Numerical Analysis Of Effect Of Underpinning Pile On Excavation Bracing

With the development of our country, the process of urbanize is faster and faster, and the conflict of the rare of land source is standing out day by day. As the exploitation of underground space and the construction of high-rise in urban, a large number of deep foundation excavations have appeared lately. Its scale and depth increase constantly. Urban deep foundation excavations are generally surrounded with dense buildings. So their working space is very narrow, especially when they are close to the foundations of adjacent buildings or structures. The foundations of adjacent buildings or structures do not meet the strength and deformation requirements because of the excavation.Excavation will inevitably encounter the questions, such as protection of surrounding buildings, protection of surrounding pipelines and so on. "Underpinning pile method" is a new method to carry on the excavation bracing in recent years when the building is adjacent to the existing excavation of a foundation pit. Its principle is based on the weight of the building, the soil engineering property, the probable destroy type and extension. Its'guiding ideology is the load transfer and stress transfer theory. The underpinning piles can directly restrict the vertical displacement of adjacent buildings, and underpinning piles and soil nails can bear lateral earth pressure. The underpinning piles and soil nails together attach the purposes of anti-subsidence and anti-lean.The numerical model of a project was built using FLAC3D. The parameters of the model were improved until made sure the feasibility of the simulation. Numerical simulation is carried out with the changing of the size of superstructure loads, the length of the underpinning pile, excavation depth and the mounted depths of the pile, to better understand the effect to the adjacent building, including the horizontal displacement of the underpinning pile, the settlement around the foundation, the horizontal displacement, the leaning and the settlement of the building.