The Safety Analysis On The Supporting Structure Of The Longtian Small Interval Tunnel

Small clearance tunnel is a tunnel form between separated tunnel and multi-arch tunnel. It is much easier to construct, waterproof and control the cost. This paper is based on the Longlin-Baise Tunnel in Longlin-Baise highway, a back analysis on the surrounding rock is performed, and the parameter is obtained. In this paper, a method of the physical parameter on the surrounding rock is researched, and the construction process is numerical analyzed.For the new austrian tunnelling method tunnel construction,the monitoring and measuring on the displacement of the tunnel is a key part of the tunneling. The data directly show the influence on the stability of the surrounding rock by the tunneling behavior during the tunneling. In order to seek out the mechanical parameters matching the reality, back analysis on the monitoring data is performed, which also provide fundamental material to the theoretical analysis and numerical stimulation.To minimum to mutual influence between the two caves, tunneling gap is set to make the distance is at safety, which make the first tunnel and the second tunnel is the extravagated procedure. During the 3D numerical stimulation, the mutual influence between the surrounding rock and supporting structure in the first tunnel and the second tunnel is analyzed. The result shows that the first tunnel influenced the second tunnel more than the the second tunnel influenced the first tunnel。Considering the loose load and the water pressure , a load-structure calculating model on the secondary supporting structure is built. The stability of the opening of the maximum and maxima section 30 meters beneath the surface is analyzed.The water pressure is adverse to the inner force of the walls in the supporting structure, but benefit to the change of inner force in vault and invert.