Formation Mechanism And Stability Calculation Method Of Loess Collapse

Loess is a porous,weakly cemented,and unsaturated Quaternary sediment deposited in arid and semi-arid regions by the wind.It is widely and thickly distributed in China,making the Loess Plateau the largest bulk accumulation of loess on the Earth.Shanxi province is located in the middle east coast of the Yellow River,west of the North China Plain,which is a typical mountain plateau widely covered with loess.With the rapid development of economy in Shanxi Province,human activities such as building highway and railway,mining,building and filling in the ditch continue to increase,making the loess collapse of geological disasters occur frequently,which threat to people's lives and property in varying degrees,and adversely affect social stability.Based on the investigation of geological disasters in Shanxi Province,a large set of data is obtained from the 194 loess collapses.In this study,the internal and external causes of collapse failures are summarized based on the statistical analysis.Emphasis is given to the influences of loess property,slope features(i.e.,slope type,gradient,height,and aspect),rainfall,freezing and thawing,and human engineering activities.Based on the existing research and field investigation,the failure modes of loess collapse in Shanxi province are summarized as follows: spalling,sliding,falling,toppling,cracking-sliding and caving.In this paper,the formation mechanism and development characteristics of these six types of loess collapse failure modes are summarized.Based on the data of field investigation,this paper summarizes the relevant laws about the relationship between the width,the depth and the extension direction of the shear wall and the type,the development stage and the size of the loess collapse.It has a more profound understanding of loess collapse.The toppling collapse and sliding collapse are the most important developed types in Shanxi Province,so this paper carries on the stability calculation formula in view of these two types of collapse.Considering the vertical and inclined collapse back wall,taking into account the effect of water pressure on the slope,the moment equilibrium and the force balance equation of each collapse model are established respectively to solve the corresponding minimum safety factor.The maximum shear stress,the minimum principal stress and the horizontal displacement are analyzed by using ADINA software.The change of stress and horizontal displacement of loess slope is calculated from the joint development to the collapse,which shows the formation mechanism of the loess collapse.