Study On Evaluating Safety Degree Of Roadbed Slope At Slippery Stratum In Chongqing Three Gorges Area

The investigation indicated that more than 50% of large-scale roadbed disasters in Chongqing Three Gorges area occured in the Triassic badong group,The Jurassic zhenzhuchong group and the quaternary Colluvial product formation. And this kind of strata is called as easy slippery stratum.The use of Safety coefficient Evaluation ignores the uncertainty factors in the process of stability analysis of Roadbed side slope in Easy slippery stratum, leading to the influence on the accuracy of evaluation on side Slope safety. In order to make a complete and correct evaluation on Roadbed side slope in Easy slippery stratum, this paper adopted the innovative appraisal method of safety degree and realized the enrichment and supplement to the traditional safety coefficient and eventually got the more comprehensive and substantive evaluation of the roadbed side slop in easy slippery stratum.The appraisal research on Safety degree of roadbed slop at slippery stratum in chongqing three gorges is mainly embodied in the following aspects:①Through the field research on the roadbed side slop in easy slippery stratum and the full collection and analysis of previous research material and achievement, we get the Geological characteristic of the Triassic badong group and The Jurassic zhenzhuchong group and then obtain the important reasons for Slope failure and the influence effect of rainfall, reservoir water level fluctuation and water storage on roadbed slop.②Through analyzing the defects of stability analyses methods of the present roadbed side slope, from the definition of traditional safety coefficient, combined with the method for solving the reliability index, we Put forward the innovative concept of safety degree and deduce the formula for the index of safety degree. Then we get the corresponding relationship between the traditional safety coefficient and the index of safety degree on this basis.③Through direct shear tests, we get 100 rock Physical parameter datas and analysis of the data, and we get the conclusion that Physical and mechanical parameters of rock Conform to normal distribution.④Through the search of literature and the conduct of numerical simulation, we get the inherent weakness of normal distribution in the numerical simulation. We put forward the improvement method of the normal distribution random number in order to overcome this weakness.⑤Through the analysis of existing data, we completed the deduction of integral expression of safty factor of slope and write a Matalb program Combined with the monte carlo method to solve a slope reliability, the index of safty degree.⑥Through the safety evaluation on traditional safety coefficient method, Reliability analysis method and Safety degree analysis method to the roadbed side slope model, the result shows that Safety degree analysis method fully gets the advantages of traditional safety coefficient method and Reliability analysis method and Safety degree analysis method corrected the static and absolute disadvantages of safety coefficient method appraisal on side slope and overcame the boring solution process of Reliability analysis method.⑦Through the Combinition with practical engineering, we promote the Safety degree appraisal method into the Line sliding surface slope and realize the use of Monte Carlo method in the transfer coefficient method.⑧By changing the slope ration and the height of slop, we get different failure probability, and through the linear fitting to the data, we get the relationship between failure probability and slope ration,the height of slop.