| Rainfall is one of the important factors that cause various geological disasters.Especially,the loess tableland,ridge and hillock provide natural conditions for the geological disasters of loess slope.Through the establishment of indoor loess slope model,the control of rainfall intensity,duration,slope and so on to study the loess landslide process,and the use of moisture sensors,soil pressure box,pore water pressure sensor to monitor the internal parameters of the soil,combined with the rainfall process and the development of slope damage were carried out targeted analysis.At the same time,the numerical model of the same size as the indoor model test is established with numerical analysis software to analyze the changes of pore water pressure,seepage flow and shear strength with the change of rainfall.The main contents or research results are as follows:(1)The development of phreatic line: under the same boundary conditions,40 ° and 55 ° slope model consistent with the law of the phreatic line: during the early period of rainfall,the rate of phreatic line to soil is always kept at 0.11 m / hr.With the rainfall continued,the soil of the surface of the slope is saturating,the slope crest has excess water,the infiltration line of the slope crest and dome of slope rate is reduced,and the hill slope's decline is more serious,the phreatic line passes rate of the slope toe affected by water is greater than hill slope and slope crest.The 40 ° slope model has a faster infiltration rate than the 55 ° slope model.At the same time,the numerical model shows that impact of saturated-unsaturated region boundary is about 5cm on the depth and does not change with the external conditions.The included angl of rainfall infiltration direction and dome of slope at the slope is decreasing,even keep parallel.(2)The characteristics of indoor model monitoring data: Based on the analysis of the monitoring elements in the soil of the two models,and the development process of the slope failure,the characteristics of water content,stress and pore water pressure with different rainfall time are analyzed.(3)The instability process of loess Slope: Rainfall infiltration?The upper soil bulk density and water pressure is increased?The slope crest is softened and internal pore of soil by hole-through slowly and expanding?The formation of through the channel?Slide force is increased and shear strength is decreased?A weak layer is formed along the channel through the pores?Produce damage.Both the 40 ° and 55 ° slope models belong to traction damage caused by softening and collapse of slope toe.(4)The safety factor of the slope has a direct relationship with the rainfall time,it is decreasing with rainfall time in a certain cycle of rainfall conditions.There is a clear cutoff point for the rate at which the stability factor decreases: at the beginning of the rainfall,the rate of safety factor reduction is relatively large,the most dangerous sliding surface is completely in the saturated zone with the duration of the rain,and in the ensuing period,the most dangerous sliding surface is also completely in the saturation zone,the stability coefficient still has the tendency to decrease,but it is relatively flat. |
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