The change of rock mass pressure of Lianchengshan tunnel

Based on Lianchengshan tunnel, the changing of rock mass pressure with deformation, time and distance from the excavation face is analyzed by means of field monitoring and numerical simulation, and the main conclusions are as follows: (1) When the deformation increases rapidly, the rock mass pressure decreases first and then increases. After the settlement and clearance convergence are stable, the pressure of rock mass in each part is still increasing slowly. (2) The rock mass pressure is mostly between 0.1 and 0.3 MPa, and the variation lasts about 65 to 70 days. (3) During the period from mid-bench construction to inverted arch construction, the variation ratio of rock mass pressure is very high, which indicates that the stabilization time of this stage is too long. Therefore, it is suggested to shorten the length of mid-bench and lower-bench appropriately. (4) The space influence range of the excavation face propulsion is about 2.5 times the tunnel diameter of the hole (42 m). To decrease the rock mass pressure, ring closure should be reached as soon as possible. It is recommended to speed up the construction of middle bench and lower bench.