Research On Fuzzy Reliability Of Surrounding Rock Stability Of Hydraulic Tunnel Supported By Shotcrete

The stability of the surrounding rock of hydraulic tunnels is one of the key issues of concern in the field of underground structures in hydropower projects.In engineering,deterministic methods are usually used for analysis and evaluation,such as engineering geological analogy,analytical methods,and numerical analysis methods.Due to the numerous factors that affect the stability of the surrounding rock of the tunnel,there are uncertainties.The traditional deterministic calculation method has certain limitations,and the consideration of the stability,safety and reliability of surrounding rock is not comprehensive enough.Therefore,based on the theory of structural reliability,this paper takes the spray-anchor supporting hydraulic tunnel as the research object,and uses the elastoplastic mechanics analytical method to construct the functional function.Considering the randomness and ambiguity of physical and mechanical variables and the ambiguity of failure criteria,the reliability of the tunnel is quantitatively analyzed.The main research contents are as follows:(1)Based on the interaction principle between the surrounding rock and the supporting structure,the elasto-plastic mechanics analytical method is used to establish the calculation function of the stability and reliability of the surrounding rock of the spray-anchor supported hydraulic tunnel.And based on the difference principle,the traditional reliability algorithm is inconvenient to solve the problem of implicit function function,and it provides a research foundation for the reliability calculation and analysis of spray-anchor supported hydraulic tunnels.(2)The reliability algorithms of the first second-order moment and the second-order second moment based on the difference principle are proposed.Taking the calibration algorithm(ie Monte Carlo method)commonly used in engineering as the reference standard,the accuracy and efficiency of the algorithm in this paper is verified through the analysis of the engineering example of spray anchor supporting hydraulic tunnel.Sensitivity analysis and discussion on the random variable cohesive force c and internal friction angle φ that affect the stability and reliability of the surrounding rock of the hydraulic tunnel supported by shotcreting and anchoring are carried out.The results show that the calculation results of the method proposed in this paper are accurate and efficient,and can meet the calculation requirements of actual engineering.The negative correlation of c and φ has a significant impact on the stability and reliability of the surrounding rock of the tunnel,and the sensitivity of the random variable φ is stronger than that of the random variable c.(3)Based on fuzzy theory,considering the fuzziness of random variables and failure criteria separately and comprehensively,the fuzzy reliability of the stability of the surrounding rock of hydraulic tunnel supported by shotcrete is studied.Among them,the ambiguity of random variables is dealt with by the α-level cut-set method,and the ambiguities of the failure criterion are respectively considered by the α-level cut-set method and the reduced-half trapezoidal membership function.At the same time,the influence of the negative correlation between the random variable cohesion c and the internal friction angle φ on the reliability calculation results is studied.The results show that the instability of surrounding rock reflected by the fuzzy reliability study of the surrounding rock stability of hydraulic tunnel supported by shotcrete is a transitional process which is more in line with engineering reality.The result is more accurate and reasonable when the interval of the reliability index βis processed by using the reduced-half-ladder membership function.With the increase of the negative correlation of c and φ,the fuzzy reliability index β keeps increasing.In this paper,quantitative reliability analysis of the surrounding rock stability of hydraulic tunnels supported by bolting and shotcreting is carried out,and theoretical analysis is combined with engineering application.Taking full account of the random and fuzzy uncertainties in the project,a new set of calculation and analysis methods for the stability and reliability of the surrounding rock of the tunnel are proposed.The research results provide theoretical reference and technical support for in-depth study of the stability and reliability of the surrounding rock of hydraulic tunnels.