Abstract
Strain-softening analyses were performed around a circular bore in a Mohr–Coulomb rock mass subjected to a hydrostatic stress field in cross section and out-of-plane stress along the axis of the bore. Numerical procedures that simplify the strain-softening process in a step manner were employed, and on the basis of the theoretical solutions of the elastic–brittle–plastic (EBP) medium, the strain-softening results of the displacements, stresses and the plastic zones around the circular bore were obtained. The numerical solution was validated based on the fact that the strain-softening process became EBP when the softening slope was very steep and elastic-perfectly plastic (EP) when the softening slope was near zero. The results illustrated that the stresses and displacements in the rock mass surrounding the bore were affected by axial stress and that a proper consideration of out-of-plane stress was necessary. Moreover, the presented results can be used for the verification of numerical codes.
Highlights
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, College of Engineering and Science, University of Chinese Academy of Sciences, Beijing 100049, China
Many analytical solutions are presented while the excavation of circular and spherical cavities is considered in pre-stressed fields
A comparison of the results presented in Figures 13–15 indicates that the dimensionless radial displacement at the bore wall and the normalized plastic radius obtained by the strain-softening model fall between those of the EBP and elastic-perfectly plastic (EP) models
Summary
The internal pressure (pin ) is gradually reduced, and displacement and stresses are only the functions of radius r when gravity is ignored. The medium is elastic and the solution is σr = σ0 − (σ0 − pin )(r0 /r ) σθ = σ0 + (σ0 − pin )(r0 /r ) σz = q u=. Since the problem is axisymmetric, σz , σθ and σr are the three principle stresses. It should be noted that compression stress is taken to be positive in this paper. When the internal pressure continues to decrease, a plastic zone appears around the bore
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