Evaluations of Initial Stress and Material Properties of Inhomogeneous Rock Mass by Using Back Analysis on Tunnel Excavation Analysis

摘要

This study discusses the variation of the average Young's modulus arising out of the inhomogeneity of rock mass. Numerical analyses of tunnel excavation in the rock with statistically distributed inhomogeneous materials are carried out. The displacements of extensometer measurements during tunnel excavation on numerical simulation were collected. Back analysis by using extensometer measurements was then carried out. Young's modulus and initial stresses assuming a homogeneous rock mass by back analysis were compared with the average Young's modulus of the original numerical model. It was shown that the inhomogeneity of rock mass affects the area of excavation. The distribution of initial stress and material properties changed from initial parameters of numerical analysis. If the homogeneous size is less than 10% the diameter of tunnel, the inhomogeneous rock mass can be treated as an apparent homogeneous material.