Numerical Analysis On Characteristics Of Reinforced Soil Retaining Wall Based On Particle Flow Code

The reinforced soil retaining wall(RSRW)was widely used in different kinds of civil engineering,such as highway engineering,railway engineering,water transport engineering,municipal engineering,mines engineering-and so on,and remarkable economic benefits social benefits and environmental benefits were obtained.but in general,the theory of reinforced earth engineering always is behind the practice,and the technology is behind the experience.Besides that,the mechanism of RSRW is extremely complex,there are many researches on macroscopic properties of the RSRW,but few on microscopic characteristics.Based on large scale model test of RSRW of Heyuan-Longchuan Express,particle flow code(PFC)numerical simulations was used to investigate the characteristics of the RSRW,and analyze the characteristics,stress states and destroyed process of the RSRW.The main work is as follows:(1)The rolling resistance linear model(rrlinear)is used as the contact constitutive model of soil mass.The sensibility of micro parameters in rrlinear was analyzed,and the effect of micro parameters on macroscopic mechanical behavior of soil mass was explored.Also,the calibration sequence of micro parameters was proposed.Combined with shear strength index of soil of the RSRW,the micro parameters of filling soil were calibrated by the biaxial numerical test,and the micro parameters,corresponding to the macroscopic mechanical parameters,were obtained.(2)Based on the laboratory large scale model test of the RSRW,the discrete element numerical model of stepped reinforced soil retaining wall had been set up by PFCZD,which was used to simulate the process of loading.The displacement of particles,the stress distribution and the force chains distribution of the stepped RSRW were analyzed by numerical simulation.Compared with model test,it proved that the discrete element numerical model is reasonable.The simulation results show that the geogrid can confine the horizontal displacement of soil and reinforce soil effectively.The geogrid endure the soil pressure of upside and transmits the pressure to surrounding soil,and it improved the distribution of vertical soil pressure of the RSRW.The quantity of strong force chains of reinforced area is more than it at unreinforced part,and it verifies that the geogrid can strengthen the soil.The vertical stress at the back of panel is smaller than it in the reinforced area,which shows that the unloading of the step has greatly influences on the soil behind the panel.(3)The dynamic process of failure of the stepped RSRW is simulated with discrete element method(DEM),it found that the major failure mode of the RSRW is plastic failure.Soil particles have been in plastic flow states when the RSRW was failure without obvious cracks.After the failure occurs,the massive soil particles have fell and accumulated on the steps.The steps have collapsed over time,and the continuous sliding surface have formed in the retaining wall front,the soil particles were heaped in front of panel.The contact force was relatively small and had no strong force chains among the accumulated particles.The strong force chains were cut off in course of retaining wall failure,and the potential fracture plane was formed,which is far from the 0.3H method,but is similar to the potential fracture plane of theoretical calculation of the stepped RSRW.