Experimental Study On Creep Characteristics Of Accumulative Landslide

The accumulative landslide is a kind of geological disaster with wide distribution,large scale,high frequency of outbreak,strong sudden occurrence and great lasting harmfulness.This kind of landslide always happens in the quaternary and modern loose accumulation,whose sliding body material is composed with the secondary deposit,such as colluvial,colluvial deposit,alluvial deposit and colluvial deposit.The landslide of Huahuayanzu in Songxian,Henan province,is a typical accumulative landslide,which consists of macadam soil with high macadam ratios.The landslide slope was damaged by heavy rain.The creep characteristics of the accumulative landslide are of great significance to the early warning and the judgement of the instability.It is meaningful to study the creep test of accumulative landslide slope material.Series of direct shear creep tests on slope material were tested.with the different confined pressure.Through the creep test study on creep characteristics of accumulative landslide,the creep model which is suitable for accumulative landslide and determined the long-term strength was built.The main results were concluded as follows:?1?The tests study on the transfiguration and failure mechanism:the transfiguration and failure mechanism of macadam soil are analyzed by laboratory basic physical property test and direct shear test.The research shows that,in the shear of macadam soil,the particles roll slide and breakage.With the increase of consolidation pressure,the roll and slide ability of particles gradually decreases,and the Scuff marks in the shear planes increases.With the increase of consolidation pressure,the breakage of particles increases,and the large particles'edges and corners breakage develop into the large particles shear.The stress-strain curve changes from weak softening to weak hardening with the increase of consolidation pressure.?2?Direct shear creep tests under different consolidation pressures were carried out,and the creep curves and stress-strain isochronous curves were obtained.Research has shown that,the macadam soil has four stages in the creep process:initial stage,decline stage,steady stage,destruction stage.For each level of horizontal load,initial stage and decline stage occur.When the horizontal load reaches a certain level,the steady and destruction stage will occur.With 100kPa and 200kPa consolidation pressures,stress-strain isochronous curves gradually coincide over time before fourth horizontal grade load.Stress-strain isochronous curves firstly coincide and then disperse over time when fourth horizontal grade load was loaded.The isochronous curve deviates gradually to the vertical axis with the change of stress,and the slope of the curve is gradually increasing.The stress-strain isochronous curves'stress-strain relationship changes from linear to nonlinear.?3?The loading curves were fitted respectively by the Burgers model,the improving Burgers model and Singh-Mitchell model,and determined the parameters of each model.The results show that the element model is better than the empirical model by comparing fitting results.In the destructive stage,the improving Burgers model fits better than Burgers model.The long-term strength of macadam soil is 51%of instantaneous shear strength by stress-strain rate isochronous curves.?4?With the help of FLAC ^3D software,viscoplastic analysis about Huahuayanzu landslip with time considering were done.The results show that,the bedrock in the lower part of the landslide is pressed and a little tensile stress appears in the rear edge of the landslide.Landslide displacement increases with time and tension crack on the back edge of landslide disappear.The back edge of landslide and the middle of landslide has tensile plastic zone.According to the displacement of the monitoring point,the landslide is in the steady and decline state creep stage.