DEM Simulation Of Active Earth Pressures On Rigid Retaining Wall With Narrow Backfill Space

With the development of the research on earth pressure and the current practice of retaining wall application, we get deeper understanding on limitations of traditional Rankine's and Coulomb's earth pressure theory's assumes. Especially in the design of retaining wall with narrow backfill space, it will cause a large waste if we calculate the earth pressure according to the Rankine's and Coulomb's earth pressure theory. In order to study the active earth pressure on rigid retaining wall, the author simulated the active earth pressure on rigid retaining wall with different backfill space width by using the DEM software PFC2 . In this paper, the rigid retaining wall moved in translation mode and the backfill was sandy soil.Besides, the boundary behind the retaining wall was vertical.On the basis of reasonable parameters of the DEM model, the research object is 5m high rigid retaining wall. And the translational displacement of the retaining wall was 0.005m(?/H=0.001). Firstly a DEM model with 20m backfill width was built to simulate the Rankine's active earth pressure theory, then the backfill space width was gradually decreased.And the backfill width was taken 10m, 5m, 4m, 3m, 2.5m, 2m, 1.5m and 1m respectively. By the contrast of the simulation results of different backfill width models and Rankine's active earth pressure theory, the resultant force of active earth pressure was analyzed. The distribution and the height of resultant of active earth pressure on retaining wall was studied by dividing the retaining wall in average. Considering the aspect ratio of the backfill space, a relationship between the active earth pressure coefficient and the aspect ratio of the backfill space was founded, and the relationship was based on different friction angle between the retaining wall and sandy soil. According to the results of the simulation, the author further studied the active earth pressure on rigid retaining wall under different translational displacement. By taking a reasonable translational velocity of the retaining wall, the changing rule of the active earth pressure on retaining wall with narrow backfill space under the translational displacement was obtained. Using the order of "disp_view" in PFC2 , the active failure wedge in the backfill with different backfill width under active limit state was studied.The results showed that with the decrease of the width of the backfill, the resultant value of active earth pressure also decreases gradually, and the volatility of active earth pressure distribution is also decreasing. Besides, when the backfill sand reached to active limit state,the active failure wedge in the backfill was a inclined plane except the backfill width was 2.5m and 3m, which were close to the distance (2.83m) between the top of the Rankine's active failure wedge at the backfill surface and the retaining wall. That is to say, when the aspect ratio of the backfill space was less than 0.5, the shape of the soil slip crack in the backfill behind the retaining wall was ladder-shaped but not a triangle.