| Hydraulic tunnel plug,as one of the main control conditions of Water Resources and Hydropower Engineering,although the amount of plug works is very small,but the schedule requirements are urgent.Besides,plugs are closely related to the safety and benefits of Water Resources and Hydropower Engineering,so its design level should be the same as the corresponding hydraulic building and it’s important to ensure its stability and safety.Therefore,this paper relies on the Chongqing Education Committee(KJ1500527)— study on reliability and back analysis method of mechanical performance of hydraulic tunnel plug.Based on the existing traditional setting calculation method,the reliability theory is introduced into the design calculation of the hydraulic tunnel plug,through the analysis of the reliability of the plug,the parameters of the plug are reasonably optimized.The main research contents and achievements are as follows:1.Based on the analysis of current design and Stability calculation method of hydraulic tunnel plug,the development and application of reliability theory are summarized,and the basic research status and progress of reliability calculation method are analyzed.2.Several limit state equations of hydraulic tunnel plug is established by the mechanical analysis of plug.Finally,the reliability analysis of the plug is carried out with the anti-slip limit condition,and the implicit expression of the performance function describing the reliability of the plug is obtained.The three-dimensional finite element model of plug and surrounding rock is established by ABAQUS.The cohesive force C,friction angle φ and elastic modulus E of the surrounding rock are taken as the basic random variables.The friction between the plug and the surrounding rock is obtained by the single factor analysis,and the functional relation is fitted,and then the multivariate regression analysis is carried out to obtain the function relation between the friction force and these random variables,and finally established the explicit expression of the performance function.3.According to the finite element calculation results,analyzed the sensitivity of the friction between plug and surrounding rock to the cohesion,internal friction angle and elastic modulus of the surrounding rock,The results show that when C increases,the contact surface friction decreases and decreases faster and faster,and when φ andE increases,the friction of the contact surface increases and increases more slowly.In the three factors,the friction is more sensitive to the internal friction angle.4.Some commonly used reliability calculation methods are compared and analyzed,with the obtained performance function and the probability distribution type of the basic random variables and the principle of design calculation point method,the Matlab program is designed to calculate the reliability index and failure probability of the plug.5.Through the establishment of finite length models of different length plugs and reliability analysis,respectively,obtained their reliable indicators: 4.15,5.04,5.7,5.9.Then,for each length of the plug to take the mean of random variables and perform finite element calculation and stability analysis,and finally the safety factor K is 2.3,2.86,3.41 and 3.95 respectively.According to the target reliability index of the ultimate state design of the bearing capacity of the engineering structure in China and the safety factor of the plug in the Design Code of the Concrete Gravity Dam,the appropriate design parameter of the plug is 20 m. |
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