DEFORMATION PREDICTION OF SUBWAY SHIELD TUNNEL DURING EXAVATION WORKS

Abstract

We proposed a simple method that estimate displacement of shield on excavating above shield and verified this method by two results that were measured under different ground structure and different plan of excavation. We get a few opinions by this verify and refer as follows.1) The shield displacement is predictable in two-dimension elasticity FEM analysis that considers the ground rigidity decrease by the excavation in the direction of the axis line and the decrease by the excavation is from initial rigidity obtained from PS logging. The bottom of decrease area should set as bottom of pressure bulb (σ_z=0.1p). 2) Value of shield displacement is estimated as that of ground at bottom of the shield.3) The three-dimensional effect of the excavation plan that have the longer side in the direction of the axis line is estimated multiply α (Ratio of analytical result in direction of axis line of digging center and analytical result in direction of crossing) by the analytical result in the direction of the axis line.4) The shield displacement is estimated by decreasing the ground rigidity the area modeled pressure bulb (σ_z=0.1/p) when the final excavation.