Research On Evaluation Of Supported High And Steep Loess Slope Based On D-S Evidential Reasoning

This topic is based on the high and steep loess slope supported by HuangYan expressway,taking the evidence theory as the theoretical basis,combined with model test on anti-slide piles,experiment of the artificial rainfall of loess slope and laboratory test,an evaluation method considering the safety of retaining structures and the stability of high and steep slope is established,as well as the anti-slide pile cumulative horizontal displacement mainly,high and steep slope horizontal displacement as a supplement to the early warning index of the early warning value.In view of the safety of the high and steep slope of the supported loess,the characteristics of the interaction between the side slope and the supported structure,the factors affecting the stability of high and steep are analyzed comprehensively,nineteen basic index were selected,including shear strength,soil weight,silt content,compression modulus,poisson's ratio,daily rainfall,pore water pressure,runoff condition,slope height and slope,slope morphology,roof crack,cunulative displacement of slope soil,internal force and displacement of anti-slide pile.On this basis,the framework system of safety evaluation index for high and steep slope of supported loess is eatablished.On the basis of the sensitivity analysis of the some basis in the framework system of evaluation index by the grey relational method,the weight of each evaluation index is allocated by AHP.Based on the relation curves of load and displacement,load and internal force which obtained on the scale model test of field anti-slide pile,according to the slope,the change process of soil displacement,displacement of anti-slide pile and internal force of anti-slide pile were divided into safety state,basic safety state,critical state and failure state;Based on the relationship curve between rainfall and soil horizontal displacement,rainfall and pore water pressure obtained from artificial rainfall test on the loess slope,the ranges of daily rainfall,pore water pressure were also divided into four security states;Based on the curves of shear stress and displacement obtained from repeated direct shear tests in laboratory,According to the slope and the boundary point between critical state and failure state with peak point or strain hardening point,the change process of shear stress and displacement can also be dicided into four stages.Based on nineteen basic indicators and the safety state of slope is taken as identification frame,the interval number method is used to construct the basic probability distribution,an evidential reasoning method for safety evaluation of high and steep loess slope with support type is established,based on this method,the relationship between the accumulated horizontal displacement of anti-slide pile and the stress state of anti-slide pile as well as the relationship between the horizontal displacement of high and steep slope and the internal parameters of each index is established.the purpose of deducing the internal parameters of the slope based on displacement monitored on site is achieved,the analysis and determination of the internal parameters of the anti-slide pile and the slope soil are studied on the basis of the dynamic displacement monitoring.At the same time,the variation rules of internal parameters of anti-slide piles and high-steep slopes are obtained by iterating the historical data of horizontal displacement of anti-slide piles and high-steep slope monitored.According to the proposed evaluation method,the safety of the high steep slope of HuangYan expressway is evaluated,and the result show the evaluation results are consistent with the actual state of theslope,which verifies thefeasibility and accuracy of the method for the safety evaluation of the highand steep slope of the supported type loess.The safety evaluation method of high and steep slope of supported type loess based on evidential reasoning proposed provides a new approach for the safety evaluative of similar slope.