FEM Analysis For Post-grouting Piles Considering Grouting Process

The bearing capacity of the bore cast-in-place pile is not very reliable because of the influence caused by settlement in the bottom of the pile and mud surrounding the pile. The post-grouting pile combines injecting paste technique with pile foundation technique, which makes cement paste through injected pipe into the pile point and the pile wall under high pressure. It can solve the bad impact of settlement and mud effectively and enhance the ultimate pile bearing capacity largely. At present, the theory about post-grouting technique enhancing pile bearing capacity is not very perfect and the unified construction regulations are not existed. Furthermore, we don't know the mechanism action exactly on how the paste acts on pile point and soil surrouding the pile.In this article, the author adopts three dimensional FEM to study the character of post-grouting pile's bearing capacity. Through imposing initial stress field on simplified model to simulate the influence by post-grouting process acting on the expanded-ending. It builds finite element model to calculate the pile-end bearing capacity of post-grouting piles. And through this method the author obtains the post-grouting piles'bearing capacity with different length and different diameter and draw some contrast conclusions.The main conclusions are as follows:1.when the pile length is equal, the bearing capacity increase extent of different expanded-ending diameter is different. According to the results in this paper, when the pile length is 20 meter, the increase extent of pile-end bearing capacity is from 54.24% to 248.15%.2.when the expanded-ending diameter is equal, the pile-end bearing capacity increase extent of different pile length is different. With pile length increasing, the increase extent of post-grouting pile bearing capacity is different. When pile length changes from 15 meter to 25 meter, the increase extent is from 71.89% to 94.14%. But when pile length changes from 25 meter to 40 meter, the increase extent is from 94.14% to 49.16%.Finally, the author analyzes two practical projects through this method and verifies the rationality and feasibility of this method.