Evaluation And Application Of Highway Slope Stability Based On Random Fuzzy Reliability Theory

With the continuous improvement of the expressway network,in recent years,the expressway gradually develops to mountainous areas.The mountainous area has complex geological conditions,diverse topography and other characteristics.In the early stage of highway construction,considering the safety,cost,construction period and other issues in the construction,the route selection planning is carried out.Through human activities,the original landform is changed,the original balance state is broken,and the slope stability is affected to a certain extent.The limit equilibrium method is usually used to evaluate the slope stability,and the relevant parameters are regarded as fixed values for calculation,and the stability of the slope is judged by the size of the safety factor.However,due to the heterogeneity of rock and soil,the difference of occurrence environment and region,there are randomness and fuzziness in the parameters and calculation model of slope stability analysis,which lead to large deviation in the judgment of slope state.Therefore,it is of great practical significance for highway construction in mountainous areas to seek an effective evaluation method of slope stability considering the uncertainty of geotechnical characteristics.Based on the background of Longchuan HUAIJI A1 section of Shantou Kunming expressway,aiming at the uncertainty of slope engineering,this paper adopts the fuzzy reliability theory and establishes the fuzzy reliability calculation model to evaluate the stability of the slope along the expressway.The main research work and achievements are as follows:(1)This paper introduces the general situation of the project of Longchuan HUAIJI A1 section of Shantou Kunming expressway.The study area is a complex landform with all kinds of topography.48 cutting slopes,31 embankment slopes and 8 half excavation and half filling slopes are mainly deep cut slopes,of which the lithology is mainly strongly weathered granite,followed by argillaceous sandstone and sandy gravel,most of which are more than 15 m high and the slope angle is 15 ° Up.(2)Study on failure mode and influencing factors of slope stability.According to different engineering properties,the slope along the line is divided into embankment,cutting and shoulder slope.The results show that the failure mode of embankment slope and cutting slope can be regarded as circular failure,and the shoulder slope can be regarded as broken line failure.Based on the engineering background,the influence factors of slope stability are analyzed by using frequency statistics and grey correlation method.The results show that the formation lithology,topography,geological structure,hydrology and rainfall are the main factors affecting the slope stability,and the gray correlation degree of slope parameters is: cohesion > internal friction angle > slope angle > gravity >slope height.(3)Fuzzy reliability theory and its application in slope stability evaluation.Bishop method and simplified Morgenstern price method are selected for circular arc failure and broken line failure respectively.The formulas of sliding force and anti sliding force of slope under natural state are derived,and the limit state equation is established,and programmed by MATLAB program.On this basis,the failure of slope is regarded as a fuzzy event,and the parameters of geotechnical mechanics are treated with fuzziness.The failure process of slope is described by the membership function of ridge type,and the fuzzy reliability calculation model combining probability density function and membership function of limit state is established.The model algorithm is implemented by MATLAB program language,and its correctness is verified by a case study in literature.(4)Background engineering application and highway safety evaluation.With the help of the existing conclusions,the typical slopes are screened,and the limit state equations of each typical slope are derived to evaluate the stability.The slope stability is divided into five grades: stability,basic stability,potential instability,under stability and instability.The results of random fuzzy reliability are used to evaluate the slope stability.The results show that of the 87 slopes along the study area,67 are stable,3 are basically stable,1 is potentially unstable,1 is under stable,and 15 are unstable.Through the analysis of the safety factor and failure probability of the slope along the line,it is proved again that the selected membership function is in line with the reality.