Abstract:

The supporting effect of pipe roof in Lanjiayan extralong soft rock highway tunnel should be guaranteed. Hence, the influence of pipe roof layout range on stability of surrounding rock of soft rock tunnel is studied by numerical simulation and model test. The study results show that: (1) With the increase of the layout range of pipe roof, the settlement of tunnel crown decreases approximately monotonously, and the ultimate convergence of arch feet shows a nonlinear decreasing trend when other parameters of pipe roof remain unchanged. (2) When the layout range of pipe roof is increased from 90° to 180°, the final crown settlement decreases from -0.389 m to -0.317 m, with a reduction rate of 18.5%, while the final convergence of arch feet decreases from -0.486 m to -0.355 m, with a reduction rate of 26.9%. (3) By enlarging the layout range of pipe roof, the deformation of surrounding rock can be effectively controlled and the supporting effect of pipe roof can be improved; the influence of changing the layout range of pipe roof on the convergence of arch feet is greater than that of the crown settlement. By comparing and analyzing the numerical simulation and model test results under different pipe roof layout conditions, the conclusion that deformation laws of rock around the tunnel obtained by the two methods coincide with each other, and the values of deformation around the tunnel obtained by the two methods under different working conditions are close to each other can be drawn.

Key words: soft rock tunnel, pipe roof, surrounding rock stability, numerical simulation, model test