| The three Gorges Reservoir area is one of the areas with high incidence of landslides in the country.there are a large number of bedding rock landslides in the reservoir area,among which the geological disasters are the most concentrated in Shazhenxi Town,Zigui County.There are a large number of bedding rock landslides near the town.The bedding rock landslides are generally determined according to the relationship between the bedding plane and the slope direction,basically the same or the included angle is less than 30 °.As this kind of landslide usually occurs in three forms of bedding slip,slip bending and collapse bending,there are few researches on bedding rock landslide at home and abroad,and they are mainly focused on the analysis and research of geological genesis.Therefore,the research on bedding rock landslide failure mode and evolution mechanism and early judgment characteristics are carried out,which is of great practical significance to Early prediction,early warning and prevention about the geological disaster of this kind of landslide in the Three Gorges Reservoir area.Based on the detailed field investigation,combined with the comprehensive study of the topography,landform and rock mass characteristics of the landslide area,this paper obtains the geological phenomena in the macroscopic and microscopic aspects of the landslide,analyzes the cause of the apparent sliding of the apparent bedding rock landslide,and infers the genetic evolution of the key control cracks Process: according to the apparent sliding mechanism and characteristics of the apparent dip bedding rock landslide,a three-dimensional limit equilibrium analysis mechanical model is established,and a method of calculating the safety factor by decomposing the movement direction of the Shanshucao landslide and calculating the height of the water head of the horizontal push landslide to analyze the lateral stability of the main landslide body is proposed;a numerical simulation model of the apparent dip bedding rock landslide is established The three-dimensional discrete element simulation of deformation and failure process of apparent sliding of bedding rock landslide is carried out.Based on the analysis and comparison of several typical rock slopes with apparent sliding characteristics,the early identification and feature determination methods of apparent bedding rock landslides are summarized.and provides the early prediction,early warning and prevention of this kind of landslide geological disasters in the Three Gorges Reservoir area Technical support.The main conclusions and achievements of this paper are as follows:(1)Shanshucao landslide in the Three Gorges Reservoir area is a typical apparentbedding rock landslide,but its instability mode is different from the common bedding rock landslide.Influenced by the geological structure and topography,due to the real tendency blocked,it belongs to the special instability mode that the true tendency sliding deformation turns into apparent sliding,and its instability mode is complex.(2)The apparent sliding of bedding rock landslide is controlled by landform,lithologic combination,rock structure,longitudinal crack,rock structure and other factors.The landslide is steep and gentle on the whole,the rock layer of the mountain turns,the front of the mountain is stable,forming the anti sliding section.The "dual structure" of sand mudstone interbedding with soft interbedding,hard and soft on the top,has the attribute of slippery stratum.The formation of mud interbedding The bottom aquiclude forms the base uplift pressure,which also provides a good sliding surface for the instability of the slope and greatly reduces the stability of the landslide;the existence of longitudinal cracks and the formation of lateral hydrostatic pressure by collecting water and forming columns provide the dynamic force for the apparent sliding along the bedding rock landslide;two groups of dominant joints cut the slope,which increases the dispersion of the slope and makes the main sliding body in the process of instability Easy to break up.(3)In view of the key factors controlling the apparent sliding of bedding rock landslides,the mechanism of the formation and evolution of such longitudinal cracks is studied from the aspects of structural stress,evolution of unloading cracks and gravity.The regional prestructuralstress is the prerequisite for the formation of vertical joints of slope,which lays the morphological foundation for the evolution of longitudinal cracks.The river cuts the slope,which leads to the landslide instability of Daling hydropower station.The unloading effect caused by the early stage leads to the formation of longitudinal cracks.Under the action of long-term gravity,the overlying rock mass compresses the soft rock and deforms,leading to the disintegration and tension of the overlying rock mass,which further widens the longitudinal direction The shape of the crack.(4)For the stability calculation of apparent dip bedding rock slope,according to the three-dimensional spatial characteristics of the process of apparent dip bedding rock slope instability,the three-dimensional limit equilibrium is used to calculate the stability of the main sliding mass of Shanshucao landslide as a whole;and considering the composite type of apparent dip bedding rock slope instability,the movement direction of Shanshucao landslide is decomposed,and the water head meter of horizontal push type landslide is used Calculate the height to analyze the lateral stability of the main sliding body.In thethree-dimensional limit equilibrium method,the effect of groundwater is not taken into account,which is equivalent to the natural state.The calculated safety factor is 1.94,which is greater than 1 Considering that rainfall is the key inducing factor of Shanshucao landslide,the horizontal stability of the main sliding mass is analyzed by calculating the height of the water head of the horizontal sliding mass.The result shows that the safety coefficient of the main sliding mass is 0.88,less than 1,which proves that the main sliding mass can produce sliding in the horizontal direction.With the participation of groundwater,the formation of hydrostatic pressure and bottom uplift pressure in the lateral cracks of the main sliding mass can significantly reduce its lateral stability.Hydrostatic pressure provides the dynamic force of the apparent movement of the Shanshucao landslide,thus causing the apparent sliding of the Shanshucao landslide.(5)The results of three-dimensional discrete element numerical simulation show that when the landslide is unstable and broken,the main sliding body of the landslide slides along the direction of true tendency first,then gradually turns to the direction of apparent sliding,and the first displacement occurs at the back edge of the landslide,forming tension cracks.The whole failure process can be divided into several stages,such as starting,right crack opening,front edge shearing,rapid sliding and accumulation.The deformation of slip zone is most obvious in the initial deformation stage,forming shear stress.After the slope rock block is staggered and split,the shear force provided by slip zone is also smaller.(6)According to the investigation of geological causes and the analysis of the instability mode of Shanshucao landslide,it is divided into three stages: initiation,longitudinal fracture development and rapid apparent sliding.According to the analogy analysis of Engineering Statistics and comprehensive analysis of terrain characteristics,lithologic combination,slope structure,dominant joints,inducing factors,blocking conditions and free conditions,six early judging characteristics of apparent dip bedding rock slope apparent sliding are summarized,namely,lithology combination of soft and hard rock layer,steep joint slope structure,true dip blocking,apparent free,sliding creep Longitudinal fracture structure.According to the induced factors,the bedding rock landslides can be divided into three types: rainfall induced type,lower mining type and strong earthquake type. |
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