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Research On The Formation Mechanism Of Loess-mudstone Landslide Through Numerical Simulation

Posted on:2015-03-02Degree:MasterType:Thesis
Country:ChinaCandidate:C LeiFull Text:PDF
GTID:2180330422485490Subject:Geotechnical engineering
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Located in the southeast of Gansu Province,Tianshui is a typical valley city,With theinfluence and control of topography,geological structure, soil properties and rainfall, Thelandslides there,which are usually more particular, have a huge impact on influenced thedevelopment and the daily life of the region. So it is important to study the mechanism oflandslides there. This paper selects a typical landslide in Tianshui City:loess-mudstonelandslide, focusing on the analysis and studies of the failure mechanism. It aims to provideservices for the engineering design, and to provide material for further study of suchlandslides.Geological structure of the landslide zone is composed of Quaternary loess andCretaceous mudstone, a typical feature slope of "double heterostructure" structure, the gradof which is about25. Above all, the abundant rainfall is also one of the external factors.The study shows that the landslide is medium-sized loess-mudstone bedding landslide andthe sliding surface is loess-mudstone interface and sliding surface are controlled by strataoccurrence. The inclination of sliding surface is about8°. The stretch-pulled surfaceformed by the loess of landslide trailing edge is steep and presents a slip-cracking failuremode.Through the shear texts and triaxial texts, we come up with the variation of c、: withthe increasing of water content,the friction c and the cohesion decreases. When the watercontent is less than18%, the cohesion c is reduced greatly, When the water content isgreater than18%,change in the cohesion c lesser extent. Meanwhile we study therelationship of stress-strain under the effects of different confining pressure (50kPa,100kPa,150kPa,200kPa,250kPa,300kPa,350kPa,400kPa,450kPa and500kPa) and the samewater content (20%) and different water content (10%,12%,14%,16%,18%,20%,22%and24%) and the same confining pressure(50kPa,100kPa,200kPa and400kPa). Whichshows that with the increasing of water content,the relationship of stress-strain varies little.That is when the confining pressure is less than150kPa, the curves show a weakening type; when the confining pressure is more than150kPa, the curves show a hardening type.Through4groups of Seepage tests, we draw a conclusion that the permeabilitycoefficient of the Malan loess in the landslide is2.26m/d. The permeability coefficient ofthe artificial rolling soil is0.23m/d, and0.91m/d is the broken mudstone. It shows that theinfiltration of surface water play a decisive role to produce the entire landslide.After sliding, we draw maps of one plan view (1:1000) and three profile view (1:500).Using the Surfer software to restore the slope before sliding(1:500),we finally transfer it toFLAC3D and build the simulated three-dimensional model.Through the analysis of engineering geology,the deformation evolution mechanismof of loess-mudstone type landslide are proposed: peristalsis-pulling cracks, slip–disintegration, cut-out. Based on FLAC3D numerical simulation, we analyze thecharacter of stress-strain and the formation mechanism of landslide, namely the landslideslip to the slide. Comparing with the facts, the results are basically consistent. Finally weanalyze the process of the landslide, namely easing and low effect, showing sliding slowand little.
Keywords/Search Tags:Tianshui City, loess-mudstone landslide, physical and mechanicalparameters, FLAC3D numerical simulation, the formation mechanism, the process ofevolution
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