Failure responses of rock tunnel faces during excavation through the fault-fracture zone

Abstract

It is essential to cast light on the construction risks in tunnel excavations through the fault-fracture zone (FFZ). This study adopts the material point method (MPM) to simulate the failure responses of a rock tunnel face during excavation through the FFZ. A numerical study was conducted to compare a physical model test and validate the feasibility of using the MPM in simulating tunnel face failure. One hundred ninety numerical simulation cases were constructed to represent a rock tunnel excavation project with different site configurations. The simulation results suggest that the cohesion and the friction angle significantly influence failure responses. The tunnel cover depth can magnify the failure responses, and the FFZ thickness significantly affects the mobilized rock mass volume when the FFZ consists of a weak rock mass. The numerical simulation results suggest three deformation patterns: face bulge, partial failure, and slide collapse. The failure responses can be characterized by stress arch, slip surface, angle of reposing, and influence range. The insights suggested by the face failure responses during excavation through the FFZ can aid field engineers in determining the scope of possible damage, and in establishing emergency measures to minimize losses if such failure occurs.

Keywords

• Tunnel face failure
• Rock tunnel excavation
• Large deformation
• Fracture fault zone
• Material point method