Deformation Analysis of Rock Mass During the Excavation of a New Tunnel

With the increasing planning and construction of new tunnel routes near existing tunnels, safety hazards and construction problems are receiving increasing attention. To observe the deformation characteristics within the rock mass more intuitively, this paper adopts a transparent rock model test device to carry out the model test of tunnel-proximity excavation. The transparent rock is an artificial transparent material formulated by mixing silica gel powder, n-tridecane, and liquid paraffin. The impacts of the new tunnel on an existing tunnel are investigated, in which the thickness of the intervening rock layer and the excavation footage are the main influencing factors. Results show that when the new tunnel passes over the existing tunnel, heave deformation occurs in the rock mass around the existing tunnel. When it passes under the existing tunnel, the existing tunnel is deformed by settlement. The maximum deformation of the rock mass around the existing tunnel is located at the center of the existing tunnel, and the deformation trough conforms well to a Gaussian distribution curve, with coefficients of determination (R2) of 0.93–0.98. As the excavation footage increases and the thickness of the intervening rock layer decreases, the deformation of the existing tunnel’s rock mass will increase.