Numerical Simulation Analysis Of Deformation Of High-Speed Railway Bridge Foundation Overlying Mined-Out Area

Mineral resources are rich and are widely distributed in China. Because of the historical reasons, most of the gobs for mining are abandoned without effective governance. There is a large area of ground subsidence and fissures in the stage of development of the mined-out area, although some mined-out areas have not been clearly changed, they still have a serious threat to the construction and the people’s lives and property. And the mined-out area is one of the potential geological disasters by human activities.In this dissertation, based on the number59pier section of DK499+584.180and the number62pier section of DK499+682.28in GuanShanDi bridge of HeFu railway, the numerical modeling is built by finite difference software FLAC3D, this dissertation studies the regularity of the settlement deformation and the load transfer of the two piers under the influence of the upper load. The main contents and results are as follows:(1) The research status of the numerical simulation method at home and abroad about the deformation of the bridge foundation, the stability and the governance of technology of the goaf is summarized systematically.(2) Analyze the numerical simulation, which shows that the pile foundation under the pier which is through the mined-out area is reinforced to reduce the sharing load in the soil among piles and reduce dramatically the settlement between the stratum and the foundation. Meanwhile, it is inhibiting the settlement of the mined-out area. All above prove this handling method has good reinforcement effect on the bridge foundation in the mined-out area.(3) A numerical simulation has been conducted to study the law of settlement, and the results suggested that sedimentation increases as the load increases. The more shallow location, the greater amount of settlement for soil layers at different depth. There are some differences in the soil among piles and the top of the pile for the pile settlement however it is negligible. The relative displacement of the pile-soil increases as the load increases and the trend has gradually getting gentle.(4) Analyze the load transfer mechanism of two piers, which suggests that the pile axial force reduces from the top of the pile to the bottom of the pile as the load increases, the axial force which is at the top of the pile is maximum and increases with the increment of the load: The axial force remains unchangeable while the pile passes through the gob, because there is no contact with the formation in this section; The pile skin friction increases first and then reduces as the load increases, the figure is zero in this section while the pile passes through the gob. The increase of the pile-soil stress ratio and the pile load sharing ratio shows that the piles begin to take on more loads.