Vector Sum Analysis Method Of Slope And Dam Foundation Stability Against Sliding

Stability analysis of slope and dam foundation against sliding is a classic research field in rock and soil mechanics. Although there are a lot of research results in this field, the analytical basis of commonly used methods, defining their safety factors with the ratio of the algebraic sum of forces against sliding to that of forces driving sliding, lacks physical meaning under most engineering conditions. the stability analysis method meeting engineering needs is the method that is of clear physical significance and solid theoretical foundation, as well as simple and practicable. This thesis attempts to do some studies and discussions on this issue. The main studies and conclusions of this thesis are as follows.(1) State the significance of stability analyses of slope and dam foundation against sliding. The stability analysis methods, available in the literature, are reviewed. Aiming at the problems of common analytical methods of stability analyses, the main studies in this thesis are presented.(2) Discuss the definitions of two kinds of safety factors, the overload safety factor and the strength reduction safety factor, in common analytical methods of stability analyses. The force integral of the two safety factor definitions along the slip surface is ambiguous in mechanics. It is different from the real strength properties of rock and soil masses reducing the two strength parameters with a same coefficient as applying the strength reduction method. The overload safety factors calculated by overloading at different directions are out of comparability. The stress state with which the safety factors of the two definitions are calculated is obtained in terms of arbitrary assumptions. Thus the significance of the two safety factor definitions is questionable.(3) Put forward the vector sum analysis method of slope and dam foundation stability against sliding (VAM), and define the vector sum method safety factor (VF), based on the vector characteristic of the sliding motion. After the stress distribution calculated with the finite element analysis, on the basis of the friction theory and the slip surface stress, the direction of the sliding tendency of slope and dam foundation as a whole can be determined. Taking the direction as the calculating direction, the VF is defined as the ratio of the algebraic sum of the projections of anti-sliding forces to that of sliding forces along the slip surface at the calculating direction. The significance of the VF is clear in physics. The calculating process of the VF is simple and that facilitates the application of this analysis method in engineering. (4) Theoretical analysis shows: under the special condition of the circular or single line slip surface, the formula of VF and that of the safety factor defined with the ratio of the algebraic sum of anti-sliding forces to that of sliding forces in rigid body limit equilibrium methods are equivalent, as taking the slope as the rigid body sliding.(5) Apply the VAM to analyzing the stability of several simple slope cases. The results indicate: the calculated values of the safety factors applying VAM are close to that applying the limit equilibrium method under the circular slip surface or the single line surface condition, but there is some difference between them under other slip surface conditions, and the value of each case's VF is less than that of the strength reduction method of FEM.(6) Apply the VAM to calculating the VF of the deep sliding stability of 3# dam foundation of the left power house of the Three Gorges Project. The results show: the more steep and deep the potential slip surface is, the less the VF value is; the VF value of the potential slip surface that contains joints ABCFH is less than that of others, and it is coincident with the qualitative analysis results with finite element strength reduction method available in literature. The application of the VAM to the practical engineering verifies its feasibility and practicability.(7) Propose the vector sum analysis method of the slope stability taking the dynamic loads induced by blasting seism into account (BVAM), based on analyzing the dynamic effect differences between the natural seism and the blasting seism. The BVAM calculates the VF with VAM, combining the time history method and the pseudo-static method, and analyzing the state stress inside the slope at any point and at any time by FEM with the coaction of inertia forces due to blasting vibration and static loads on the slope. The BVAM well reflects the time history characteristic of the slope under blasting vibration.(8) Solve the VF of the bottom final wall slope of Huangmailing Phosphrite Mine with the BVAM on different work conditions. The results show: in terms of an individual blasting, the VF influenced by the blasting vibration decreases within 10 percent compared with that of the static loads; that the minimum of the VF under the blasting conditions of the Mine is 1.119 is coincident with the real state of the slope that the slope is generally stable now; but that the safety factor value calculated with the pseudo-static limit equilibrium method is merely 0.669 is too far away from the real state of the slope.