Elasto-plastic analysis of the surrounding rock mass in circular tunnel using a new numerical model based on generalized nonlinear unified strength theory

Abstract

It is proposed a new numerical model based on the generalized nonlinear unified strength theory (GNUST). Based on the modified continuous multi-segment plastic flow rule, the proposed model considers how confining stresses influence plastic flow on the premise of ensuring the continuity of plastic flow. In a finite-difference code, the proposed numerical model was successfully implemented, and it was validated by simulating the stress distribution in an elastoplastic ring subjected to circumferential pressure in the plane strain state, and the role of the constitutive parameters was investigated. Finally, two rock tunneling projects were analyzed using the proposed numerical model: excavation plastic zone (EPZ) distribution in a deep-buried diversion tunnel and construction displacements in a shallow-buried highway tunnel. The numerical results obtained with the proposed numerical model based on the GNUST criterion agreed well with those from on-site measurements, emphasizing the significance of the intermediate principal stress. The empirical formula for determining the parameter b has been verified by practical engineering, ensuring the application of the numerical model even without triaxial test data. Thus, the proposed numerical model has good applicability to practical rock engineering and can provide guidance and reference for similar rock projects.