Anlysis On Characteristics And Formation Mechanism Of The Middle Lower Angle Joints At The Damsite Area Of Maji Hydropower In The Nujiang River

Middle lower angle joint developed as hydropower engineering slope surface, it has important significance in engineering geology of the formation and evolution of the slope and the slope stability evaluation. The middle lower angle joint of Maji hydropower in the Nujiang river have a distinguishing feature of common development 、 great depth and obvious zoning,the formation mechanism and distribution is directly related to the slope stability evaluation and evolution. In this paper, on the basis of engineering geological survey, combined with modern testing technology numerical calculation method, distribution, formation and evolution are analyzed.The specific studies and achievements as follows:(1)Dam site area accounting for almost half of the total number of article fissure in flat fractures, Under the steep slow on form like reverse "八" distributed both of the banks. Angle has a tendency to gradually increase with the deepening of the adit deep.(2)The middle lower angle joints are on the left bank development obviously better than the right,and piecewise development exists with the deepening of the adit deep.(3)The intermittent of the middle lower angle joints are almost short of small.In supergene reformation period the intermittent of the middle lower angle joints are long,but short of small ones in primary stress period are more the in supergene reformation period.(4)The original type of middle lower angle joints are Bai Gang dike section of contact with the surrounding rock.(5)The structure type of middle lower angle joints are “X” Conjugate shear fractures and shear fractures with dipping fault.(6)Supergene type mainly slope gently inclined lateral fissure formation tensile unloading, zhang-shear cracks and trough levels of compression and shear stress concentration produced fissures and exit with form of fracture intensive period in supergene reformation period.(7)Using FLAC3 D software incised simulation valley were using zonal disintegration theory, strain softening model, has been re-distribution of stress field after the cut, pressure-induced crack and valleys foot shear stress slope of focus for the slow pour the main reason for the formation of cracks, and finally with the shear stress increment of the gently dipping fracture disjuncted phenomenon explanation is given.