The Point Safety Factors Of Slope Strength Subtraction Criterion And Research And Engineering Application

There are some disadvantages in the limit equilibrium methods applied for solving the slope safety factors, so the present paper solved a slope safety factors based on three different critical failure criterions of the strength reduction method, which were the connectivity of plastic zone criterion, the displacement mutations criterion and the numerical computations convergence criterion, then by the comparisons of the results, the applicability of them were discussed, what is more, to the limitations that both the limit equilibrium method and the strength reduction method only got the total safety factor, and they were both in lack of consideration of the slope specific parts’stability in tension, the programs of solving the point safety factors was written in the FISH languages of the finite-difference numerical software FLAC3D, and after the post-processing the results were all output; at the last, the methods and principles above were applied in engineering examples, the deformations (displacements), stress situations of the final slops were analysed for the mechanical response characters of the slopes after the final excavations, safety factors of the final slops were gotten, under the weakening of the final slopes condition, the deformations and failure mechanisms of the final slops were analysed. The main contents and conclusions are:(1) A hyperbola regression equation was set up in this paper, which showed the relation between the displacements and reduction coefficients, and the slope safety factor can be obtained, but it was bigger in this way.(2) Under the weakening of the final slopes condition, the plastic zone of slopes would develop and expand gradually and then became connective finally, and the range of the plastic zone was consistent with slip mass searched by limit equilibrium method, it was very straight forward to get the safety factors of the slops in this way, but it based on the human’s judgments and tended to be conservative to some extent.(3) It was simple and convenient to get the slope safety factor by computer program based on the numerical computations convergence criterion, but there were other uncertain factors in this criterion.(4) Based on mathematical catastrophe theory, the paper established cusp catastrophe model of the slope horizontal displacement. And then the mutation characteristic values were calculated, it showed that as the value was less than zero,it meant the displacement had mutated and then the slope safety factor can be gotten reasonably.(5) It is suggested that different critical failure criterions should be combined, and get the average value of different failure criterions and methods in slope stability analysis.(6) The program of solving the point safety factors was written in this paper in the FISH languages of the software FLAC3D, the result showed both the distributions of point safety factor (between0and1) and the plastic zone of slopes are relatively closed in every step of the slope strength reduction.(7) It shows that by theory and engineering examples the comprehensive analytical method of strength reduction and point safety factor is a better effective method applied in slope stability.