The Stress And Deformation Analysis Of Closely Spaced Tunnel With Shallow Depth, Partial Pressed And Altitude Differences

Due to complicated topographical and geological conditions as well as large numbers of mountainous areas, especially in Yunnan province with 94% of mountain areas, constructions of high-grade highway unavoidably meet with lots of tunnel works. Most of tunnels have complicated cross section and shallow depth when constructed in canyon zone. As the shallow depth and poor geological conditions, the surrounding rocks are always soft, fragmentized or intensively disintegrated rock mass with partial pressure. It is an important project problem to consider the advantage, feasibility and construction features of closely spaced tunnel under this kind of condition. This dissertation concentrates on the stress and deformation response to excavation sequence, net distance, altitude difference, partial pressed angle of closely spaced tunnel. The study work is based on the design and construction issues of Pingnian tunnel in Luo-Fu highway of Yunnan province. The contents and methods of study were as follows:1. Based on the closely spaced tunnel Pingnian in Yunnan province, the dissertation calculates three main cross sections with plane FEM software. The class of surrounding rock in the three cross section is mainly V or IV, and the smallest built depth is only 47 meters, and the ground surface is gradient surface. The rational excavation sequences are got under the condition.2. In this dissertation, the excavation sequence, altitude difference, net distance, partial pressed angle and built depth are taken into account to analyse the detailed effect to the closely spaced tunnels. When the altitudes are separately 0, 2, 4, 6 or 8 meters, and the net distance are separately 0.8D, 1.0D, 1.2D, 1.4D, 1.6D, 2.0D, 2.4D or 2.8D(D equals to diameter of tunnel), and the partial angle are separately 10°, 15°, 25° or 30°, the stability influence study of excavating sequences are complicated under V class surrounding rock condition.3. The feasibility of the method is well confirmed by analyzing the relevant model experiment and in-site measurement data.