| Stability control against sliding is a basic control in design of gravity dam. With the rapid increase of dam height, modern gravity dam design theory holds that, not only dam stability against sliding along the base surface but also stability against sliding in deep layer should be controlled and the latter is more important.There are 3 typical methods in using rigid limit balance theory to analyze the dam stability against in deep layer, they are Passive Stress Method, Remained Pushing-force Method and Equal-k Value Method. Fact of these methods existing concurrently and importance of control stability against sliding shows that the dam stability against sliding in deep layer is a significant problem in modern gravity dam design which should be well settled but not be settled well yet.The study of the thesis shows that, all the above 3 methods are wrong.There are 2 key problems when using rigid limit balance theory to analyze stability against sliding in deep layer, what factors can be used to solute inner force R of inner crack surface? And how to solute K value through the safety coefficients of stability against sliding, k, k2 of two the sliding block.The mathematical expression of inner force R is not single because of relation with the following 2 conditions whether the tangential stress overcomes their own maximum tangential stress, and the kinetic state of the system. Therefore, sliding block is divided in 4 kinds, system is divided in 6 groups in the thesis, and calculating formula of each group is obtained. The current 3 methods all have hypothesis, the first two method separately assume sliding block 2 and sliding block 1 reach critical balance state first, while Equal-k Method assume the safety coefficients of the two sliding block is equal. The study of the thesis shows the R has theoretical solution, not need assumption at all.Dynamic coefficient Kd is defined in the thesis to transform the problem of K1, K2 to solving Kd , a reciprocal of K is an index to show unit mass sliding block pushing motion.K1d and K2d have a weighted average relation . Thus theoretical formula of solving K through K1 and K2 was obtained according to weighted average relation of Kd , and Kd must be a medium value of K1d and K2d. K must be a medium value of K1 and K2 can also be gotten, which shows that solving K through K1 and K2 is feasible in theory. Meanwhile it shows that the first two methods are obviously wrong by separately define K as K1 and K as K2. And latter method which defining K values must be equal is too stiff, which only be right on some special conditions, while it is wrong in universal conditions.Through the research in friction-sliding model of two sliding block through horizontal sliding surface, the dynamic coefficient method for analyzing stability against sliding of two sliding blocks is put forward, and the method is further expressed as dynamic coefficient method for analyzing stability against sliding of gravity dams. Dynamic coefficient method subordinates to rigid limit balance method, its basic contents includes:Two sliding blocks is divided in two groups and four sub-groups according to their stress state and location.System is divided in 6 types through combination of sliding groups and sub-grouping of kinetic state.Different types inner stress of inner crack surface is calculated using corresponding formula.Anti-forces N1, N2, T1, T2 are solved using force balance equations. Maximum anti-sliding force of the sliding surface are solving separately.Safety coefficient K1 and K2 of sliding blocks are solved separately.Safety coefficient of the system K is calculated.Through the transition of block diagram, the analysis software for gravity dam stability against sliding in deep layer is developed. Using the software to draw relation curve of K and other parameters, comparison of the result with which current 3 typical methods further shows that the 3 typical methods ate wrong, while the dynamic coefficient is superior for proper stressing and K value calc...
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