Upper Bound Analysis Of Slope Stability And Approaches To Parameter Back Analysis

Slope stability problem is a commonly encountered issue in highway and railway engineering, how to make an accuracy slope safety evaluation is one of the most focused problems for geotechnical engineer. The commonest slope stability methods are limit equilibrium, finite element method and limit analysis. The limit analysis, which has strict theory basis and vigorous mathematical inference, is used to solve the ultimate load and critical height by conducting kinematically admissible velocity field or static permission stress field. Especially in some three dimensional slope stability analyses, it is not necessary to solve large-scale equation system as in limit equilibrium, which simplied the solution process. In this presented study, applying limit analysis upper bound theorem, a series of slope problems, such slope strength parameter back analysis, slope stability analysis in two and three-dimensional condition, were studied. The main content of research is as follows:(1) The relationship between the crirtical slip surface depth and soil strengtrh parameter was described. By combining the strength reduction method with upper bound theorem, the function of critical slip surface was obtained, as well the slip surface depth. Based on this depth, the strength parameter of homogenous soil, rock slope were back analyzed.(2) A new kinematically admissible velocity field of long slope was constructed, and the work rate and internal energy dissipation were solved. The stability factor formulation of this slope leads to a classical nonlinear programming problem, of which the constraint condition is given. The same failure mechanism was also applied to the local stability analysis of slurry trench, and the influence of slurry trench safety factor was discussed.(3) Slope stability was analyzed by three-dimensional failure mechanism. This failure mechanism is composed by rotational and transnational failure mechanism. The failure surface has the shape of a curvilinear cone, with upper and lower contours defined by log-spirals; all radial cross-sections of the surface are circular and the diameter of the circular increases with the angle of log-spirals. In the special case of cohesive soils, the shape of the failure surface reduces to toe. Applying this failure mechanism, the series three-dimensional slope stability issues was discussed, such the long slope considering the volumetric strain or not, the common two-step slope with the slip surface crossing the point in front of slope toe. The effect of parameters, like strength parameter, slope angle and earthquake force, on the stability was studied.(4) The three-dimensional stability for cohesion soil slope and slurry trench was researched, and the3-D stability problem for common slope was studied as well. The failure mechanism for cohesion soil was a spherical mechanism with the centre of sphereis located above the slope surface, the intersection of the sphere and the slope was considered as the sliding mass. For the analysis of3-D stability for normal long slope, a three-dimensional failure mechanism was proposed. This mechanism was determined by several key points and the function of the intersection of the sliding mass and the slope surface. The formulation for external force work rate and internal energy disputation was presented. A simple algorithm was proposed. By the simple method, the critical height for normal slope was obtained when the intersection function is parabola.(5) By slope slip surface generating applying discrete method, the upper bound analysis for inhomogeneous slope was researched. Through the discrete method, the coordinate of certain points in slip surface and the tangential direction of this can be computed. When the number of these points is larger enough, the approximate, composed by the straight line between these key points, is quiet similar with the analytical surface. The external and internal work rate of the approximate was computed, and then the ultimate load on slope top and the slope critical height can be obtained.(6) According to a slope engineering located in Zhejiang province, based on the analysis of sliding model, the strength parameter was back analyzed by slope inclination data. Furthermore, the2-D and3-D safety factor was obtained by upper bound theorem. There are115figures,16...