The Investigation On The Effect Of Rainfall On Pore Water Pressure Within Unsaturated Soil Slopes

The investigation on the relationship between the stability of unsaturated soil slopes and rainfall mainly focuses on the effect of rainfall intensity, duration and rainfall amounts. But, the effect of the rainfall pattern on the stability of the slopes is considered very little. Currently, when studying the effect of rainfall pattern on the stability of slopes, the effect of the rainfall pattern's uniformity on the stability of slopes are studied mainly, in the condition of supposing ideal columnar rainfall pattern distribution. However, during the actual rainfall course, the occurrence numbers and moments of rainfall peak are very important to the forecast and prevention of landslide. Therefore, the effect of the occurrence numbers and moments of rainfall peak on pore water pressure within unsaturated soil slopes are investigated. The main research content and result are as follows:1) The two-dimensional governing equations for steady-state flow and transient flow are derived based on unsaturated soil mechanics. Then, the transient flow is modeled by SEEP/W software, and some advices when the transient flow is modeled are brought forward.2) Assuming antecedent rainfall distribution pattern during a long-term rainfall, the pore-water pressure within unsaturated soil slope are calculated by the finite element method under boundary conditions and rainfall boundary conditions. The results of the numerical analysis show that the ratio between rainfall duration and rainfall stopping duration can significantly influence the change of pore-water pressure within an unsaturated soil slope. If the rainfall duration is almost the same as rain stopping duration, the more intensity and duration of every rainfall event, the larger change of pore-water pressure.3) The rainfall intensity formulation is identified, and according to Keifer&Chu rainfall pattern's principle, the intensity of different rainfall time can be calculated. Then, the numerical seepage analysis can be carried out with different r under different soil hydraulic prosperities and initial conditions. The results of numerical analysis show that the parameter of rainfall peak r can significantly influence the change of pore-water pressure. For Keifer&Chu rainfall pattern, when the rainfall duration is less than 12 hours, the difference...