Stability Analysis Of Unsaturated Fill Slope Under Different Rainfall Intensity

In practical engineering,the stability of slope has always been the hot research direction of geotechnical scholars.Most slope instability usually occurs after seasonal heavy rainfall,and rainfall infiltration is one of the main factors of slope instability.Therefore,the stability of slope under rainfall conditions is concerned by the majority of researchers.Scholars at home and abroad have conducted in-depth research from different perspectives and adopted different methods,and achieved a lot of results.On the basis of the previous studies,this paper combined with an earth-filled slope in Shanxi Province as an example,used finite element calculation software PLAXIS to calculate and analyze the stability of slope before and after reinforcement under different rainfall intensities.The main research contents are as follows: Combined with the characteristics of the high backfill slope in this project and the meteorological conditions in Luliang area of Shanxi Province,the slope calculation model and calculation scheme are established according to the engineering practice.In order to make the simulation results more consistent with the actual situation,the initial matrix suction of the slope was optimized,and then the changes of seepage field and stress field of the slope were calculated under different rainfall intensities before and after reinforcement.The results confirm that:(1)In the rainfall stage,the matric suction on the slope surface decreases rapidly to the minimum value,and the saturation of the soil surface increases rapidly to the maximum value.With the increase of rainfall time,the range of soil saturated zone increases and the safety factor of slope decreases gradually.After the rainfall,the matric suction of shallow soil will gradually recover with the infiltration of rainwater,and the saturation of the surface soil will gradually decrease,and the safety factor of the slope also begins to grow slowly.(2)There is a certain relationship between rainfall intensity and infiltration depth under different rainfall intensity.The greater the rainfall intensity is,the deeper the infiltration depth is,the faster the matric suction of shallow soil within 3m-5m from the slope surface decreases,and the shorter the time it takes for soil at the same depth of the slope to reach the maximum saturation.After the rainfall,the higher the rainfall intensity,the slower the recovery of matric suction of slope surface soil,and the larger the influence range of saturated zone of slope soil.(3)Before slope reinforcement,under the condition of rainfall,the potential sliding surface of slope is usually shallow from the slope surface,showing shallow sliding;After the reinforcement with prestressed anchor cable,the potential slip surface of the slope is the shear port of the sliding surface that cuts into the top of the slope under the condition of rainfall,and the sliding radius is slightly larger than the length of the anchor rod,which cuts out at the foot of the lowest slope,showing a deep slide.(4)The plastic deformation of the slope before reinforcement is mainly sliding towards the side of the slope facing the air under three kinds of rainfall intensity,and the displacement at the foot of each slope is larger than that at the top of the slope;Under the condition of different rainfall intensity,the variation of displacement of each monitoring point with time is consistent.After the slope is strengthened with prestressed anchor,the displacement of the slope is reduced by about 30% under the same rainfall condition,which effectively improves the stability of the slope.(5)It is found that there is a close relationship between rainfall intensity and internal force increment of prestressed anchor cable after slope reinforcement.The greater the rainfall intensity,the greater the internal force increment of slope anchor cable.With the increase of rainfall intensity,the increase of internal force of anchor cable is different at all levels of slope,and the greater the increment of internal force of anchor cable is,and the increase of anchor cable can effectively improve the safety factor of slope before and after rainfall.Therefore,considering the influence of rainfall on slope stability,it is safe and reliable to reinforce slope with prestressed anchor cable.