Finite Element Analysis Of Influence Of Slope-to-Terrace Engineering On Slope Stability In Loess Area Of Southern Ningxia Under Rainfall Condition

Global climate change,leading to large-area landslide of terraced fields on the Loess plateau,has caused a great deal of loss.In order to study the rules of slope stability of terraced fields on the loess terrace banks under rainfall infiltration of southern Ningxia,on the basis of site investigation,the types and cross section of the loess terrace banks parameters of southern Ningxia were obtained.According to laboratory soil test,the loess mechanics and seepage parameters of the loess terrace banks were evaluated.On the parametric basis,the finite element software ABAQUS has established fluid-solid coupling finite element model for slope stability analysis of loess terrace banks under rainfall infiltration of southern Ningxia.Through simulating the slope stability of different types of terrace models(level terrace,slope-separated terrace and original side slope)under rainfall condition,the slope stability of loess terrace banks under the coupling action of different slope pattern and gradient as well as different rainfall intensity and rainfall duration were studied.The research results revealed that:(1)The destruction types of terraces were divided into two forms:one implied that the damage of terraced embankments was shallow landslide,the other indicated the whole landslide of terraced was deep seated landslide.Different types of terraces could only improve the stability of shallow landslides,but they had no significant effect on deep seated landslides.(2)The failure time of terraced of level terrace,slope-separated terrace and original side slope decreased with the increase of rainfall infiltration intensity,which presented a power function relationship.Under the same rainfall infiltration intensity,the destruction time of level terrace remained higher than that of slope-separated terrace and original side slope.There was no significant difference between slope-separation terrace and original side slope.The failure time of the three types of terraced increased with the increase of slope angle forming a linear relationship.The influence degree of the destruction time was as slope angle>rainfall infiltration intensity>terraced slope type.There maintained a coupling relationship between slope angle and rainfall infiltration intensity.The greater the rainfall infiltration intensity was,the more the slope angle was affected by rainfall infiltration intensity.The failure time was gradually weakened by the slope angle.With the increase of rainfall infiltration strength,the failure time became gradually weakened by slope angle.(3)The safety factor of terraced slope decreased with the increase of rainfall infiltration intensity,rainfall infiltration duration and slope angle.The relationship between safety factor and rainfall infiltration duration was quadratic polynomial fitting,and the safety factor stayed linear with slope angle.The safety factors of the three types of terraces were level terrace>slope-separated terrace>original side slope safety factor,yet there was no significant difference among them.The influence degree of slope safety factor was as slope angle>rainfall infiltration duration>rainfall infiltration intensity>terraced slope type.There was a coupling relationship between slope angle and rainfall infiltration intensity.With the increase of rainfall infiltration intensity,the influence of slope angle on safety factor decreased gradually.(4)The horizontal displacement of terraced slope increased with the increase of rainfall infiltration intensity,rainfall infiltration duration and slope angle.The relationship between displacement and rainfall infiltration duration was quadratic polynomial fitting,and the displacement was linear with slope angle.There was no significant difference in horizontal displacement among the three terraced slope types.The influence degree of the horizontal displacement of terraced slope was as slope angle>rainfall infiltration duration>rainfall infiltration intensity>terraced slope type.There remained a coupling relationship between slope angle and rainfall infiltration intensity.With the increase of rainfall infiltration intensity,the influence of slope angle on horizontal displacement became gradually weakened.The results of this study are of great theoretical and practical significance to guide the rational design and construction of slope-to-terrace engineering in loess area of southern Ningxia as well as to prevent and cure geological hazard in loess terrace banks.