DISCONTINUOUS DEFORMATION SIMULATION OF LOESS SEDIMEN-TATION PROCESS AND MICROSTRUCTURE MODEL

Loess is a porous,weakly cemented loose sediments with typical open structure. The mechanical characteristics of loess are typically the macro reflection of its deformation and failure in microstructure. To reveal the mechanical behavior of loess,it is necessary to start from the microstructure of loess since the material composition and microstructure characteristics are controlled by its special aeolian genesis. Based on this,a method to simulate the process of loess deposition and construct its initial structure model is proposed. In order to generate the microstructure model formed by the loess deposition process and simulate the deformation,firstly,the particle group of loess before deposition is generated by Monte Carlo method on the basis of determining the morphology of loess particles. Then the discontinuous deformation analysis method(DDA) is adopted to establish the structure model of loess and to simulate the falling process of loess particles considering the collision force and friction force between particles. From the model,three pore types and four major contact structures can be identified. The consolidation test of the loess initial structure model under different pressures is carried out. The radial distribution function is obtained by selecting particles from different parts. It microscopically illustrates that the macropores and open structures of the loess can be destroyed first during the compression process. The numerical results are compared with the results of physical model test under the same conditions. The results show that the trend of the e-lgp compression curve of the numerical simulation and the physical model test is about the same,indicating that the proposed method is feasible. This method provides a basis for further microscopic analysis of loess mechanical behavior.