Stability Prediction And Deformation Mechanism Of Typical Rainfall Landslides In Wudu Area,Longnan

Rainfall-induced Landslide is one of the most frequent landslide types in nature.Wudu area in Longnan is one of the areas with the most rainy landslides in Gansu province and the whole countryLoess-mudstone landslide and phyllite residual-slope accumulation horizon landslide are the two most widely distributed landslides in this area.Typical representatives of the two types of landslides in Wudu area are Haojiagou Landslide(Loess-mudstone landslide)in Berlin Town and Lengganliang Landslide(Accumulation landslide)in Liangshui Town,which were selected as the research objects.The SEEP/W,SLOPE/ module in GeoStudio and FLAC-3D software were used for coupling analysis,which is based on the step-by-step coupling approach of rainfall infiltration and landslide deformation.The stability trend and deformation mechanism of landslides under different rainfall conditions were analyzed.The main results are as follows:Variation of seepage field and stability trend of landslide between Lengganliang and Haojiagou landslide under different rainfall conditions.Bishop method and m-p method are used to calculate with the whole and local stability state of landslide.Under the rainfall conditions of 52.3mm/24 h,72.3mm/24 h and 92.3mm/24 h,the Haojiagou landslide is generally in a basically stable state,with local deformation failure,and the failure position is in the middle of the landslide.Lengganliang landslide is in a basically stable state as a whole under rainfall conditions of 82.2mm/24 h,102.2mm/24 h,122.2mm/24 h as well as local deformation failure,which is located in the central and posterior areas of the landslide.At the same time,the Haojiagou landslide,Lengganliang landslide as a whole start critical rainfall,and compare with the size of the critical rainfall of two landslides,analyzed the size of the reasons.The calculation results of landslide stability under rigid body limit equilibrium have limitations and cannot demonstrate the failure process of landslide from stability to instability,so the finite element software flac-3d is used to respectively simulate the ways of failure and deformation of Haojiagou landslide and Lengganliang landslide under critical conditions.The shear strain increment,displacement change and plastic zone change of three dimensional slope body and two dimensional main section are obtained.The distribution of stress and strain,the maximum position and displacement of slope deformation and failure,and whether the plastic zone is connected are pointed out.The similarities and differences of the deformation and failure characteristics of the two landslides are compared,and the causes of the similarities and differences are briefly analyzed.