Research On Failure Mode And Stability Analysis Of The Slope At Lenggu Hydropower Station On Yalong River

Hydropower Station of Lengu on Yalong river in Sichuan Province Ganzizhou yajiang river mainstream, reveal the site of factory area line area for petroleum exploration at present stage of development along the river is about 800 m long cataclastic rock mass structure, performance for the river fracture common open, rock mass unloading is strong, and a high degree of fragmentation, superficial department skid collapse. Find out the boundary conditions of fractured rock mass structure, distribution range, its deformation characteristics and failure modes, and then evaluate the slope stability under various working conditions, is of great significance to the late workshop excavation construction, at the same time of high geostress deep canyons of slope rock mass deformation and failure mechanism research has certain theoretical significance.This article through the field surface survey, drilling, logging, and adit logging, acoustic test, in-depth study systematically the structure features of the slope rock mass and its deformation phenomenon, established the geological mechanics model of slope rock mass deformation and destruction. On the basis of further analysis of slope stability by using numerical simulation software, the specific contents and results are as follows:(1) Yanchang formation lithology of slope rock mass system on Jurassic bonobo group metamorphic sandstone, the main development in the three groups of steep dip Angle structure plane and a set of slope surface.slope, surface structure, joint fissure intensive development, small fault, extrusion fracture zone are widespread, rock mass structural plane cutting common cataclastic structure and pattern structure, the stability of surrounding rock, poor ability of adit expose existing dump deformation of rock mass, loose and broken open and dislocation, much has been raised and collapse phenomenon.(2) No regional fracture in the study area(grade I, II) structural surface through, only developing scale ranging from small faults, extrusion fracture and fracture zone and growth of dike(quartz vein, calcite vein), with III1, III2, level IV structural plane is given priority to, the surface of the rock mass quality classification the whole slope rock mass is given priority to with grade IV, V, local position class III rock development.(3) According to the adit exploration and field judgment, common development of deep rock mass fracture structure, especially in shallow depth of 40 m is broken, loose rock body as a whole, since the steady ability is poor. In the slope height about 0 IV ~45 m section, rock mass is relatively loose, cataclastic structure, by random joints and cut into the stone of the development of intensive and to adit deformation damage is very serious. Once in the corner cut excavation depth scope, it is likely to have a massive collapse. And 45 meters deep, rock mass structure, there exist certain differences with cataclastic structure ~ Mosaic structure is given priority to, local time, block structure, which near the fault extrusion with more development sites, and shows the characteristics of fragmentation, 100 meters after the rock mass quality tends to be in good condition, but most adit not expose, according to the laws of the rock mass unloading development combined with borehole data of part that cataclastic structure rock mass level boundary in roughly two hundred meters depth development, integrity, a good block structure exposed rock depth can’t more than four hundred meters.(4) According to its broken open, joint dislocation, the overhead of rock mass, high strength, low wave speed of rock mass, the rock in deep rock mass unloading and stress release etc, could be divided into: the cataclastic rock type unloading damage type, fault type, joint fissure control, dumping, study the forming condition of each type, characteristic and performance combinations.(5) According to the characteristics of the deformation of slope rock mass fracture combined with the analysis of characteristics of rock mass structure and slope landforms, established the natural slope and engineering slope rock mass deformation and failure mode, of which natural slope instability destruction is divided into superficial department:(1) colluvial deposit, loose rock superficial skid destruction;(2) structural plane intensive cutting forming block instability; The failure mode of slope: slip shear failure; Engineering slope failure mode are: controlled by fault or grow up structural plane skid and landslides.(6) The 3D numerical simulation of landslides and heavy rains natural conditions(FLAC3D) stress and deformation characteristics are simulated, the result shows that:(1) natural slope deformation under the condition of working condition of the scope and the deformation of the heavy rain, heavy rain when the displacement value of the largest in table close repose of structure of rock mass.(2) the plastic damage area, mainly in low elevation colluvial deposit and its blunt Gou Gou shore, and the distribution range is relatively scattered, main show is destroyed, local shear or tensile shear failure. Deposit(3) natural landslides and heavy rains condition and does not appear through the higher shear strain and the plastic damage area, the whole stability is good, but in the abrupt change in topography and the physical and mechanical properties is poorer parts of the rock mass displacement and plastic zone, which may produce small collapse and slide collapse destroyed.(7) Overall in the condition of excavation, slope deformation damage obviously in the slope, the slope to the weak structure plane with steep dip weak structural plane, and cut the locking section in the sliding surface, eventually make the slope instability, using state of the software can simulate the whole failure process, the results showed that the divided into three stages: 1) deformation start development stage;(2) all of a sudden failure stage(3) stage of sliding instability. Although nearly symmetrical dispersed structure of rock mass slope is mainly composed of rupture, but its overall damage levels still suffers Ⅲ structural plane or Ⅳ structure level control.