Study on Formation Mechanism of Zonal Disintegration of Surrounding Rock in Deep Tunnel

Abstract

With the construction of underground rock engineering, the surrounding rock in deep tunnels appears zonal disintegration of fracture and intact zones alternate distribution, which is a special engineering geological phenomenon. This study establishes a partitioned fracture model under the coupling of high in-situ stress and osmotic pressure, and identify the key influencing factors of the fracture model. Furthermore, a stress intensity factor (SIF) of initial cracks on surrounding rock elastoplastic boundary is derived using the transformation of complex functions. Considering the high seepage pressure of the surrounding rocks, a zonal fracture initiation criterion is established combined with the analysis of redistributed stress fields. Finally, the obtained criterion is embedded into an extended finite element method (XFEM) platform for numerical simulation. Taking the maximum circumferential tensile stress as a cracking criterion, the propagation trajectory of rock cracks is traced by contour methods. Calculation results have realized the modelling of a whole process of crack initiation, propagation, and formation. And the established criterion has be verified.