Stability Analysis Of Slope By The Inverse Reliability Method

The stability analysis of slope is one of the most important questions in geotechnical engineering. Many methods of slope stability analysis can be summarized into two categories:deterministic methods and probabilistic methods. Deterministic methods, such as Limit equilibrium method which is traditional method in slope stability analysis uses factor of safety to evaluate stability of slopes, are the basic method of slope stability analysis. Because of factor of safety brief and easy to understand, it is widely used in engineering. But many sources of uncertainty are involved in the analysis; Factor of safety hardly reflects stability of slope truly. The reliability method as a method of probabilistic methods evaluates slope stability by reliability index or probability of failure. The reliability method considers the uncertainties of soil properties in slope stability analysis, so compared with limit equilibrium method is more reasonable, but its application is limited because of imperfect in theory. Address these issues, the inverse reliability method is proposed in slope stability analysis, calculate factor of safety at a given reliability index. Thus, the proposed method learns the advantages of both above method:briefness of Limit equilibrium method and reasonable of reliability method, to composite evaluate slope stability. This is also consistent with trends that the use of various methods to estimate slope stability.In this paper, it introduces the basic theories of stability analysis and reliability analysis,firstly. On the basis of these, take deeply study of the inverse reliability method, and take much time to introduce the inverse first order reliability method (FORM). Based on the above mentioned theory, schemes of inverse reliability analysis at Terzaghi Model and Bishop Model are established, which are in connection with circular slip surface. Some examples have been used to test and verify feasibility of the inverse reliability in slope stability analysis. Then, the method is extended to stability analysis of non-circular slip surface slope. Based on Janbu and Spencer Models, the format and calculation steps are establish for inverse reliability analysis.Based on the above analysis, a program using Visual Basic 6.0 language has been developed and it can run in Windows environment. The program can use the inverse reliability method and Limit equilibrium method to evaluate stability of slope with multilayer and arbitrary slip surface. It facilitates comparison of results.Then, several examples are discussed by the program of the inverse reliability analysis, and the results will be compared with the deterministic analysis, which show that slope stability analysis, ignoring the variability of geotechnical parameters, will lead to overestimation of the slope stability, so that slope is unsafe. The inverse reliability method developed to slope stability evaluation not only meet a given reliability level, but also take into account the uncertainty of geotechnical parameters, to better reflect the real situation of slope. At the same time, it is convenient to application and evaluates the slope stability by safety factor in engineering project.