Aiming at coarse-grained backfilled foundation

improvement effect of dynamic compaction has been studied by ABAUQS using geometric nonlinear three-dimensional finite element method. The plastic deformation caused by each tamping has been taken into account and the shape of the plastic zone has been identified after each drop; the parameters of soils in the plastic zone have been adjusted

which makes the base of next impact analysis. The whole process of dynamic compaction is simulated by repeating the steps mentioned above. The developments of plastic zone in different impact energies or in same impact energy but different number of drops have been obtained; and that will be used to forecast the distribution rules of reinforced zone of dynamic compaction effectively. The conclusions give some references for the practice.