Instability Mechanism Of Low-angle Layered Slope In Weining Area Of Western Guizhou Province

Six middle-small rocky landslide occurred in Zhaojiashan area in Weining County of Guizhou Province. The composite layered slope structure is sandstone mudstone of upper Liangshan group conglomerate and limestone of the lower Maping group. Normally stable slope has occured a series of landslides, is what causes landslides occur? This kind of landslide in Weining area has certain representativeness, so its control factors and the study slope instability mechanism has the practical significance. In this paper, based on field geological mapping and in combination with drilling, laboratory test data, reveals the basic characteristics of the landslide group and typical landslides, this kind of control factors of landslide formation are analyzed, and select Yinmatang landslide as the main object, analyzes its deformation failure mode, use of 3DEC simulation and movement process of the landslide deformation and destruction. Main conclusions are as follows:(1) Landslide group in the study area are mainly distributed in Zhaojiashan area, a total of 6 similar development of small and medium-sized landslide, slide body thickness of 3.4~3.4m. Slide body composition of gravel soil, quaternary loose bed, and a small amount of cataclastic rock mass; Sliding surface are the interface of strong weathering-weathering; The nature of the landslide is the landslide of the rock landslide. Landslide affected by karst development main sliding direction and form, its development strength degree boundary conditions play a role in control of landslide.(2) The slope composed by the upper Liangshan group sandstone mudstone and lower Maping group thin to medium thick-bedded limestone. Study area near NW trending towards rock, occurrence 55°~72°∠17° ~ 22°. Six landslide original slopes before sliding are low-angle layered slope, where Yinmatang landslide and 4# landslide are reverse slope, 1#, 2#, 3# landslide are oblique slope, 5# landslide is transverse slope. Sandstone of Liangshan group strength high, is a hard rock group developed two steeply dipping joints, occurrence was 135° ~ 180° ∠ 67~86°, 258°~302°∠74°~88°; Mudstone of Liangshan group strength low, is a soft rock, easy to soften water disintegration; high-level group of horses limestone strength, is a hard rock. Study area Liangshan sandstone, mudstone rock quality is poor-poor, poor horse weathered limestone rock group level quality.(3) The main role of groundwater slope: ① Soften the structural plane and the mudstone layer, and lubrication; ② For the karst provide the necessary conditions. Maping group limestone karst development degree is high, the limestone dissolution "concave cavity" structure formation, international airport for landslide formation conditions, differences in corrosion control effect for the landslide boundaries, and the landslide deposit thickness, such as morphology has great influence. Both effects lead to construction and weathering rock surface structure is more developed, and further undermine the structure of the slope, very broken rock, promote karst.(4) According to Yinmatang landslide formation evolution analysis, it can be divided into: ① Liangshan group mudstone layer at the bottom of the softening stage, ② Karst preliminary development stage, ③ Through slip plane formation stage, ④ Integral sliding failure ~ accumulation stage. Landslide deformation and failure mode to fall to collapse and slide slip to cracking type combination mode, according to the mechanical condition classification belongs to pull-type landslide.(5) Through the finite element numerical simulation software to Yinmatang landslide evolution process modeling of four phases,, it is concluded that the bottom of the slope in front of the weathering dissolution and liangshan group mudstone layer bate denudation stage in a stable state, and well versed in stage of formation of sliding surface slope is in unstable state, convergence, and the final phase slope calculation results did not obtain the stability coefficient of slope has been damaged, produce plastic deformation.(6) Using 3DEC discrete element software to simulate the deformation and failure process of Yinmatang landslide, the deformation and failure-movement process is divided into four stages: ① rainfall induced landslides startup phase; ② landslide overall speed sliding stage; ③ Leading edge accumulation stage; ④ the overall accumulation to slope stabilization stage.