| Alpine gorge geomorphologic landscape is widely developed in the slopedescending zone arounding the eastern Qinghai-Tibetan plateau.Slopes in this region possess the characteristics of great gradient and high initial ground stress.With the rapid crustal uplift,erosion of river valleys get faster,causing intense unloading environment around this area.Geological disasters hanppen frequently in this region,among which toppling deformation is often found in steep layered rock slopes,resulting in serious consequences such as loss of life and property.Influence factors of toppling deformation is so complicated that it can't be accurately known whether further deformation will take place or not after time-dependent deformation.At present,knowledge about toppling instability mode is far from enough to differentiate all kinds of toppling slopes after so many kinds of topplings are found in recent years.Thus,Goodman & Bray's classification is still used today,but it seems that it is not perfectly suitable while masses of topplings appear.Stability of toppling slope is one of the most important and concerned issue during engineering construction,unfortunately,there's not any simple and precise method to figure it out.On these issues,the influence factors are summarized and the controlling factors are gained by regression on the basis of collecting materials of 33 examples of toppling slope.Five instability mode are come up with based on the slope geological structure,deformation characteristics and mechanism.Finally,SVM is applied to build the prediction model of stability of toppling slopes.Aimed at toppling slopes,engineering geology,rock mass mechanics,statistics and numerical simulation are applied to conduct the following research:(1)33 examples(23 examples of anti-dip slope and 10 examples of bedding slope)of large-scale toppling slope are collected,the spatial distribution and compose features are analyzed,and then the geological environment characteristics are summarized.(2)The influence factors(including internal and external factors)of toppling deformation are analyzed,and then the Uniform Design is applied to design the slope models with several factors and different levels.UDEC is also utilized to simulate the deformation of these slopes.(3)MLR is applied to analyze the relationship between toppling deformation and influence factors,and the controlling factors are gained.(4)Classification of toppling slopes is performed according to dip direction,cause,deformation section and course of evolution of toppling(single factor).Also,the classification is performed according to lithology,deformation features,rock mass structure and slope structure(multiple factors).(5)The lithology feature,slope geological structure,characteristics of deformation of typical toppling slopes are summarized,on this basis,five instability modes are put forward,which are bend-tension-shear,topple-snap-shear,unload-bend-topple,compress-bend-topple and compress-tension-topple.PFC is applied to analyze the failure mechanism of each mode.(6)The evolution of toppling deformation and failure is analyzed,on this basis,the influence of stability of toppling slopes is studied.A lot of example of toppling slopes are collected,whose influence factors of stability and actual safety factors are extracted to act as index to support the SVM prediction model.Finally,taking Erguxi toppling slope for example,its' stability is predicted by using SVM model,which is compared to that evaluated by regular methods,it turns out that the result gained by SVM is accord with regular methods,and SVM model is accurate and practical. |
PDF Full Text Request