Seepage Analysis Of Unsaturated Soil Slope Under The Nonorthogonal Infiltration Of Rainfall Condition

The analysis of slope stability has always been the focus and hot spots in the research of civil engineering and the research on slope stability has been studied extensively and comprehensively.In many engineering accident,slope failure caused by rainfall is very common.There is a very close relationship between the slope failure and the rainfall.Thus,the analysis of the seepage field of the slope is very important.The traditional theory of orthogonal infiltration can not reflect the actual amount of infiltration of rainfall.Most of the traditional commercial software is also codede in accordance with the orthogonal infiltration which maekes users deal with these problems difficulty.This paper introduces the current situation of domestic and foreign research on the problem of slope seepage.The basic theory of seepage,basic equation and the basic concept of unsaturated soil,will be presented.The flow theory of saturated-unsaturated soil is used to analyze the two-dimensional unsteady seepage field.Through the finite element program,the seepage field of the slope is studied,and the distribution of pore water pressure in the seepage field is analyzed,and the law of rainfall infiltration is obtained.According to large amounts of reference,method considering non orthogonal of rainfall was put forward,and the software USNIR(Unsaturated SoilSeepage on Nonorthogonal Infiltration of Rainfall)codede by fortran was used in the analysis of seepage field.Based on the numerical calculation of the examples with USNIR,the effects of the factors such as rainfall intensity,infiltration coefficient,duration of rainfall,slope,soil water characteristic curve and other factors on the unsaturated seepage field are studied.We have made some useful works in numerical calculation.Different from the past,the time step can be adjusted according to the results obtained from the calculation.The seepage field of unsaturated soil is analyzed in detail.USNIR can consider a certain depth of water,and it also consider the situation that there is not stagnant water in the surface of soil especially.The calculation of the matrix suction and return values,the approach can be carried out the value of the infiltration rate dynamically.The following conclusions can be drawn from the analysis:1.At the initial stage of infiltration,the influence of rainfall on soil is very shallow.In the process of rainfall,the depth of infiltration is gradually increasing with the increase of time.The water content of the soil surface decreases,and the infiltration of the soil surface increases with the raise of time.2.When the rainfall intensity is much greater than the saturated permeability coefficient of soil,the soil surface will be saturated.When the rainfall intensity is close to the saturated permeability coefficient of soil,the soil surface is close to saturation.When the rainfall intensity is less than the saturated permeability coefficient,the surface of the soil is in a stable state with a large matrix suction.3.When the rainfall intensity is far greater than the saturation coefficient,the depth of rainfall infiltration increases with the raise of the gradient of the slope in the 30-60 degree.The research results of this paper have certain significant effect on the analysis of the seepage field of unsaturated soil slope under the condition of rainfall.