Stablity Study On Massive Excavation To Deep And Large Foundation Pit

As the design alteration in the construction of the excavation project,the problem of large scale overexcavation at the bottom of the foundation pit arises once the excavation and supporting structure has been completed.Distinguishing from the foundation "pit-in-pit",internal force value brought about by large scale overexcavation exceeds that in the original pit maintenance scheme,which has great impact on the overall safety and stability of the foundation pit.The overexcavation will give rise to deformation of the supporting pile and the adjacent soil beyond anticipation.Displacement of the pile body and soil settlement will increase the risk of the collapse of foundation pit.In the research of the effects of the large scale overexcavation on deformation of supporting pile,it still lacks available project cases and theretical support.This paper takes the large scale overexcavation in ShenYang as reasearch backgroud,and analyses the actual project situtation by employing the numerical simulation software of FLAC3D.On the basis of the numerical simulation,the pattern of the effects of large scale overexcavation on deformation of supporting pile will be analysed and the role that different factors played in the overexcavation will be found,among which the patterns of three main factors--diffferent strengthening modes,depth of the overexcavation and different location of the overexcavation--on deformation of the foundation pit will be anlysed.Through the comparison of the deformation patterns under different circumstances,results obtained that under the overexvacation situation,the foundation pit tends to slide in large scope,the largest horizontal displacement locates in the soil under the foundation pit.The depth of the overexcavation has more significant impact on supporting pile among the several factors.When the depth reaches 22m,the horizontal displacement of the foundation pit fencing structures got rapid expansion and difficult to maintain.On the basis of the simulation analysis,this paper summarizes the issue of stability under the circumstances of large scale overexcavation and by combining the actual cases in engineering,illustrates the main factors that affect stability under the cases of overexcavation as well as the influences of different factors.