Cause Mechanism And Stability Study Of Tiansan Landslide Of Kala Hydropower Station In Yalongjiang River

The landslide is one kind of global natural disaster, the hazardous nature is only inferior to the earthquake and the flood. The Yalong River basin took a stave development the key region, has constructed, is constructing, the plan large-scale reservoir has 12, these reservoirs mostly construct in the geological condition extremely complex mountain canyon area.Regarding certain already tended to the stable old landslide, because the reservoir construction will change the geological environment which its original tax saved, caused to have the storehouse shore restoration, even caused the storehouse shore to have the distortion and even once more the jitter glide, for the dam, the storehouse shore embankment as well as the down stream area created the major disaster.The storehouse shore jitter consequence is serious, the light siltation storehouse dam, causes the reservoir the storage capacity reduction, serious even can destroy the dam, spreads the coal life.The giant old landslide as a result of its special engineering geology condition, can have the important influence regarding the dam site choice, even sometimes can play the decisive role.The Kara Hydroelectric power station is located the Yalong River middle reaches, plans to construct the concrete gravity dam, plans to install equipment 1,050,000 kW, the primary election upper, middle and lower three dam sites carries on the ratio to elect. Because the near dam site area will grow 5 giant landslides, the landside mass scale is huge, once jitter, not only will be able to create the reservoir siltation moreover to endanger the dam and other key position construction security.This article depends on " Kara Hydroelectric Power Station in Yalong River Near Dam Site Area (Downstream Water) Landslide Formation Mechanism And Stability Study" the scientific research item, to was located the dam site area the Tiansan landslides to conduct the thorough careful research.The Tiansan landslide is a giant old landslide, the C area grow at present the multi-strip coarsening tension fracture seam, the distortion sign are obvious, its stability has the important influence to the dam site choice.This article based on the open country geological investigation and the full and accurate exploration material, the environment geological condition which saved to the Tiansan landslide taxes has carried on the thorough analysis, the discussion landslide basic characteristic, the research landslide origin mechanism.Uses the quantitative evaluation, methods and so on union qualitative analysis and value simulation, quality synthetic evaluation its stable condition, forecast its trend of development, and to affects the landslide stable sensitive factor to carry on the analysis.Has after swell to the landslide highly and whether the river two questions do carry on the computation analysis, carries on the hazardous analysis in this foundation, and quality synthetic evaluation its project effect.Obtains the main achievement is as follows:(1) Tiansan landslides as a giant old landslide, is two issue of formations.The landslide boundary is clear, after in terrain in front of overall steep slow.The slippery body material composition divides into three: The surface layer slope sediment and the remnant slope sediment (Q₄^el+dl), middle the landslide piles up (Q₃^del) and the base slippery belt.The Tiansan landslide basis engineering geology condition is different, divides into A, B, the C three areas.A, the B area the stability is at present good, in the C area the front part grows at present the multi-strip coarsening tension fracture seam, the distortion sign is obvious, the union distortion observed data analysis, its safety margin is not high.(2) the environment geological condition analysis which saves according to the Tiansan landslide taxes, the Tiansan landslide cause mechanism is slip drawing breakage.Is the Yalong River right bank side slope under a long-term inside and outside battalion of action of force, has the bedding slip to form.The two-dimensional Discrete element calculation result has confirmed its cause mechanism.(3) landslide stability analysis:1) the analysis indicated that, Tiansan landslide A, the B area the stability is at present good.The C area distortion sign is obvious, at present is at the slow change stage, if the C area jitter, has the possibility to form the towable glide, causes the large-scale slippery body jitter.2) Select IV -IV' plane as the computation model overall stability carries on the checking calculation, then carries on the examination separately to various issue of landslide overall stability, the computed result indicated: Reservoir normal operation period, the C area is at the limiting equilibrium condition; Reservoir unusual operation period, the landslide cannot satisfy the standard of security, especially C area.3) the partial stable computation analysis indicated that,Under 1986m store water level normal operation condition, IV—IV The section appears 4 glides to achieve the whole and the partial stability partially.The landslide jitter way is the progressive disintegration: First is the C area appears the jitter, then the B area appears the evolution type to destroy, but the final landslide forms the new balanced body no longer to disintegrate the destruction.4) the value simulation analysis result as a whole conforms to the side slope stress field distribution general rule, also with the limiting equilibrium analytic method analysis result is basic consistent, namely in the Tiansan slippery bodies the front part is at the critical state or the creep strained condition, moreover distorts mainly produces nearby the front part slippery belt.(4) hazardous analysis and project influence appraisal:The Tiansan landslide hazardous natures mainly for the deposition, surge and stream jam, through computation analysis:1) stores water or under the earthquake operating mode, the Tiansan landslides silt up 110×10⁴m³, is opposite in the Kara hydroelectric power station storage capacity, its influence is small.But, the landslide area was apart from reservoir dam recently only 1 km, the massive loose gneiss stack in front of the dam, to safe line of Hong, the reservoir clear silt and the electricity generation facility maintenance still had the noticeable influence.2) the Tiansan landslides under the inpoundment operating mode, have the C area jitter the risk, if C area complete jitter, then in enters the water drop to be highest may cause the 73m surge, transmits reaches 5.9m highly to the under dam site place biggest surge, surpasses the 1991m top of dam elevation, the existence turns the dam the possibility.3) if the Tiansan landslide front part C area jitter, will form high approximately 34m in the Yalong River section the natural pile of fill stone dam, stack dam top of dam elevation 1930m, slightly will be higher than the underground workshop water outlet design flood level approximately (1929.37m), and to the construction period in constructions and so on dam site downstream coffer dam will have certain influence.