1989 年 38 巻 426 号 p. 235-240
In order to determine the optimum shape as well as the optimum excavation and support systems for tunnels, a three dimensional back analysis method based on an optimization technique is developed. Equivalent values of mechanical parameters of rocks surrounding the tunnels are back analyzed, which reflect non-homogeniety of the rocks, stress relief condition and structural conditions such as cracks and joints. Application of the method to an extremely squeezing tunnel shows appropriateness of the method through comparison of analytical and field data. To decrease costs and time in three dimensional back analysis, a convenient method is also proposed, by which the maximum and the minimum principal stresses of the ground and the direction of these stresses in the tunnel cross section are directly determined from convergency data.