| The―5.12‖Wenchuan Earthquake induced a kind of shattered slopeswith widedistribution, big potential threats and largescale. Part of shatter slopeswere close to theepicenter or their rock mass integritywerepoor, and the sliding surface were notcompletely connected in the process of earthquake. There was a certain lockingsegment, showing a lag in the main shock landslide; Another kind of shatter slopes asfar away from the epicenter or rock mass integrity was good, often in the post for aperiod of time or even a few years later in the continuous heavy rain under the overallinstability, the formation of landslide, serious difficulties for the prediction andprevention of shatter slopes. This paper takes Wenchuan County FeishaguanLandslide as an example, in-depth study of slope sliding action of seismic shatter.Feishaguan Landslide locate in the town of Mian Si at Wenchuan County, acrossFeishaguan Bridge1#in G213National Highway. The slope instability did notdecline during the earthquake, but it lose stabilityunder the action of heavy rainafterthe earthquake. The volume is about3.72x104cubic metres. Firstly, fieldinvestigation was carried out on the landslide, analyzing the engineering geologicalcondition of landslide, rock mass structure characteristics, landslide boundaryconditions, material composition and so on a series of basic characteristics. Andsampling of rock physical mechanics test, the mechanical parameters of rock and soil,through the analysis of the formation and evolution process of the landslide,formation mechanism and failure mode. Then using finite difference method(FLAC3D) for the whole process of the formation and evolution of the landslide arediscussed in detail, finally analysis of effects of mechanical parameters on slopestability by using the method of limit equilibrium analysis. Through the aboveresearch, the main conclusions are as follows:(1)The Feishaguan Landslidewas stable in the excavation of highway condition,the earthquake was one of the main factors affect the stability of the slope, earthquakeeffect of rainstorm was directly induced failure factors;(2)The landslide area lithology Silurian Maoxian group second group (Smx2),gray green sericite phyllite, sericite quartz phyllite, rock plane occurrence of about260°~262°angle of10°~15°, mainly developed two sets of joints, its occurrencewas L1:320°~325°angle of80°~83°, L2:41°~45°∠61°~66°, which have an adverse effect on stability of the composite intersection L1, L2joints and level ofslope;(3)The average physical and mechanical parameters of rock: rock landslide areadensity is26.03KN/m3, shear strength was C=3.663MPa,=74.74°,31.64MPacompressive strength, modulus of elasticity is2.202×104MPa, Poisson’s ratio is0.2731; the shear strength parameters C=48.24kPa,=44.35°;(4)The failure process of landslide through the front road excavation rainstorm,earthquake and three stages, the failure mode of shear/wedge–thrusting;(5)Analysis of numerical simulation accord with the actual situation: the slope oflarge area plastic failure zone in the earthquake process, but the slip surface is notcompletely through, middle of the slope forming "locking","lock fixed section"strength to support the overall decline in the slope is still in a period of time after theearthquake, the earthquake displacement of slope under rainfall mainly occurs verticaland horizontal;(6)Shear strength of different effects on the stability of slope degree, in seismiccondition and after the storm conditions internal friction angle of influence on slopestability are greater than the effect of cohesion on slope stability;(7)The earthquake caused the attenuation slope mechanical parameters, structureparameters of C into the original67.37%, strength parameters of structural plane is32.63%, into the original55.47%, the decrement of strength44.53%. |
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