Abstract：The road from Hailaer to Manzhouli passes through the Hailaer wetlands，where a thin soft soil layer exists on the ground surface. Furthermore，the ground water level is so high that in rainy seasons it rises over the ground surface. The dynamic replacement method(DRM) is chosen to comprehensively consider the feasibility of construction and economic effects. According to the design，some large diameter piles are formed by filling the rammed holes with crushed stones which are acting as the skeleton of the composite foundation. Dynamic compaction replacement is an economical，simple and convenient method for soil improvement，but there is no mature method for design and calculation，so before construction，representative field is often chosen in which field experiments are done in order to confirm applicability and the effects of reinforcement. Firstly，the effect of pile diameter on reinforcement results under a certain replacement ratio is studied using the finite element method. Based on the calculation results of the FE method，the diameter of the pile can be chosen and applied to in-situ construction. Through experimental research of dynamic replacement in the typical field，construction parameters are confirmed，and the rationality of this method used to improve this kind of soil foundation is validated.
