The Stability Analysis And Reinforcement Research Of Deep Loess Slope Under Rainfall Condition

Loess in arid area is usually unsaturated soil,in the rainfall condition,the infiltration of rainwater often lead to slope instability.The reason is that under the rainfall condition,the s slope surface soil water content increases,and the matric suction dissipates gradually,which leads to the decrease of the shear strength of unsaturated loess,and then leads to the landslide.Rainfall is the key factor of landslide and the stability analysis of slope has become an important subject in the field of rock and soil.It is important to research the dynamic change of soil moisture and stability with time and space in the process of rainfall.Based on the saturated unsaturated seepage theory,research the variation of rainfall slope water field,and analyzes the influence of different rainfall intensity,rainfall duration,slope height,slope on loess slope surface soil fissure water content and pore water pressure,and then based on the analysis of transient seepage results,in combination with the limit the balance method analyze the dynamic slope stability,at last design the slope reinforcement with anchor anti slide pile,and then calculate the slope stability after reinforcement.Specific research work is as follows:(1)The basic theory of saturated-unsaturated seepage is summarized.Based on Darcy's law and the law of conservation of energy,the conditions for the solution of the differential equation of saturated unsaturated seepage and the solution of the differential equation are summarized.(2)Considering rainfall conditions,calculate the transient seepage of unsaturated loess,get the result of the change regularity of different rainfall intensity,rainfall duration,slope height,slope and the existence of cracks and fissures in Loess Slope Soil under water field,effects of different rainfall conditions on unsaturated loess the volumetric water content,pore water pressure.From the results we can know: under the condition of rainfall,the rainfall infiltration mainly affected the surface soil slope,the water content of the soil increased,the transient saturated zone appeared,matrix suction(negative pore water pressure)decreased;in addition,although the overall variation of the slope surface soil moisture is increased,the soil matric suction decreases.But the water content and matrix suction change rate and the change range of soil vary with different position,the rate and magnitude of the water content and the pore water pressure changethe of surface soil which is close to the toe is bigger,the rate and magnitude of the water content and the pore water pressure changethe of he top surface soil is smaller.The soil of the foot of the slope firstly began to appear transient saturated zone,with rainfall time increasing,the area extends upward along the slope,and eventually the whole slope surface soil appeared saturated zone.In the process of rainfall,the infiltration rate and depth of infiltration enlarge significantly when the Loess fissures were taken into account.(3)Based on the calculation results of saturated unsaturated seepage,the dynamic change of the safety factor of loess deep cut slope during rainfall is analyzed.Combine the results of seepage calculation with the shear strength theory of unsaturated soil,the limit equilibrium method is used to calculate the safety factor of slope under different duration.From the results we can see: numerical rainfall conditions of different slope safety system is different,the same rainfall intensity,stability coefficient decreases with the increase of time;the same rainfall duration,the strongger rainfall intensity is,the smaller the coefficient is.The slope height increases,the slope surface soil moisture maximum value of roughly the same,but the rain infiltration depth increased with the increase of slope,soil as affected by rainfall to increase,soil shear strength decreases area increases,lead to slope stability safety number decreased;slope increases,safety the coefficient of slope stability;when considering the joint presence,the rainfall process,reduce the safety factor of stability of jointed slope area exist amplitude decreased gradually,which is due to the initial stage of the rainfall infiltration of rain water speed,rate of slope surface soil moisture increased quickly,the late rainfall soil water content increase rate is slow,the slope after 3days rainfall the surface soil is saturated,and the homogeneous slope soil water content increased significantly compared with the difference is not so obvious,so the safety coefficient of slope stability increases speed There was no obvious change in the rate,and the soil on the back slope of 3days did not reach the saturation state.(4)In this paper,the stability of the slope is calculated by using the anchor anti-slide pile reinforcement method and calculated the safety factor of slope stability.The result shows: when anchor is design according to the 15 degree angle with the horizontal plane layout the stability safety coefficient of slope was the maximum;using anchor anti-slide pile to reinforce slope can improve the stability of the slope effectively,although the safety factor of reinforcement slope is also decreased with rainfall,but after 3-day rainfall the y safety factor is still large,so it can ensure the higher stability of the slope.