Structural Analysis Of Hydraulic Pressure Pipe With Cushion Layer

In penstock of hydropower station, turbine spiral casing, or large water conveyance tunnel project, it's normal to set the cushion layer between internal and external lining, in order to improve the load-carrying proportion of internal lining, reduce internal pressure transfer coefficient and loop tensile stress of external lining, improve the stability and emergency capacity of the overall structure.In previous research and engineering practice, most of the cushion layer considered as linear elastic material, lacking of in-depth study of its nonlinear characteristics. In this paper,commonly used in polyurethane cork cushion material, for example, combined with its material nonlinearity, the hydraulic pressure pipe with cushion layer was studied in the following aspects:(1) This paper based on the structural mechanics method, combined with nonlinear constitutive relationship with residual strain of cushion layer material, logically derived the analytical solution of penstock with cushion layer, bending moment, axial force, shear force, rotation angle, displacement and stress of each section of the penstock among the cushion layer laying range.(2)To study the scope of cushion layer on the structure impact of the penstock structure, this paper through analytical solutions of penstock with cushion layer, compared with different scopes of the laying cushion layer and the results are compared with the linear elasticity. The results showed that:Within the scope of the laying cushion,there are no significant effect on the inner structure of the water pressure transfer coefficient, pipe stress and axial force etc. For the moment and shear pipe laying in the bottom of the cushion layer only slightly changed, but the magnitude is not large.(3) For double decked tunnel with cushion layer (Such as tunnel passing through yellow river in South-to-North Water Diversion Project), now, most of the researches focus on the finite element analysis and lack of analytical solution. By elastic mechanics,the cushion layer is considered as a nonlinear material with known residual strain,for load-transferring mechanism of double decked tunnel within all-inclusive scope cushion layer, the theoretical derivation and analysis, and the analytical solution was obtained.(4) Analysis of the influence parameters in the hydrostatic transmission of the double decked tunnel with cushion layer structure analysis of the effects of the hydrostatic transmission in parameters, now, is not very comprehensive. This paper obtained by analysis of variance:the elastic modulus and the thickness of the cushion have a very large influence on water pressure transfer coefficient of the double decked tunnel with cushion layer structure. Different external earth and water pressure effect on the structure of the main results are obvious. Exterior and interior lining thickness and modulus of elasticity have little impact on the results of calculation.