Thermo-chemo-mechanical assessment of support effectiveness during tunneling in squeezing conditions

Large ground deformations characterize the excavation of tunnels in weak rock-masses, often resulting in unacceptable convergence, stability problems, and overstressing of the support elements. These conditions are generally referred to as squeezing conditions. Following the International Society of Rock Mechanics, “squeezing of rock is the timedependent large deformation which occurs around the tunnel and is essentially associated with creep caused by exceeding a limiting shear stress. Deformation may terminate during construction or continue over a long period” (ISRM 1994).