Dynamic response analysis of a large-diameter steel tube pile group subjected to hammering loads

A large-diameter steel tube pile is used in a machinery factory in Shanghai to test the new produced diesel pile hammer. However, with the increase of the diesel hammer weight, it fails to meet the test requirements and a pile group is recommended to bear the hammering loads with the help of 8 added short piles. But so far, few people have investigated the displacement and load distribution of combined pile groups subjected to hammering loads. To reasonably design the reinforcement type of the pile group, the finite element method is used to study its dynamic responses. Firstly, a three-dimensional single pile model is established and verified through static load tests. The dynamic responses of the pile group are then simulated to evaluate the effects of the mass and depth of pile cap, the length of short piles on its settlement and load distribution. The results show that the maximum compressive stress of corner piles and edge piles are larger than that at the top of the main pile during the impact of hammering loads. For a shallower pile cap, the stress of the main pile head tends to be larger while the settlement of the main pile is smaller. Additionally, the mass of pile cap and the length of short piles have little effects on the dynamic properties of the pile group.