Experimental Study On Two Dimensional Rainfall Infiltration Model In Different Rainfall Patterns

Rainfall is one of the main causes of geological disasters and rock and soil engineering damage.Rainfall landslides have long been the focus of many experts and scholars.Therefore,it is of great practical significance to study the infiltration of unsaturated rainfall.At present,the study on landslide instability induced by rainfall infiltration mainly focuses on the rainfall intensity,rainfall duration,and the aspects related to the nature of the soil and the structure of the rock and soil.There is relatively little research on rainfall patterns.By studying the research results of relevant scholars and the statistical analysis of rainfall-induced landslides,the rainfall pattern is a non-negligible factor in rainfall landslides.By studying the rainfall conditions in the Three Gorges reservoir area,this paper divides the rainfall patterns into five types: incremental,uniform,degressive,middle-large and middle-small.In order to carry out the influence of rainfall patterns on rainfall infiltration,a two-dimensional model of rainfall infiltration was designed and designed.The basic properties of the materials used in the tests were determined through a geotechnical basis test,and the amount of rainfall was determined through a combination of exploration and theoretical calculations.size.Through the physical tests,test data were obtained for moisture content,wet front,and runoff intensity.The GA infiltration model was introduced.On the basis of this,the impact of slope angle on rainfall infiltration process was considered.On the basis of GA model,the rainfall infiltration model existed in runoff was used to infiltrate rainfall.Depth and infiltration rate were fitted and analyzed.The main research contents and achievements of this article are as follows:1)A two-dimensional rainfall infiltration test device was designed and manufactured.The soil samples used in this study were subjected to a geotechnical basis test and analyzed by particle size distribution analysis and liquid-plastic limit analysis.The water content of this test was 8.75% and the corresponding dry density was 1.4 g/cm3.Through exploration and theoretical analysis,the total amount of rainfall is 120 mm and the rainfall time is set at3 h.There are five types of rainfall patterns.2)Slope runoff is a factor considered in this experiment.The law of runoff in the course of rainfall was obtained through experiments.When the rainfall intensity is less than the saturated permeability coefficient of soil,all the rainwater infiltrates into the interior of the slope.When the rainfall intensity is slightly larger than the saturated permeability coefficient of the soil,the slope surface runoff after the formation of the transient saturation area,and the runoff intensity It is stable and limited by the infiltration capacity of the slope surface.When the rainfall intensity is far greater than the saturated permeability coefficient of the soil,the surface of the slope rapidly forms a transient saturation area and the slope surface runoff occurs within a short time,when the rainfall intensity continues Runoff disappears when it is reduced to less than the saturation coefficient of soil.3)Through the TDR moisture sensor,the change rule of the volumetric moisture content during the test test has the following characteristics: From the arrangement of the moisture sensor,when the moisture infiltrates into the sensor sensing area,the sensor reacts quickly and in a short time When the moisture content reaches the peak value,the water content slowly decreases when the rainfall ends,and the moisture content decreases slowly in the observation time range.When the initial rainfall intensity is high,the response time of the moisture sensor is short,indicating that the water supply is sufficient at this stage and the infiltration rate is fast.4)Under different rainfall patterns,the changing patterns of wet fronts are also different.Under the same rainfall conditions,the depth of infiltration at the foot of the slope is the largest.Through the analysis and comparison,the rainfall pattern with the largest infiltration depth is the middle and large,and the infiltration depth is the smallest,indicating that the infiltration depth is related to the saturation time of the surface soil.The shorter the time to saturation,the earlier the infiltration capacity is controlled by the infiltration ability of the soil itself.The changes in depth have also been affected by various factors,and are also strongly related to the degree of compaction of the soil filling and whether the soil is homogeneous.5)Based on the Green-Ampt infiltration model,the Green-Ampt model considering the effect of slope angle was deduced,and the rainfall infiltration model suitable for this condition was obtained.The model shows that when the rainfall intensity is small,the slope angle has little effect on rainfall infiltration;the greater the permeability coefficient,the more likely the surface soil becomes saturated,and the speed of the wet front is fast;when the permeability coefficient is small,the surface layer The soil is easy to saturate and the wet front is slow to advance.When the rainfall intensity is constant,the infiltration rate tends to decrease slowly with the rainfall,and finally stabilizes.Through the infiltration model,combined with the parameters obtained during the experiment,the infiltration rate and the wet front depth within the rainfall time period were fitted and analyzed.The depth of the final fit was not different from the depth of the wet front observed during the test.The model is very adaptable to this test and can describe the rainfall infiltration process.