Numerical Simulation Of Slope Rainfall Infiltration Vegetation Development

In recent years, landslide disaster caused by the heavy rainfall is more and more serious.The study of rainfall infiltration on the slope is significant for the research of the entire developmental process of landslide. This article selects two typical vegetated slopes, Chenggong Duanjiaying test area and Zhaotong Touzhai gully test area. The measure of moisture content and soil particle composition, dye tracer test and double ring infiltration experiment in the test area by carried. The experimental data as the parameters required in the numerical simulation. The existence and geometric shape of the macropore, rainfall conditions and initial soil moisture content influence the rainfall infiltration. The numerical simulation of the factors influencing the rainfall infiltration of the vegetated slope soils accomplished through the HYDRUS-2D model. To analyse the results of numerical calculation and draw the following conclusions:(1) The presence of macropore in vegetated slope soils accelerates the vertical rainfall infiltration; slows down the underground runoff of topsoil; delays the presence of the transient saturated zone of topsoil and leads to the irregular shape of the wetting front. And when the diameter of the macropore increases, the preferential flow velocity decreases, macropore hydrops response time (slightly) delays, and pressured infiltration area increases with the hydrops in the macropore dissipating more quickly;(2) while with the increase of the length of the macropore leads to more the curvature, the deeper rainfall infiltration depth, the longer delayed hydrops response time at the bottom of the macropore, the lower height of the hydrops in the macropore and without significant effect on preferential flow velocity however. If the curvature increases, the changes are as follows: the hydrops response time in the macropore first increases and then decreases; the vertical rainfall infiltration depth reduces; the height of the hydrops in the macropore increases; the maximum velocity of the preferential flow first increases and then decreases; the effect of the curvature on the wetting front is mainly in the early stage of rainfall and the irregular shape of the wetting front reduces with the increase of curvature;(3) With the increase of macropore group density, the shape of the wetting front is more complex and the rainfall infiltration is faster when the hydrops response time of the macropore is slower and the interaction among the macropores is greater. As the intersection angle between macropore group axial and the slope orientation reduces, the irregular shape of the wetting front reduces in the slope and the maximum velocity of the preferential flow increases. When the macropore is located in the topsoil and the macropore axis is approximately parallel to the direction of slope, macropore flow may overflow surface to generate a return flow under high rainfall intensity, which is to the disadvantage of rainfall infiltration;(4) Under the condition of the same rainfall intensity and rainfall duration, the larger of the rainfall density, the larger is the change of the moisture content in the slope soils and the faster is the rainfall infiltration velocity. With the same rainfall pattern and rainfall intensity, the longer the rainfall duration, the larger is the increase of the rainfall infiltration moisture content and the deeper is the wetting front though not significant, while the change of the moisture content in slope soils of the progressive increased rainfall pattern is the largest and the change of the moisture content in slope soils of the progressive decreased rainfall pattern is the smallest with the rainfall density and rainfall duration. In the case of other conditions are exactly the same, the larger the initial moisture content of the slope, the deeper is the rainfall infiltration depth and the faster is the infiltration velocity and the wetting front migration velocityafter the rain infiltrates into the soils.