Abstract: The dynamic compaction method is a soil improvement method that lifting a heavy rammer to a certain height, then falls freely, compacting the soil through the contact of the rammer to produce a huge impact force, to improve soils. This method has the characteristics of simple operation, short construction period, simple technology, etc., and it has been widely used domestically as well as abroad. To further study the effect of the dynamic compaction on the soil, a finite element software was used to simulate the construction process of dynamic compaction. Considering the relationship between the compaction rammer and the elastic-plastic constitutive structure of the target soil, the regional changes of vertical displacement, dynamic stress, velocity and soil plasticity were analyzed under different compaction energy. The results are as follows: (1) Under the impact load, the elastic-plastic deformation of the soil mass occurs. The plastic deformation of the soil mass is mainly diffused from the rammer downward at a certain angle, and the distribution is apple-shaped. With the increase of the ramming times, the plastic deformation area also increases gradually. (2) The vertical displacement and dynamic stress in the soil gradually decrease with depth and show an elliptic distribution in space; (3) With the increase of tamping energy, the soil reinforcement effect is better.

Key words: Dynamic Compaction Method, Large Deformation, Dynamic Stress, Plastic Region, Peak Particle Velocity