| In the four geological disasters, the hazard of land sliding goes after that of earthquake and volcano, but comes before debris flow. However, considering the frequency and distribution area of land sliding, the hazard to human being caused by land sliding is more serious than any other geological disasters. Since 1950s, we have had a great progress in studying land sliding, and obtained abundant practical experience in prevention of land sliding, thus the loss declined a lot. However, due to the needs of the development of economy, a great deal of human projects were constructed from land to sea, from plane to mountain areas which cause the change of the nature environment and make new land sliding disaster more than nature land sliding.Hongyanhe Nuclear power station locates in hilly country which is high in north and low in south. From South to Forth, the land has three terraces with the elevation of 3m, 8m, and 20m. In the process of digging of foundation ditch, a 30m artificial slope is generated which influent the construction of the project and the safety of the workers'lives. Because of the reasons above, it plays a typical important role to do the research of reliability analysis of stability of artificial slope in the foundation ditch of pump room of Hongyanhe Nuclear Power station.Currently, the analysis method of evaluation of slope stability can divides into qualitative analysis ways and quantitative analysis ways. Qualitative analysis ways include Geological Analysis method, Geological Engineering Analogue method, graphical method, and Slope stability expert system, etc. in practice, Quantitative analysis ways are more widely used which can also be divided into certainty analysis methods and uncertainty analysis methods. In certainty analysis methods, the factors such as the parameters of rock or soil mass, structure model of slope, which can influence the slope stability, are considered as certain parameters. Based on these certain parameters, the evaluation of slope stability are performed in some certain ways: Slice method including Fellenius method, Bishop method, Janbu method, Morgenstern-Price method, residual thrust method, and Sarma method, etc; Numerical method including Finite Element method, Boundary Element method, and Distinct Element method, etc. In uncertainty methods, the factors influence the slope stability are regarded as the probability function in a certain probability distribution which is more closed to the the practical condition. The uncertainty methods include Grey theory method, BP neural network method, fuzzy comprehensive evaluation method, etc.Reliability analysis of slope stability is one of the uncertainty analysis methods, which include Monte-Carlo Method, Reliability index method, statistical moment method, and Stochastic Finite Element method, etc. Response surface method is a new reliability analysis way introduced into Geotechnical engineering in recent 10 years, before which, the method has been widely used in biology, chemistry industry, machinery, and so on. Combining the response surface method with other methods listed above can make the process of solution simple with a clear thinking and high precision to satisfy the needs of geotechnical engineering.The soils of the artificial slope of foundation pitch in pump room are weathered sand, strongly weathered granite, medium weather granite from the top to the bottom. The boundaries of the strata were obtained by drilling and the grade of the slope is 1:1.5. Due to the lack of the initial data, there may be some error when determine the distribution of the physical-mechanical parameters and characteristic parameters. Because of this, a lot of literatures are read to choose plenty of mechanical parameters of strongly weathered granite who has the similar Young's modulus, Poisson ratio and weather condition. Probability distribution and characteristic parameters of every mechanical parameter are obtained by mathematically statistic method, which can provide a solid foundation to reliability analysis of slope stability.In this paper, response surface method is combined with Morgenstern-Price method to become the improved response surface method. The idea is that: substitute M-P method for Finite Element Method in response surface method and introduce the concept of factor of safety to response surface method. Complex process of solution of stress and strain in finite element method is replaced by the calculation of factor of safety. When the factor of safety is less than 1.0, the slope can be considered as destroyed. In this paper, the Slope module in the software Geostudio and M-P method are used in calculating of the factor of safety. The iterative process in reliability index method is applied in calculation of reliability index with the state function of quadratic fitting response surface function. Because fitting of response surface function, iterative calculation of reliability index, and multi fitting and iteration of response surface function are involved in the whole calculation, Matlab programming is used and satisfied results are obtained.In this paper, sensibility analysis of mechanical parameters to the reliability analysis of slope stability is also studied. Unit weight, cohesion, and internal friction angle are considered as the variable of the reliability analysis. A series of reliability index are obtained when coefficients of variation of two of the variables are fixed and the last one changes in a certain law. And then the coefficient of variation-reliability index chart is generated to get the sensibility of every parameter to the reliability of the slope stability.Conventional slope stability analysis ways do not consider the random of the parameters which, however, is considered in reliability analysis. The improved response surface method applied in this paper has a clear thinking and the results have a little error compared with the results of Monte-Carlo method. At last, some advices about research direction and advantages are given.
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