Experimental Research And DEM Simulation Of Loose Sand Under Cyclic Loading

Sand is a common kind of foundation soil. It is necessary to study sand behavior under cyclic loading. Cyclic loading often occurs in engineering, such as traffic engineering, maritime engineering and subway engineering. Essentially, sand's mechanic behavior is controlled by its microstructure, so it is more appropriate to study sand's mechanic behavior and response under both macro and micro respect. For this purpose, laboratory test and DEM(Distinct element method) are applied to research on sand's mechanic behavior under cyclic loading.In this thesis, Large-scale triaxial apparatus is used to carry out static and cyclic loading on loose sand. Accordingly, the creep behavior of sand under cyclic loading was analyzed.Simulation program of cyclic loading was coded based on PFC 2D software and DEM, the main work includes setting up loose sand samples, confirming the porosity of sample, taking use of membrane and testing stress of sand sample in PFC 2D code.In DEM simulations, we pay attention to effect on sand's mechanic behavior from the amplitude of deviational stress, stress level, stress path and sample size. The results were analyzed by comparing DEM simulation and laboratory test .The main conclusions are as following:1. Even under static loading, sand creeps. It is can be concluded that sand's creep expands when amplitude of deviational stress increasing ,both from DEM and laboratory test.2. The sand sample's creep increases with higher stress level.3. If the sand sample was over consolidation, it has different response to test's frequency.4. With bigger size, the sand sample develops less creep.