Study On Determination And Application Of Slope Safety Factor Under Seismic Action

Mountainous is the outmost character of China, which objectively determines that amounts of natural slope have been existed. At the same time, we have also been in the infrastructure construction of rapid development period, thus massive artificially high slope are inevitably formed. Meanwhile, China is located between the world's two biggest earthquake intensively occurred zone of the Pacific seismic belt and the Himalayas-Mediterranean seismic belt. With the extrusion of the Pacific plate, the Indian plate as well as the Philippines sea plate, the seismic fault zones are well developed. So the dynamic stability analytical study for the slope has great practical significance. Therefore, some preliminary research works for the slope safety factor under seismic action are taken in the paper.This paper mainly includes the following aspects:①The research significance and contents are pointed out, and the research status of the slope stability under seismic action are reviewed that include the slope stability analysis method under seismic action as well as the dynamic properties of the rock-mass and soil-body and the mechanism of instability. Meanwhile the existing stability analysis problems for the slope under seismic action are presented.②The constitutive model, failure criterion, flow rule and the great-small deformation hypothesis, which were frequently used in the stability analysis of slope were expounded. And the definition and principle of strength reduction finite element method, as well as the failure criterion were explained.③The pseudo-static limit equilibrium, pseudo-static strength reduction finite element method and the pseudo-static finite difference method were discussed. With an example, the safety factors calculated by the above methods were compared.④Combining the safety factor time history, several methods for determining the dynamic stability safety factor were analyzed and compared with the conventional pseudo-static methods.⑤With the application of the finite-difference analysis software (FLAC3D), the dynamic strength reduction was used to calculate an example. And the slope dynamic stability state was judged by the trends of the end time-history of velocity and displacement for the critical points of the potential sliding body.⑥Combining with an engineering example, the dynamic stability factor of the slope was calculated through the pseudo-static method, dynamical finite element slope safety factor time history methods and complete dynamic analysis method. According to the calculation results several reasonable methods for evaluation the slope dynamic stability methods were presented.Based on the research and analysis of several slope dynamic stability safety factor solving methods that was proposed in the paper, the following conclusions were reached: 1) Pseudo-static method has virtues with simple calculation and convenient application for engineering in solving the slope dynamic stability safety factor. But the method was obtained adopted by using static method under the static load and it cannot incarnate the dynamic characteristics for the slope, so it is just a empirical algorithm. 2) The dynamic finite element time history analysis method converts dynamic problems to static and adopts static limit equilibrium method to solve the dynamic stability safety factor of slope. To a certain extent, it considers the slope dynamic response, but it cannot get position of the shear fracture plane. So the position of the dynamic shear fracture plane can only be obtained by experience or static the methods. 3) Complete dynamic analysis method can perfectly considers the dynamic response. So it is more reasonable and reliable in evaluating the slope dynamic stability.Through a project example, the safety factors calculated by various methods were compared in this paper and the minimun average safety factor, the reliability dynamic safety factor as well as the complete dynamic analysis methods were recommended to calculate the safety factor for evaluating the slope dynamic stability. The achievements have realistic meanings for the evaluation of slope dynamic stability in high-intensity earthquake area.