Three-Dimensional Numerical Simulation Study On The Soil Distortion Of Shield Tunneling In Loess Area

With the development of economy and city construction, it is very popular to build the metro running tunnels by EPB method. The shield driving method has been one of the main construction methods in the urban tunnel in our country. The soil sedimentations 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 and the surface sedimentations during shield tunneling. It is the first time that builded tunnel in the loess area. So it is usefuled and practicaled to Xi'an tunnel's construction in the future that studied the soil sedimentations.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. The new 3D FEM model that can consider the influence factors more completely and reasonably was proposed.2 EPB method has been broadly used in glutinous, sand and grit layers. Analyzed on the tunnels that used EPB method in different soils, the more logical three-dimensional finite element model is based, which can reality represented the soil transfiguration.3 Due to the engineering example, a 3D FEM simulation model was founded. The model was used to study the rules of soil deformation and surface settlement during shield tunneling.4 The characteristics of loess include the module, conglutination force and inner friction angle of the loess, affected the soil deformation.5 The influence factors to the surface settlements such as the depth of soil, the outer diameter of the shield tunnel, the released stress at the cutting face, the fill ratio of the shield tail void, pouring-slurry press, thrusts and lengths of shield and digging steps were studied using the FEM method. References is brought forward in the loess areas of Xi'an was proposed.