Analytical Theory And Analysis Of The Distinction Zones Of Tunneling In Load-bearing Ground

It is often unavoidable for metro tunnels to pass nearby existing structure foundations. Metro tunneling may disturb the surrounding ground and thus cause nearby structure foundation settlements which may adversely affect safety and serviceability. In order to predict and control metro-tunneling induced structure settlement, it is mandatory to calculate the degree and extent of the disturbance to the ground, especially the specific shape and range of the potential plastic zone caused by tunneling. Current existing theories on tunneling-induced potential plastic zone is based upon the premise that the ground is free from structure foundations, while as a matter of factor, once there in reality exists a structure foundation loading, the shape and range of the tunneling-induced plastic zone may be significantly affected and thus ostensibly different from the one for tunneling in green-field site. Therefore, the main works of this paper are listed as follows:1.Use of analytical solution for predicting the ground settlement induced by tunneling in free soil and Plasticity Yield Criterion get the calculation process of analytical solution for predicting the plastic zone induced by tunneling in free soil. Then study the influence on plastic zone due to tunnel displacement parameter.2.To get the calculation process of analytical solution for predicting the plastic zone induced by tunneling in bearing soil, by superposing Boussinesq or Mindlin solution and the solution for predicting the ground settlement induced by tunneling in free soil. Then study the influence on plastic zone due to different load.3. Through the analysis of plastic area induced by tunnel excavation under different conditions, this article concludes that: by increasing load or decreasing the distance between load and tunnel, the plastic zone induced by runnel excavation will be larger. When the distance between load and tunnel is reduced to a certain value, the plastic zone induced by tunnel excavation and the plastic zone induced by the load will be connected as a result of extended plastic zone. Similarly, when the load is in a certain distance away from the tunnel, by increasing the load, the phenomenon of the connection and extension referred above will also be happened.