Research On Behavior Of Pile-group Foundation During Shield Driven Tunneling

It often happens when tunnel is driven underground near pile-foundation in downtown.Effect of tunneling on pile-foundation nearby is vital for engineer.Interaction between tunnel and pile foundation and deformation of pile-group and single pile during tunneling are studied with model test and finite element method,and behavior of pile-group foundation during tunneling is discussed.Behavior of single pile and pile-group during tunneling is studied when number of protection pile and pile length are different with the model test,and the following main conclusions are acquired:the soil within the scope of 2D(D stands for diameter of tunnel)above tunnel has the type "U" settlement trough during tunneling,the shorter the distance between soil and tunnel,the bigger the soil settlement;shielding effect of protection pile reduces the displacement of soil around pile,making the displacement of soil decrease,as a resul,bending moment along pile diminish accordingly.Behavior of single pile and pile-group during tunneling is studied when number of protection pile quantity,axial load,depth of tunnel,distance between pile and tunnel center and pile length are different with the finite element method.For single pile,the following main conclusions of single pile are acquired:protection pile can decrease the settlement of soil during tunneling,the smaller the distance between protection pile and tunnel,the smaller the settlement of soil;when the spacing of protection pile is large,the settlement of soil increase;shielding effect of protection pile reduces the lateral displacement of pile,when the distance between protection pile and tunnel is small.lateral displacement of pile-top decrease;when the spacing of protection pile is large.lateral displacement of pile-top increase.For pile-group,the following main conclusions are acquired:when tunnel is buried deeper,the scope of soil influenced during tunneling is greater,and so does the settlement of soil and at pile top;when the pile lengths on both sides of tunnel are different,settlement of the shorter pile is greater and pile-group tilts to the shorter pile side,pile reduces the displacement of soil around it,compared with short pile,reduction in soil displacement around long pile is greater;when the pile lengths on both sides of tunnel are same,the larger the distance between pile and tunnel,the smaller the pile's positive effect on soil displacement reduction;when the pile lengths are same,distance between tunnel and pile on the left side is 4m,and that on the right side is 8m,settlement of pile on the left side is greater and pile-group tilts to the left side.As a result settlement of soil on the right side is greater.