Research On Influence To Bearing Performance Of Adjacent Pile Foundation By Pit Excavation

With the rapid development of the urbanization, the underground space has got more and more development and utilization and foundation pit engineering has been one of the major subjects of geotechnical engineering in city construction. When we excavate foundation pit in the central area of a city with serried buildings, the bearing performance of adjacent building’s pile foundation will be inevitable influenced in some ways. As a form of deep foundation, pile foundation relies mainly on pile side resistance and tip resistance to transmit load to the soil. Pit excavation will inevitably cause sides way and settlement in the soil. The deformation of soil will affect pile side resistance and tip resistance, and then makes a influence on the bearing performance of adjacent building’s pile foundation. How to forecast and analysis the influence on pile foundation of adjacent building’s by pit excavation has been a hot topic in the field of geotechnical engineering.This paper theoretically analyses soil’s deformation caused by pit excavation and the impact on adjacent building’s pile foundation due to the deformation. Then, this text, using finite element software, establishes three dimensional numerical models for foundation pit and pile foundation of adjacent building and analysises the impact on the pile foundation of existing building in the process of pit excavation under the condition of single-pile column foundation and multi-pile-column foundation. And we can analysis how the excavation depth and the distance between the pile and foundation pit affect the result of numerical simulation. We can get the following results:(1) Through the numerical simulation of single-pile column foundation and multi-pile column foundation, we can find that, with increase of the depth of pit excavation and decrease of the distance between pile and foundation pit, the influence on the pile foundation of adjacent building will be greater.(2) In the numerical simulation of multi-pile column foundation, when the excavation depth and distance between the pile and foundation pit both are invariant, comparing and axial force, pile side resistance, bending moment and deformation of piles in both lines, we can come to the conclusion that the effect by pit excavation on the piles in the line which is closer to the foundation pit is a little greater than lines which is further, but the difference is very small.(3) Based on the results of numerical simulation of single-pile column foundation and multi-pile column foundation, we can discover that the impact on pile foundation by pit excavation is mainly embodied in the additional bending moment and deformation, and the change of axial force and pile side resistance is very small.