Layer Slabbing Effect On Deformation And Failure In Consequent Rock Slope

As a type of rock mass with widely distributed on earth,the stratified rock mass has the characteristics of good layering,strong anisotropy and great influence on the change of the existing environment,which brings many problems to the engineering construction.At present,the research on the slabbing of stratified rock mass is generally focused on the slabbing of the side wall rock mass encountered in the development of underground engineering,and there is little research on the slabbing of the slope engineering.In this paper,the stratified rock mass in the dam site of the Yellow River Hydropower Station in the Cihaxia Gorge is used as the object.Through the field survey and statistical processing,the variation law and mechanism of layer thickness caused by layer cracking are revealed.Based on this,the influence of the layer cracking effect on the deformation and failure of the stratified rock slope is explored by the No.3 landslide in the dam site area.This paper enriches the theoretical study of bedding rock slopes and provides reference and theoretical basis for engineering construction schemes.The main findings are as follows:(1)The slabbing of layered rock mass is affected by lithology,unloading,weathering,tectonic action and its comprehensive effects.For the river bank slope of the river,the unloading effect has the greatest extent.The layer thickness of the layered rock mass in the bank of the river is positively correlated with the horizontal buried depth and the vertical buried depth due to the layer cracking,that is,the layer thickness oscillating increases with the increase of the buried depth,and layer cracking will be more pronounced with influence with the techtonic movement and weathearing.(2)Based on the investigation of deformation and failure characteristics of the site,it is concluded that there are two types of buckling,the single level buckling and multi-level buckling,and the theoretical calculation method is used to calculate the landslide collapse,and the thickness of the layer and the critical length of buckling are took into account.The relationship between the two type was analyzed.The buckling deformation generally consists of two parts,that is,the upper drive section has a sliding surface that slides downward,and the lower flexure section collapses in the free direction.In the bedding rock slope,the cracking of the rock mass layer leads to the thinning of the rock layer,which weakens the buckling resistance of the rock plate and reduces the critical buckling length of the slope,thus promoting the occurrence of the buckling.At the same time,the shear stress formed during slide of rock stratum and buckling further exacerbates the slabbing.(3)The numerical simulation method was used to analyze evolution of the slope,and the unloading action and layer slabbing of the river undercut were taken into account in the simulation process.The analysis shows that the hard rock slopes such as sandstone slopes generally undergo single-level buckling,while the rock strength is weak,such as slate slope,multi-buckling buckling may occur.The slate is sensitive to unloading and weathering,and its stratification causes the surface rock mass to be thinned,resulting in multiple collapse of the surface rock.With the continuous occurrence of the collapse,the surface rock layer is gradually cut off and peeled off,and then a new collapse point is generated in the fresh exposed rock layer,which makes the slope deformation and destruction have gradual,inheritance and endlessness.