| Sub-horizontal translational landslides,which are one special kind of rockslides,are widely spread in Sichuan Basin in China.This type of landslide develops in sub-horizontal bedrock composed of sandstone and mudstone,with the dip angle is normally 3~5 degrees mostly.Because of its peculiar genetic mechanism,deformation pattern,invisibility and burstiness,this kind of landslide have got much attention from the researchers.At present,there is some dispute about the cause of the water-storage fractures of the landslide.The water-storage fractures are formed by the water-flowing structural plane,which not only controls the evolution of this kind of landslide,but also affects the movement characteristics of the landslide.In this paper,the main entry point is the internal and external geological forces coupling of Sichuan basin.First of all,by the study of a large number of data obtained the main tectonic deformation and tectonic stress evolution history of the various tectonic zones of Sichuan basin and the types and rules of the external dynamic action of Sichuan basin.The study reveals the coupling mechanism of internal and external forces during the evolution of landslide.The dominant factors and genetic types of landslide development in sub-horizontal strata in Sichuan basin were studied.The distance calculation model of landslide movement is obtained.The main factors influencing the distance of such kind of landslides are found.The following results are mainly obtained through this study:(1)According to the tectonic characteristics of Sichuan basin,the Sichuan basin is divided into six tectonic zones,and the tectonic characteristics and the evolution of tectonic stress fields are obtained through the study and summary.The main stress direction during the period neotectonics in different regions of Sichuan basin was obtained by using the improved A.E Scheidegger method.A large number of data are collected,including seismic source mechanism solutions,fault slip,borehole caving,hydraulic fracturing and stress relief.The nowaday characteristics of the tectonic stress field of Sichuan basin are obtained.(2)The study obtained the rule,type and intensity of external dynamic effect in different areas of Sichuan basin.(3)The mechanism of internal and external dynamic coupling in the evolution of sub-horizontal translational landslide formation is studied,mainly including:(1)Study on the structural characteristics of sub-horizontal strata slope with internal and external dynamic coupling.(2)On the basis of structural characteristics study results,the conceptual models of groundwater seepage are obtained.(3)Based on the research on groundwater softening and argillization effect,tthree types evolution mode of sliding belt is obtained based on the differentiation of the mechanism of internal and external dynamic coupling and the material composition of sliding belt of landslide cases.(4)The study has obtained the necessary spaial combination conditions for the formation of sub-horizontal translational landslides under internal and external dynamic coupling.(5)By summarizing the evolution process of this kind of landslide,the necessary conditions for the formation of the landslide are obtained,which are material conditions,structural conditions,spatial conditions,lunching conditions,triggering conditions.(4)Based on the tectonic stress field in the Sichuan basin evolution characteristics,dynamic characteristics and the internal and external power coupling action research,the Sichuan basin is divided into seven comprehensive regions.Research reveals the sub-horizontal translational landslides development evolution of dominant factors and main genetic types of each region.The distribution characteristics of the main two types of landslide are studied.(5)Reveals the relationship between the strike of tension trough and water-flowing joints of structure effect controlling landslide cases and the the evolution of tectonic stress field,distribution characteristics.The study shows the strike of tension trough and water-flowing joints have good corresponding relationship with the neotectonics stress field,in each comprehensive region runs roughly similar.The structural geological conditions of the hydro-conductivity are obtained,which are:(1)The direction of the main pressure stress is almost parallel to the strike direction of joints.(2)When the later stage main stress direction and the strike direction of the joints are almost perpendicular,the historical tectonic action which parallel to the strike of joints should be greater than that of the later tectonic action.(6)Obtain sub-horizontal translational landslides main genetic types which are tectonism leading,lateral unloading leading,vertical unloading leading,interlayer shear zone leading,earthquake factors leading,and reveals the each of the genetic types of evolution and formation mechanism.Respectively take striped shape mountain where Kualiangzi landslide happenned,the valley of Dahe middle school landslide as the prototype build numerical model.Simulate the evolution of the mountain and valley under dynamic coupling process,to verify the tectonism leadingtype and lateral unloading leading type.(7)Based on geo-mechanical model and sliding process analysis,with the application of the conversation of energy law,we derived the theoretical sliding distance calculation formula of sub-horizontal translational landslide.According to the study,the overall distribution shape of uplift pressure under the bottom of sliding body was more close to rectangle,when there are very few groundwater penetration points along the shear outlet.The shape of uplift pressure is more close to triangle,when groundwater is penetrating along most part of shear outlet.Apply the theoretical formula to Shizishan landslide to calculate the sliding distance,and the calculation results showed the good validity and the applicability of the method.The research has some guidance and practical value to prevention and mitigation of sub-horizontal translational landslides.The research reveals that the key factor of the lauching of this kind of landslide is the water head height in the water-storage fractures,the dominant factor which infecting the moving distance is initial width of water-storage fractures and water head height,which is the volume of the water. |
PDF Full Text Request