Investigation of Rock Mass Stability for a Large Tunnel Crossing Faulted Zone: From Mechanical Tests to Numerical Simulation

This paper presents a comprehensive investigation regarding rock mass stability of tunnels excavated in faulted zone. The investigation features a typical Chinese procedure that addresses the support design of large tunnels in difficult grounds. Site survey, mechanical tests, laboratory and field tests were all carried out to determine the mechanical parameters of rock specimen and rock masses at different scales. Such efforts aim to achieve a rational estimate of rock mass mechanical parameters. Then, the design of support measures for such tunnels is discussed. Attempts are made to conduct extensive survey on cases where faulted zones were present during tunnel construction. On basis of these case analyses, design recommendations are put forward regarding the advanced and primary support measures. Then, a three dimensional numerical simulation is performed. The simulation elaborately details the excavation and support procedure during tunnel face advancement and provides a whole process description of rock mass stability. Finally, the rock mass stability is evaluated combining the calculation results and some empirical but sophisticated criterion. The presented investigation work encompasses mechanical test, engineering analogy, and numerical simulation, which are considered major approaches for studying rock engineering problems. The obtained findings, conclusions, and recommendations are hoped to deepen the understanding of mechanical properties of fractured rocks in faulted zone as well as the design philosophy of tunnel support in difficult grounds.