Long-term deformation and control structure of rheological tunnels based on numerical simulation and on-site monitoring

Abstract

The time-varying and creep failure of rocks affect the long-term stability of support structures in deep rheological tunnels. Structure instability is the macroscopic result of damage evolution and strength degradation in microstructures. Hence, the calculation model of long-term deformation and failure of soft rock tunnels is established. The model explains the heterogeneity of rocks by a random local stress field, and explains the local degradation of rocks by an exponential softening law. The effect of stress field distribution on failure mode and long-term instability is revealed. The deformation characteristics of different structure sections are analyzed, and the damage evolution process, failure, and instability properties are further clarified in rock tunnels. The results indicate that the coefficient of lateral pressure determines the long-term creep and damage properties of the surrounding rock, and the rocks show a strong time effect from a large to small deformation rate. The stability of curve shapes is better than that of straight ones in deep tunnels. The shoulder and foot of the structure are always damaged firstly, and continue to evolve in an arc until fracture. A mechanical mechanism is applied to the design of a stable structure, and the control principle of soft rocks is proposed: stress–deformation applicability and space–time applicability. The failure mechanism, control principle, and stability structure “yielding bolt + W steel strip + shotcrete” are demonstrated with the soft rock tunnels of cross mining in Baijiao Coal Mine. Finally, results of this study promote the utilization of soft rock tunnels and provide a new control structure for engineering stability in deep-cross mining.