Research On The Formation Mechanism Of Longchang Town Collapse In Kaili,guizhou

Around11:30, February18,2013and8:00, February19, the mountain in Chahegroup, Yudong village, Longchang town, Kaili city collapsed on a large scale, whichlocated in Miao and Dong Nationalities Autonomous Prefecture, south-eastern part ofGuizhou province. The disaster resulted in five deaths, buried six houses, relocated21and79.In this paper, geological processes Mechanism-quantitative evaluation ofacademic thinking and systems engineering geology principles guided by the collapseof Long-field investigations and engineering geological conditions related datacollection, data compilation combining indoor, first analyzes the market town ofLong slope characteristics and structure collapse features, the establishment of a longfield collapse " concept model "; formation mechanism and analysis of deep coalmining under conditions of slope collapse through numerical simulation. And for thestress corrosion crack propagation steep near the surface leads to erosion causeddifferentiation intended to strengthen the role of the test, analyze the impact of stresson the differentiation of limestone dissolution rate; major awareness and results areas follows:(1) Longchang Town collapse engineering geological conditions: high steepslope steep Long Course height of about215m,80meters wide,8to24meters thick,the steep slope of85~87°, the cliff face smoother overall, by the same master to thestructure surface. Qixia Formation strata from top to bottom and Maokou limestone,shale and Yao Liangshan Formation limestone shuttle group, which LiangshanFormation shale seams in a folder, so hard down on the gently dipping slope of theoverall slope soft-type structure. Karst is developed upper slope, where there NNE tocorrosion cracks, about60m, higher than the river bottom boundary80~85m; upperand sinkholes connected, but there is still a strong connection with the crest of rock.In the upstream side of the body has collapsed coal mining, upstream coal exportsfrom the main shaft collapsed at the foot of cliffs body90m, mining activity is to cutnearly900m inside the mountain roadway, then recovery, currently exporting Gobhorizontal distance from the cliff500m the mined area18500m2. Gob bottomelevation is570~590m, from the crest elevation220~280m. (2) Collapse damage characteristics: Avalanche deposit of about300,000m3andthe average thickness of the formation at the bottom of the cliff20m, along thelongitudinal length of180m,140m lateral width of the barrier dam, blocking the riverchannel Yudong, formed in the accumulation upstream of the river about200meterslake. According to the different characteristics of the rear wall collapsed, can bedivided into the lower three parts: the collapse of the walls of the Ministry of the highis about40m, before the collapse occurred near the cliff face, the back wall collapsedrock with a strong rock collapsed bridge connection exists; central high is about50m,the collapse of the wall along the dissolution of the most fractured, very small part ofthe rear wall collapse collapse of rock and rock bridge there; lower high is about100m, mainly fresh rock section, indicate at the bottom of collapse, landslide andcollapse the wall rock most connections.(3) Established formation mechanism of Longchang Town collapse "conceptmodel": Longchang Town collapse is in exceptional condition slope structure, inducedby the coal formation. Long steep slopes within the field of high slope gently inclinedramp on the hard under the soft type, the Longchang Town collapse, forming NNEcliffs near the upper surface, the upper and lower ends are connected with the slope tothe dissolution fissures. Slope in coal mining, resulting in upper Gob sinking rockdeformation and pulling the surrounding rock, rock bridge leading to the weakeningof the crest. When the upper rock bridge leading to the destruction of coal mining,slope and then into the progressive destruction of phase instability. Located in asecondary collapse collapsed wall on the left, a collapse occurred equivalent of"excavation" toe, and accompanied by a collision, vibration, etc., leading to thecollapse of rock into the secondary progressive failure stage. After21hours ofdeformation and failure(4) Limestone dissolution law of the Longchang Town collapse, through thelimestone samples for the presence or absence of external loads (ie, low stressconcentration and high stress concentration specimen) commenced dissolution test,the test results were compared. The results showed that high stress concentrationregions dissolution rate was significantly greater than the dissolution rate of low stressareas. Summarize the phenomenon, as inferred stress increases, limestone dissolutionrate will increase.(5) Two-dimensional numerical simulation, carried out with "conceptual model"as the basis to establish a numerical model. The model is divided into eight categoriesmedium. Mined-out area on the left side from the left margin o f about180m, Gobhorizontal length of about193m, a total of32steps according to80%of coal mininggob rate setting. Further analysis showed that:①In the ongoing coal excavation conditions, during the step15, the body ofstress and deformation of slope change significantly, indicating that the slope occursat the local coal excavation impact damage. After the completion of the partial fracture rock bridges, slope vivo distribution of plastic zones tend to be reasonable.②After partial fracture rock bridge, continue ongoing coal excavation, after thecompletion of step29, the slope of the stress and deformation obvious change tookplace, corrosion cracks appeared near the lower end of the plastic zone, indicating thatthe slope experience localized damage, rock bridge further fracture. Further suggeststhat further expansion of the rock bridge, on the slope of the plastic zone in vivoobvious improvement, with the effect of reducing the rock bridge, the plastic zonewill expand. This indicates that the slope into the progressive destruction stage.③Gob completed excavation and rock bridge removed, the slope deformationcharacteristics in vivo display block slip deformation characteristics, cut exportposition above the riverbed about55m. Cut with a dip of about50°. Plastic zoneconcentrated in the vicinity of the lower corrosion cracks, which will occur brittlefailure of rock.