Abstract
The elastoplastic analysis of the surrounding rock of a circular tunnel is a very classic rock and soil mechanics problem. Previous scholars usually studied the situation under axisymmetric load, and they usually did not take the non-axisymmetric load distribution under the influence of ground stress and lateral pressure into account, which greatly affected its application in engineering practice. Approximate analytical solutions for calculating the plastic zone range, stress field and displacement field of the surrounding rock of a circular tunnel are inseparable from the consideration of the strength reduction and volumetric dilatancy characteristics of the rock material. The elastic-softening-residual plastic triple linear stress-strain model and the Mohr-Coulumb failure criterion are involved. The approximate analytical solutions of the residual stress field, strain field, displacement field and radius of the plastic zone in the elastic zone, plastic softening zone and surrounding plastic zone of the circular tunnel surrounding rock under axisymmetric load are deduced. The analytical solutions are valid only when the plastic zone is large and the lateral pressure coefficients 1≤λ<3. The approximate analytical method is close to the calculation result of finite element method and can replace the finite element method to carry out simple elastic-plastic analysis of surrounding rock.
Highlights
The elastoplastic analysis of the surrounding rock of a circular tunnel is a classic rock and soil mechanics problem, which was put forward by R
Most of the existing analytical methods for elastic-plastic analysis of surrounding rock of circular tunnel are based on axisymmetric load distribution, the non axisymmetric load distribution under the influence of in-situ stress and lateral pressure is not well considered, which affects its application in engineering practice
Theoretical analysis and engineering practice show that the strain softening and dilatancy characteristics of geotechnical materials have a significant impact on the mechanical properties of surrounding rock
Summary
The elastoplastic analysis of the surrounding rock of a circular tunnel is a classic rock and soil mechanics problem, which was put forward by R. Lu found an analytical solution to determine the plastic zone near a circular tunnel under non-axisymmetric stress based on the conformal transformation method of complex variable functions, but did not consider the strain softening phenomenon when the rock mass yielded [15]. Taking into account the influence of the lateral pressure coefficient of the in-situ stress on the plastic zone, stress field and displacement field of the surrounding rock, based on the trilinear stress-strain softening model, the Mohr-Coulomb yield criterion is used to derive approximate analytical solutions of the surrounding rock of a circular tunnel’s stress field, strain field, displacement field and radius of plastic zone under non-axisymmetric load in this paper.
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