Theoretical Methods For Prediction Of Potential Plastic Zones Induced By Tunneling Under The Influence Of Pile And Box Foundation Loads

With the rapid development of modern cities, traffic problems become increasingly serious. To alleviate the traffic pressure, subway becomes a best choice. When building a subway, due to the constraints of urban space, it is often unavoidable to pass nearby existing structures. In order to ensure the safety of tunnel construction, predicting the surround plastic zone becomes particularly important. Compared with the green field, the plastic zone in the load-bearing ground can be inevitably affected by the foundation loadings. Against pile and box foundation loads, with the introduction of Mindlin soluti-on, this thesis obtained the plastic zone’s boundary equations in load-bearing ground. The contents of the main research and what the result reveals are as follows:(1) Use of the stress solution of Verruijt&Booker and Shan Kou sheng as well as the ideal plastic yield criterion for predicting analytical solution of the plastic zone in green field.(2) For pile and box foundation loads, superimpose Mindlin or integrated Mindlin solution with the solution of Verruijt&Booker or Shan Kou sheng, get the analytical solution of the plastic zone in load-bearing ground.(3) Against the above analytical solution, analysis the influence of plastic zone with different load parameters and different yield criteria.(4) According to the calculation and analysis, conclude the following results:When using the solution of Verruijt&Booker, compared with green field, the plastic zone at the side of foundation load turns larger in the upper part, smaller in the lower part. At the other side of the foundation it performs the opposite. When using the solution of Shan Kou sheng, the variation is just the opposite. Whether use the solution of Verruijt&Booker or Shan Kou sheng, the degree of the influence on the plastic zone can be larger with the increase of the load, smaller with increase of the distance. The plastic zone using the criteria of M-C is larger than the plastic zone using the criteria of D-P.