Boundary Value Method For Structural Calculation Of Hydraulic High Pressure Tunnel Linings

With the development of China’s infrastructure construction, the construction and development of hydraulic tunnels and other large underground structures have been accelerated, especially the high pressure hydraulic tunnels, which have already been applied in many projects at home. Since the excavation of the tunnel, the design methods of tunnels based on lining structure have been more mature through the development. At present, there are two main kinds of methods, structural mechanics method and elastic mechanics method.With the rapid development of computer, the numerical solution of structural mechanics method——the boundary value method, arises at the historic moment, which is widely adopted by many researchers and designers because of the advantages of programmable, high efficiency and convenient of it.First of all, this article details the calculation principle of the boundary value method. The important technical processing methods of the program are introduced in detail, and the flow chart of the calculation program is drawn. The calculation program is compiled by MATLAB. The reliability and accuracy of the program are verified by comparing with the calculation results of the LiZheng 5.6.But the boundary value method also has its disadvantages, such as without consideration of the crack of reinforced concrete and water seepage of lining, which lead partial large calculation of high pressure hydraulic tunnel. The reinforced concrete lining cracks and disconnects with surrounding rock under the high water pressure generally. Surrounding rock also assumed the part of the water load. On the one hand this paper reduces elastic modulus of concrete, on the other hand the boundary value method and volume theory of water load will be considered together, and thus the lining will be seen as permeable structure, and the internal water pressure is considered as osmotic pressure acting on the lining and surrounding rock. The paper tries to improve the boundary value method in the above two ways, and the calculation program is compiled for the practical example.Secondly, Considering the actual situation of lining cracking and separation of lining and surrounding rock at very low head, the paper calculates bearing ratio of surrounding rock with different lining thickness, inner radius of lining, permeability coefficient of rock, bar spacing and internal water pressure based on the reinforced concrete lining cracking and disconnect with surrounding rock in the case of circular hydraulic pressure tunnel. Then it discusses the change rule and range of bearing ratio of surrounding rock with above 5 variables based on the data of calculation.At last, the paper summarizes the main contents and prospects the future research.