Study On Reliability Analysis Of Slope

Safety factor method and reliability index method are two typical stability analysis methods for slope. Some problems in the reliability analysis of slope are studied here. It's includes:(1) A more accurate calculation formula of the safety factor for homogeneous soil slope with and without the resisting part of circle surface failure is established using analytical method. Based on the shear strength parameters, the relationship and difference between the safety factor method and the reliability index method for slope stability analysis are investigated. A program is developed accordingly; some regularity and the influence of statistical characteristics of soil strength parameters on stability analysis for pure clay slope and impure clay slope are studied.(2)A model of the slope fuzzy-random reliability analysis is found basis of the fuzzy interval of the limit state variable near its zero value. The influences of width fraction and migration fraction is studied in different situations include the variability of common soil parameters and the distribution of membership function of fuzzy probability of failure. The results obtained by the fuzzy and deterministic method are studied based on contrastive analysis.(3) The safety factor (F~i) and failure probability (P_f~i) of each slip surface is calculated for the soil slope with circle surface failure. The variable character of strength parameters is considered. The reliable probability (?) are used to estimate the creditability of F~i by calculating the reduced safety factor (?); A slope stability evaluation system is founded using the minimum reduced safety factor F_R=min(F_R~i).(4) Response surface method (RSM) is an accepted and efficient technique in the reliability analysis of large and complex structures with implicit limit state function. It is noted that the accuracy of RSM is depended on the choice of sample points but the effect of varying their location has had little attention. In the present study, two sample point selection strategies, the direction cosines projected strategy (DCS) and the limit step length iteration strategy (LSS), are investigated to improve the fit of the RSM. Since it needs no iteration to fit the response surface function (only one response surface is fitted), and since it is more suitable for highly non-linear problems, the proposed improved RSM should be practical in actual reliability problems. (5) The normal transformation polynomial is used by some researcher in practical probabilistic analysis in structural or civil engineering; especially when multivariate random variables with the probabilistic characteristics expressed using only statistical moments are involved. In this study, a moment method improved by the third-order normal transformation polynomial for practical slope reliability analysis with random variables having unknown distributions is discussed. Of particular importance in this work is the conclusion that although the application of the improved moment method to several examples is approving, its flaw should be recognized. First, the moment method cannot predict accurate results for some problems with small failure probability. Second, it may provide totally different estimate of reliability index for different equivalent formulations of the same performance function.(6) An approximate second-order second-moment method (SORM) for structures with dependent random variables is investigated. A closed calculation form of the curvature is given based on the theory of matrix.(7)A case study of high slope reinforcement is presented. The whole process of the uplift test and the computer simulation of cable are expatiated. The excavation of the slope with or without reinforcement is simulated by numerical method. Together with the conclusions of reliability analysis, the reinforcement is proved to be effective for stabilizing the slope.