Time Dependence Research On Influence Of Underground Shield Construction On Circumjacent Structures

Shield construction method is one of the main methods of interzone tunnel construction in urban underground. Along with more urban underground lines, there are more and more damages of adjacent ground and structures, and the qualifications of underground tunnel construction is more and more to surrounding structures. The influence of underground shield construction on circumjacent structures is becoming one of the focuses people concern. Geologic environmental effect of many cities'underground space exploit is quite slow, but the tardy deformation may lead to paroxysmal disaster. A number of such accidents happened at home and abroad. So it's necessary to do time dependence research on influence of underground shield construction on circumjacent structures.Numerical analysis method is the most wildly used and mature method, and the most primary means to research the effect of shield construction to ambient structures now. This paper studied the time dependence influence of shield construction to adjacent formation stress field by theoretical analysis, so as to adjacent existing tunnels and buildings by numerical analysis. Firstly, by introducing the fundaments, characteristics and construction process, the reason, mechanism, development process and incidence of ground settlement caused by shield construction were analyzed, and the influence mechanism of shield construction to adjacent existing tunnels and buildings and protective measures on existing structures in contiguity construction were discussed.Secondly, considering the adjacent formation of new tunnel as viscoelastic substance, the relation between adjacent formation stress field and time caused by shield construction was gained by theoretical analysis. Three-dimensional rheologic model was educed by analogy method. By using its rheologic equation, the relations between counterforce of shield tunnel lining, adjacent formation stress field, relative displacement of lining circumference and time were analyzed.Afterward, the time dependence influence of the new tunnel's construction to adjacent existing tunnel was analyzed by numerical simulation method. The new and existing tunnels'planar and three-dimension models were set up with different ubiety and counting parameters of tunnel lining, and the displacement and stress of adjacent existing tunnel at different times after the new tunnel is built are calculated. Taking the displacement and stress increase as safety control indexes of the existing tunnel, the effects of each counting parameter to results was analyzed, and some useful conclusions were educed.Finally, the time dependence influence of the new tunnel's construction to adjacent building was analyzed by numerical simulation method. The new tunnel and adjacent building's planar model is set up. Choosing ground displacement, building inclination and pile foundation displacement at characteristic times as subject investigated, the effects of each counting parameter of new tunnel and adjacent building are analyzed, and some conclusions are educed to consult practical design and construction.