The Research Of The Formative Condition And Instability Mechanism Of The Landslide Controlled By The Key Blocks In Southwest Mountainous

June 5, 2009 at 3 PM, a superlarge landslide about 500 million m3 of volume happenedat cocktail mountain in iron township WuLong chongqing China, despoilled the life of 74compatriots, and give local huge economic losses. In China's southwest mountainous area(such as chongqing, sichuan, guizhou and guangxi), widespreadly there are many mountainswhose geological conditions and slope body structures are similar to the cocktail mountainlandslides or chain-cliff dangerous rocks in The Three Gorges. In WuLong iron ore townshipnear, there still exist many place whose geology,terrain conditions and mining activities aresimilar to.the cocktail mountain. Superficially ,the flood-gates modes of such landslides ismainly that the dangerous rocks collapse towards lateral steep cliff, but in truth there arepotential pitfalls of large-scale landslide. This kind landslides controlled by "key blocks" arecharacteristic by"recognition is difficult, with intense concealment; The complex formationmechanism is put in bigger dispute; Inundated mode is strange and difficult, with high risk ofpreventing or reducing the disaster"This paper ,the cocktail mountain landslide in Chongqing Wulong for example,willresearch the formative condition and instability mechanism of the landslides controlled by thekey blocks. Therefore,I have done the detailed engineering-geology survey in headwater areaof the sliding, collected rock samples from several characteristic parts of sliding source,anddone a variety of testings of physics or mechanics and measuring-age .Also I have decoratedgeophysical exploration work for landslide accumulation area, and basicly understood thedistribution characteristic of landslide accumulation area.In addition, I have carried alandslide stability of three-dimensional physical simulation and 3d limit equilibrium analysis.The physical simulation model is characteristic by"long 2.9m, width about 1.6m, high about1.9~3.5m, volume about 12m3,about 6,500 pieces of rock, the total weight over 200 tons". themain research results as follows are concluded from This article: (1) the cocktail mountain landslide is a landslide by rheological control. Beforedestruction, its " separate interface" are already clear: the east is a free face of steep cliff; inthe southern there is a T0 crack about 4.1 to 13.9 million years; in the west there is a T1 crackabout 2.6 ~ 5.3 million years ago;in the north there is a very broken karstic zone; at the steepcliff central there is a relatively flat slope zone for a potential sliding-surface.(2) Two groups of steep-sloping, orthogonal joints cut cocktail mountain rock intoinnumerable hexahedral huge rock-block, the "overhead structure"of building-block body iswell discrete, and reduce the mountain's overall stability.(3) Karst largely contributed to the formation of landslide: (1) for the influence karst, therock is broken ,long-term creep deformation, and provides a extrusion space similar to"freeface"for long-term creep deformation. (2) the rock show "the column" shape in karstic zone,the overall shear capacity is low, the rock's in north-east more particularly low ,and provides acutting-out space for the last destruction,(4) the key block are composed of limestones and gravel-shape limestones, the latterprovides the main resisting-slide effect. Key blocks in plane is a triangle area,in the process ofvermicular sliding,the countersliding effect are showed by the transverse-locking function innorth-west side and the stopping- cutting-out role in the north-east side(5) the cocktail mountain landslide has a sliding-interface, above whom there is aharder,floods gravel-shape limestone,under whom there is a soft,water-proof carbon shale.These two stratigraphic lithology features are very different, provides a material base for thesliding surface.(6) the slipping-bed consists mainly of carbon shale ,who has a obvious characteristic ofcreep.as the building-blocks long-termly peristalsis along the top of the carbon shale ,theshear capacity on sliding-surface gradually become the long-term strength.(7) by physical simulation,combining the investigation of the similar mountain wholocate on two flanks of the cocktail mountain and are exploited for ore .It's found that:themined-out area , often produced a deformation as "sinking", however, it promotes andaccelerates the formation of cocktail mountain landslide(8) based on the three-dimensional stress limit equilibrium analysis, only when thelong-term strength parameters of sliding-surface are adopted, the slippery body will entervermicular slippery stage.(9) the cocktail mountain landslide is a typical landslide controlled by the rheological,the process of deformation and failure is that"emerging T0,T1 separation cracks"â†'"firstlyvermicular slipping along the true Dip direction"â†'"squeezing the T1 crack"â†'"Cuttin thelocking- segments at T1 cracks"â†'"Redirection then squeezing karst zones"â†'"Cut the keyblocks northeast corner"â†'"geological disasters of 6.5 cocktail mountain landslide"。...