been obtained plenty of achievements, which formed some systematic theories and a series of testing technologies. Studying the three phase composition of unsaturated soil and interaction of them on the mesoscopic scale provided a new way to reveal the nature of unsaturated soil. However, the existing testing methods and testing technologies could not acquire enough information on the microscopic scales from soil samples. While numerical experiments can overcome the difficulty of testing in soil tests. Based on the theory of capillary water for unsaturated soil mechanics, this paper applied the interaction between capillary water and soil skeleton to Discontinue Deformation Analysis(DDA), and put forward a novel numerical method which could calculate the discontinuous deformation and the interaction between capillary water and soil skeleton. This numerical method is named as DDA-CAP.We had made some assumptions to ensure that the distribution of capillary water was determined solely and could be solved according to the nature of the capillary water in DDA-CAP. First of all, the possible water meniscus between two units can be found by finding intersection of the path lines of the center of the meniscus. Meniscus between two units can be obtained through filtering the unreasonable meniscus. Finally, the multi-units capillary water distribution system can be determined by simplified dealing with intersection meniscus or overlap meniscus on the basis of the capillary water distribution of two units. According to the pictures of capillary water distribution, capillary water volume can be obtained. Furthermore, we utilized the monotonicity of SWCC to calculate meniscus radius and matrix suction. The capillary force was calculated according to the matrix suction and capillary water distribution. The capillary force was added to discontinuous deformation analysis(DDA) as boundary conditions. This is DDA-CAP.An unsaturated soil model with 140 particles which consisted of both clay particles and silt particles was built. A simulation of compression test using the unsaturated soil model and DDA-CAP was carried out. This paper obtained the SWCCs and the ―capillary force depending on matric suction curves‖ at the different stages of the compression test and other data. These data indicated that if the relationship between soil skeleton particles was all point contact, the capillary force had an extreme value with the decrease of moisture content. In addition, if the relationship contain a certain proportion of surface-surface contact, the capillary force would increase with the decrease of moisture content. Comparing the SWCCs and the change of the soil skeleton model at different stages of the compression test, we can indicate that void ratio and the property of pores had a huge influence on SWCC. These data and conclusions also indicated that the application of DDA-CAP for the simulation of soil-water interaction was feasible.