Numerical Simulation Of The Influence Of Shield Tunneling On Surrounding Environment

The shield driving method has been one of the main construction methods in the metro engineering of our country. The surface settlements and influence on surrounding environment caused by shield tunneling are the problems highly concerned in the design and construction process of shield tunnel. This paper using 3D FFM to study the soil displacements, the surface settlements and the influence on the nearly spaced tunnel during shield tunneling. A number of useful conclusions have been gained. The main works of this paper are listed as follows:(1) The main construction aspects, the main factors causing soil displacements and the merits and shortages of the existing FEM simulation methods of shield tunneling have been analyzed, A serial of modified methods were proposed to improvement the shortages of existing simulation methods. A new 3D FEM simulation model which can consider the influence factors more completely and reasonably was proposed.(2) A 3D FEM program was compiled. The program was used to study the rules of soil deformation and surface settlement during shield tunneling.(3) The bearing properties of shield tunnel lining both in the construction stage and in the using stage were studied based on the results of 3D FEM analysis of shield tunneling. The bearing properties of different kinds of linings were compared.(4) The influence factors to the surface settlements such as the depth of overlapped soil, the outer diameter of the shield tunnel, the released stress at the cutting face, the module of the soil and the fill ratio of the shield tail void were studied using the FEM method. A calculation formula which considers most influence factors was proposed. The applicability of the commonly used settlement estimating formula were analyzed based on the observation data, The modification advice was proposed at the same time.(5) The influence of new tunnel on long distance overlapped old tunnel during shield tunneling was simulated using the FEM method. The influence of the net distance between the two tunnels, the relative position and the grouting pressure to the interaction was studied too.