Resaerch On Formation Mechanism And Motion Characteristics Of Lamuajue Landslide In Meigu County

Lammuajue landslide is a typical large landslide which is a slow dip bedding rock landslide, forming the passage of time. Deposit lansdlide along the river is about 10 km, and its vertical length is about 6km, the distribution area of about 20km2, the average thickness of the residual accumulation body about 15 m, the current residual volume reached 3.0 × 108m3.Through field investigation, we found that the mostly of landslide deposit is granular form, and the rock mass has a high degree of fragmentation.In the middle of landslide deposit, slide surface is slow wave. landslide deposit having significant seismic landslide debris accumulation characteristics, however,we observed that the leading edge of stacked body was extending into the vally, like a tongue, and on the west side and trailing edge of the landslide deposit where has a large number of warping rock accumulation which was not disintegration. It has obvious creep-expanding deposition characteristics. These two very different landslide accumulation body shape appear in the same landslide, its Formation Mechanism is unique. Analysis of formation mechanism of the landslide, we can make a new understanding of this massive landslide formation mechanism.In this paper, based on field investigation, we conducted a series of detailed analysis, including landslide structural features, boundary characteristics, deformation and failure characteristics. Use FLAC^3D numerical simulation software to analysis the shress and strain characteristics of natural slope and at the paek groud acculationg of 0.3g, use a discree element numerical simulation software?UDEC? to analysis the formation of the landslide. Get the following results:?1?The slope west border was controlled by two track jiont, the trailing edge was controlled by a steep slope outside joint, these three sets of joints and rock levels together form the landslide slip control structrue.?2?Slope with a special rock structure, the upper rock is hard, sandwiching a layer of soft rock, slope in the strong earthquake overall deformation and failure. Slope geological evolution consists of four phases: Rock unloading,steeply dipping structual surface crack stage; Compression deformation of soft rock, hard rock and fracture the overlying shaped stage; The overall slope instability and failure, blocking river stage; River erosion, the landslide deposit creep stage.?3? Numerical simulation FLAC^3D show: under the natural state, slope deformation weak, there was no stress concentration and penetration of the plastic zone. Under 0.3g earthquake, the slope with the front edge and sliding parts are obvious stress concentration, plastic zone has been concentrated in parts of the sliding zone, which makes the slope has the naterial basis of sliding along the level. under the earthquake, the rock was destroyed by tesion and shear where rock slope surface and the leading edge of slope, and the leading edge of slope deformation greater than other parts.?4? Conduct research on the formation of landslide mechanism by numerical simulation UDEC, the result show that:?1?slope deformation damage earthquake minimum acceleration 0.6g, verall slope deformation and failure of critical seismic acceleration of 1.2g;?2?under seismic action, slope deformation slip band first started from the leading edge location, deformation gradually extend toward the trailing edge, a trailing edge crack band gradulally open, then overall slope sliding along the bottom sliding surface. Slope deformation through four stages:strsee acculation, crack propagation stage?0-6s?; instability leading edge block, the trailing edge tensile failure stage?6-16s?; overall slpe deformation and failure?16-84s?; landslide deposit creep deformation stage. Landslid deposit doesn't completely disitegrated, front deposit clogging vally.?3?After the barried dam being destroyed, accumulation in the valley on the left bank of the loose accumulation of deformation and failure occur immediately, collapsed rock form a second blocking the river. The right bank of acculation deformation relatively weak, only the leading edge of the shacked body local block collapsed.?4? Under natural erosion stage, the leading edge of the stacked body mass flow constantly being taken away, the lesding edge of the slope to maintain good conditions for freedom. Acculation constantly creep deformation, the trailing edge of the slope along the weak levels lateral spreading or slip away.?5?Lamuajue landslide was triggered by earthqueke, landslide deposit experinence long-term creep deformation, eventually forming the current state.