Research on Influnence Law of Existing pipe-jacking Tunnel affected by Adjacent Foundation Pit Excavation in Soft Clay Stratum

Abstract

The problem that existing pipe-jacking tunnel was disturbed by adjacent foundation pit excavation had arose relative researcher’s attention, especially in soft clay stratum. Firstly, by means of numerical simulation, the deformation of diaphragm wall and settlement law of soil outside the pit during foundation pit construction were analyzed. Then deformation and stress characteristics of existing pipe-jacking tunnels were studied influenced by different spacing between foundation pit and pipe-jacking, different excavation depth of foundation pit and different buried depth of pipe-jacking. The main conclusions were as follows. (1) The maximum horizontal displacement of the diaphragm wall was located at 3/4 of the excavation depth of pit. (2) Due to the blocking or isolation effect of existing rigid pipe-jacking on the deformation of surrounding soil, the surface settlement became smaller.(3) Deformation, structural stress of pipe-jacking would gradually decreased under the conditions of increase of the spacing between foundation pit and pipe-jacking, decrease of excavation depth of pit and buried depth of pipe-jacking, (4) Due to the influence of pit excavation, deformation and stress of pipe-jacking near the end wall and middle of the foundation pit were relatively large. (5) When the buried depth of pipe-jacking was located at near 3/4 of excavation depth of pit and the spacing was less than 10m, excavation of the pit has a great impact on the existing pipe-jacking tunnel.