| At8:20on11January2013, a large mountain landslide disaster accident happenedat Zhaojia Ditch, Zhengxiong County, Yunnan Province.By the end of12January, hascaused46deaths and two others injured, buried63houses, destroyed over500acres ofarable land, for a total loss of more than45.5million.Relying on the research method of973scientific research project,I participated in the on-site investigation and study of thelandslide, and collect the relevant data.I did systematically research the formationmechanism and accumulation characteristics of the landslide.Mainly acquired thefollowing achievements:(1)Zhaojia Ditch,Zhengxiong county’s landslide is "S" type of irregular shapes,landslide for N45°E are to start the direction, the landslide after the start, quicklyconverted to debris flow, due to the terrain, debris flow happened twice deflection onthe macro.Longitudinal length of about900m, landslide front of about100m wide,landslide in the middle of about250m wide, landslide slip source area of about110mwide, maximum elevation of280m, on the longitudinal slope in the steep-"steep-slow down steep-bottom" characteristics of slope to along with the change of theslope.Deposit landslide area of about1.25×105m2, and the average thickness of about1-3m, accumulation of total volume of about36×104m3, it is medium-sized landslide.(2) Through the field of landform, strata lithology, slope, the structure of thematerial detailed investigation, combined with drilling data, borehole sampling indoorsieve analysis, deposit Zhaojia ditch and complicated structure, stratification, in depositwithin weak interlayer, Zhaojia ditch landslide is sliding along the weak intercalated,weak gravel layer mainly containing fine grained soil, the weak layers make depositwithin soft down hard on the adverse slope structure.In the surface layer of gravel soilof the landslide mass and part for clamping Angle of coarse gravel soil gravel.Slide bed deposit for slide bed, is mainly composed of Angle of coarse gravel figure clip of gravel,underlying rock layers.(3)Zhaojia ditch landslide damage phenomenon is very rich, according to thedifferent landslide damage phenomenon and movement characteristics, landslidezoning can be divided into three zones, namely slide source area, slip accumulation areaand stop into the disaster area.According to the direction of motion of the sliding bodyand accumulation characteristics, and the area A (slide source area) are divied into A1,A2, A3three subregions;B area (slip accumulation area) can be divided into B1, B2, B3,B4, B5five subregion.(4)Zhaojia ditch landslide is in a relatively unfavorable geological conditions,under the continuous rain for a long time, and the role of coal mining, leading to theupper rock permeability coefficient increases, raising the slope underground water levelin the body, with a sudden.Zhaojia ditch landslide slip zone mainly along the depositwithin weak interlayer containing fine gravel soil development, belongs to the weak"and" plane control type landslide, the instability mechanism of creep, cracking-cutting mode, its formation and the damage process can be roughly divided into threestages: the aging deformation stages: glide along the soft layer, squeeze the slopetoe;And the left border cut slope foot-high speed startup stage;High-speed stage offormation of debris flow.(5)Through various physical and mechanical tests: through grain size analysis,according to the results of the sliding body and sliding zone composition is different,slide body denominate is graded gravel, sliding zone of fine-grained soil containinggravel;The permeability of sliding zone is less than the sliding body;By gravel soilmedium shear test found that the mechanical properties of the sliding body and slidingzone have bigger difference, the sliding body is larger than the slide Angle of internalfriction of8.2°, cohesion16.8k pa.Sliding zone full water softening test results showthat with the increase of feed water days, sliding zone each index showed a trend ofattenuation of shear strength, cohesion attenuation amplitude of the internal frictionAngle is big, this is the root cause of the landslide occurred after the persistent rain.(6)Three-dimensional numerical simulation analysis acquires the results: Undernatural condition, the overall stability of slope body and better;After the rise of groundwater level, the maximum shear strain through the whole sliding body, cause theinstability of deposit, the deformation displacement vector of slope direction inconformity with the field investigation.(7)Two-dimensional numerical simulation analysis acquires results: coal and rock permeability coefficient is low, before the bedrock fissure water supply is less,groundwater in the slope body is in a state of a low, stable deposit in naturalcondition.Coal rock permeability increase, after entering the slope increase in thenumber of water, underground water level increased significantly.Zhaojia ditchlandslide continued for a month before the rain and snow, the infiltration side head rise,slope underground water level in the body is in a high state, basic in a saturated state ofthe landslide mass and the slope body material in groundwater under the action of load,the intensity of softening and hydraulic, due to poor physical and mechanical propertiesof sliding zone, weak zone is formed within the slope, so the plastic area of the slidingzone first, and the first to enter a state of yield, but because of the tensile stress, thetrailing edge of slope body and then produce a large number of plastic zone, and fromthe trailing edge of slope body and to the rapid development in the slope body part andpenetration.From the point of the deformation characteristics of slope, the slide bodypresent in the upper slope to reduce the compressive damage step by step in the slopebody part.Groundwater deposit of increasing makes the rear thrust by a growing,eventually leading to slope deposit along with full water weak shear instability. |
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