Physical Modeling of Lined Tunnel in Squeezing Ground Conditions: Fid-Bau Portal

Physical Modeling of Lined Tunnel in Squeezing Ground Conditions

Arora, Ketan / Gutierrez, Marte / Hedayat, Ahmadreza

In tunnels excavated in squeezing ground conditions, the excess rock pressure may cause failure of the tunnel lining leading to substantial rock deformation. The increase in rock pressure and deformation may be time-dependent, indicating that creep plays an important role. This paper presents a three-dimensional physical model of a lined tunnel subjected to true-triaxial stress state. The model material is a synthetic mudstone prepared by mixing cement, clay, and water in a specific proportion. The model consists of a cubical mudstone specimen with a pre-existing tunnel and lining element. Strain gauges are installed on the lining element as well as embedded around the tunnel. The cubical sample is loaded in a true-triaxial cell at stresses equivalent to the field stress levels. Five acoustic emission sensors are also installed on the surface of a cubical specimen to record and locate any damage in the rock or the lining element. The stresses, deformations, and damages are continuously monitored for several days to study the effect of creep. Results from this experiment show the potential capability of this physical model in understanding and differentiating damage and deformation due to instant stress release and creep behavior of rock around the tunnel boundary.