Numerical analysis of effect of underpinning pile on excavation bracing

"Underpinning pile method" is a new technique 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 weight of the building,soil engineering property,probable destruction type and extension and its guiding theory is load transfer and stress transfer theory.The underpinning piles could directly restrict the vertical displacement of adjacent buildings and bear lateral earth pressure.The piles and soil nails together attach the purposes of anti-subsidence and anti-leaning.FLAC(fast lagrangian analysis of continua)simulation is used to study the effect of underpinning pile method on the stress and the deformation of underpinning piles.Through finite-difference analysis,it is found that the main factors are the size of superstructure loads,the length of the underpinning pile,excavation depth and the mounted depths of the pile.