Re-profiling response of heavily squeezed tunnels via ground reaction curves

This paper presents a simple method for determining the re-profiling response of a heavily squeezed tunnel using ground reaction curves. The ground reaction curve of certain tunnel is unique since the mechanical behavior of the original surrounding rock of each re-profiled tunnel remains the same. The dimensionless stress distribution also remains the same for a same support pressure. According to the corresponding relation of material points in the origin and current coordinates, the excavation radius of the re-profiled tunnel is determined. The location of re-profiled tunnel on the ground reaction curve and evolution curves of softening and residual radii can be determined, and the tunnel response induced by the decreasing support pressure can be further predicted using the above three curves. The critical excavation radius for a desired clearance and its corresponding plastic and residual radii can be theoretically determined. As the increase of re-profiling times and/or critical plastic shear strain, the increments of tunnel wall displacement, plastic and residual radii gradually decrease for a constant re-profiling radius.