Optimization Study Of Small Net Tunnel Minimum Safe Spacing With Arched Tunnel Wall

We simulate the common excavation methods of little clear distance tunnel respectively ,analyze the stress of support structure and the displacement of mid-adjacent rock of each method ,and recommend the better excavation method to construct little clear distance tunnel in rocks of II .Then we analyze the different clear distances of little clear distance tunnel ,and come up with the minimum safe clear distance to construct little clear distance tunnel in different rock sorts and different depths of embedment, under the circumstance of the model and the parameter of this paper.Then we analyze the common section configurations and stay bearing form of mid-board, and table a proposal of how to choose mid-board .we also study the various dimension and symmetry and asymmetry of mid-board. The Minimum Safe Clear Distance of I , IK IIIrock sort of shallow depths of embedment is 12m, 10m and 6m individually. The Minimum Safe Clear Distance of I, II, III IV , V (including VI)rock sort of deep depths of embedment is 9m. 7m and 4m individually.Then we analyze mid-board of double-arc tunnel, we educe the best section configuration of mid-board. At last we analyze different measurement and excavation method of mid-board we come up recommend measurement and farthest excavation method of mid-board.