Stress Around a Shaft or Level Excavated in Ground with a Three-Dimensional Stress State

Abstract

The stress around underground openings is much affected by the state of stress in the ground at which the opening is made. The present paper describes the results of an investigation of the stress distributions around a vertical shaft, an inclined shaft and a level, taking into account the fact that the ground is in a three-dimensional stress state. First the stress around a circular inclined shaft is analyzed strictly and it is proved that some components of the stress are indeterminate. Secondly the general method of experimental analysis of stress by means of two-dimensional and three-dimensional photoelastic experiments is discussed, paying special attention to the evaluation of indeterminate stresses. By the method thus obtained, the stress is found around a shaft or level with a square or rectangular cross section having rounded corners, from which the influence of the state of stress in the undisturbed ground upon the stress around a shaft or level is discussed.