Evaluation Of The Carbonaceous Shale Slope Stability Based On Grey Theory

Carbonaceous shale is a kind of expansive soft rock with low strength,easy weathering and disintegration.Carbonaceous shale slope is prone to collapse and landslide failure because of weathering disintegration,which it caused greater security risks.Therefore,it is very important to value to evaluate the stability of Carbonaceous shale slope.The stability of the carbonaceous shale slope is composed of many factors,and there is a complex uncertainty,which can be regarded as a grey system.In this paper,the high slope in the highway rebuild and extension engineering of Guangxi Liuzhou to Nanning highway of the carbonaceous shale slope was took as an example,which used gray correlation analysis and gray prediction model to study the stability of Carbonaceous shale slope stability evaluation.The main research results are as follows:(1)Under the two different conditions of the indoor disintegration test,it is concluded that there is a certain correlation between the disintegration rate and the dry and wet condition.In the disintegration process and after the disintegration of the rock mass observation found that the collapse mechanism mainly includes two stages: One is the continuous expansion of rock mass fracture;the two is the rock mass crack all through.The main factors affecting disintegration were obtained by gray correlation method,and illite mass fraction was the most sensitive factor,which showed that illite was the most unstable clay mineral component.(2)Based on the orthogonal experiment design,the influence factors of slope stability are analyzed by the grey correlation method.The results show that: A number of factors that affect the sensitivity of the order: internal friction angle > severe > cohesion > slope height >slope angle > rock slope,and the sensitivity of the single influencing factors is sorted to:internal friction angle > severe > cohesion > rock slope > slope height > slope angle.The sensitivity results are in the order of sensitivity in the region under specific conditions.(3)The carbonaceous shale slope grading excavation process stability numerical simulation analysis is carried out.The results show that: when the excavation Step3 after the completion of the slope is the most unstable state,After the excavation of Step3,the real-time reinforcement scheme is put forward,and the stability of the slope after the excavation ofStep3 is satisfied with the standard.(4)Comparison of cumulative displacement settlement and theoretical calculation of the site monitoring points of the modified and expanded carbonaceous shale slope under the condition of non support and support,that both have the same variation law.The traditional grey GM(1,1)model is used to predict the displacement of the unstable slope after excavation of Step3.The results show that: the surface displacement of the slope is predicted to increase gradually,and the trend of the sliding is gradually increasing,and the slope will be in a steady state over time.But,using the traditional gray GM(1,1)model fitting precision is not high.Because of the traditional grey GM(1,1)model is not accurate,this paper proposes an improved polynomial fitting model based on least square method.Compared with the traditional model,the average relative error of the fitting sequence is reduced by 2.2% and29.7% respectively,and the mean variance ratio decreases by 0.116 and 0.064 respectively,The improved grey model has higher forecasting accuracy,it can reduce the risk of prediction,and the feasibility and reliability of the improved model is better.