| Because of the complexity of the environment and rock mass medium,the deep tunnel engineering is not only affected by the ground stress and groundwater,but also has a strong disturbance effect in the process of construction and excavation.The structural safety design method based on deterministic analysis is often difficult to fully and reasonably reflect the complexity of soft rock tunnel engineering;the traditional reliability calculation theory can not give an explicit expression in theory for the real function of underground structure composed of surrounding rock and support system,which restricts the application of reliability calculation theory in Tunnel Engineering.Moreover,the existing time-varying reliability analysis method ignores the time effect of load and structural resistance in the process of construction and operation.The change of load and structural resistance with time objectively affects the safety of deep buried tunnel engineering.In this paper,based on the reliability theory of Xianglushan tunnel and mathematical statistics,the uniform design method,response surface method and finite element numerical simulation method are combined,with the help of the code for design of hydraulic tunnels(SL In 279-2016),the bearing capacity limit state function of lining structure is constructed,and the explicit expression of load response surface of collaborative bearing of surrounding rock and lining structure is constructed.Thus,a reliability evaluation method of collaborative bearing of surrounding rock and lining structure of deep buried tunnel is proposed,and the single factor random variables affecting the combined bearing characteristics are analyzed,and the possibility of collaborative bearing of surrounding rock and lining structure is identified According to the main factors of reliability,and the load release effect of surrounding rock and the attenuation effect of concrete strength with time,the time-varying reliability analysis method of the collaborative bearing of surrounding rock tunnel lining structure in the construction period and operation period is established respectively,so as to establish a set of safety evaluation method of deep buried hydraulic tunnel.The specific research work and relevant conclusions are as follows:1)Based on the reliability theory with mathematical statistics as the core,the uniform design response surface finite element reliability analysis method is proposed by combining the uniform design method,response surface method and finite element numerical simulation method.On this basis,according to the release effect of surrounding rock load caused bysurrounding rock excavation disturbance during the construction period,a time-varying reliability analysis method for the collaborative bearing of surrounding rock lining structure during the construction period is established;according to the decay of compressive strength of concrete material with time,a time-varying reliability analysis method for the operation period after the completion of tunnel construction is established,which combines the above three methods to form a whole The safety evaluation method of deep buried hydraulic tunnel;2)The three-dimensional finite element numerical calculation model of the coordinated bearing capacity of the surrounding rock lining structure of the hydraulic tunnel with continuous medium is established to simulate the cyclic advance of the surrounding rock excavation and lining construction in the drilling blasting excavation.The influences of the buried depth,the second lining construction time and the external water load on the collaborative bearing capacity characteristics of the surrounding rock lining structure are calculated and analyzed respectively.The related parameters of the surrounding rock and the second lining are further studied The influence of each parameter on the bearing capacity of surrounding rock lining structure is identified,and the random variables needed to fit the response surface function are determined;3)Based on the drilling and blasting method of Xianglushan tunnel,the reliability of uniform design finite element response surface is realized,The whole process of time-varying reliability calculation is analyzed,and the sensitivity of reliability index to coefficient of variation of each parameter is analyzed.In the calculation of time-varying reliability,the rule of time-varying variation of the maximum axial stress in lining structure with the construction process under the effect of surrounding rock load release is established,and the function of time-varying reliability index and time-varying failure probability in this period is fitted;through the decay of concrete compressive strength with time,the time-varying reliability index and time-varying failure probability in the long term after the completion of the tunnel are fitted function4)In this paper,the safety of Xianglushan tunnel under different working conditions of drilling and blasting method is analyzed,and the time-varying reliability variation rules under different burial depth,different secondary lining support timing and different external water load conditions are obtained respectively,and the influence of each working condition on the safety of Xianglushan deep buried hydraulic tunnel is analyzed and compared. |
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