Research Into Factors Affecting Rainfall Infiltration And Landslide

The dissertation "Research into factors affecting rainfall infiltration and landslide", based on the project of "The effect of groundwater from strong rainfall on slope with vegetation and corresponding response mechanism"(U1033601) sponsored by YunNan-NSFC is intended to look into the factors to affect rainfall infiltration and landslide cases. Focusing on the primary factors such as vegetations and holes in soil and rock that affect rainfall infiltration, It analyzed a host of ingredients that have effect on rainfall infiltration and groundwater seepage in combination with up to date researches done at home and abroad.Taking the following slopes for field study:the basalt slopes of the Maqia-hill in Chenggong college town and Touzhai village in the city Zhaotong, the author has conducted a series of surveys and experiments, such as carrying out field studies on landform, vegetations, holes in soil and rock and slope locale, conducting indoor tests; test of water keeping for the surface of the slopes; locale tests:locale infiltration test, infiltration-trace test, rainfall infiltration observation. Based on the proceeding surveys and experiments, a two-dimensional numerical analysis can be made on slope seepage in terms of MIDAS/GTS.The mainly findings obtained are as follows:l.The contributions of vegetation to rainfall infiltration can be seen on two levels, on the one hand the roots of vegetation greatly increased the number and space of holes in soil and rock located at top layer of the earth’s surface; on the other hand leaves and crown of trees reform also facilitate rainfall infiltration. The channels from root, crannies from the transfiguration and shrinkage of soil and rock, the channel for insects, structural holes in soil and rock...etc. constitute channel of rainfall infiltration and enhance ability of soil and rock to suck in rainfall. But they are located in top layer of the earth’s surface.2.Rock and it’s rotten condition are decisive factors to form structural holes in soil and rock, Structural holes in soil and rock make a great difference to rainfall infiltration, and should be, therefore regarded as key factors in the analysis of the impact of rainfall lead on slopes.3. The characteristics of crannies from shrinkage in soil:(1). The key factors working on crannies from shrinkage in soil are the amount of water in soil、size of soil granules、cycling times from being dry to wet of the soil.(2).A11the chunks of soil formed at the roots、reinforcing effect of roots on soil, together with leaves and crowns help to develop a favorable microclimate to maintain dewiness in vegetation to inhibit the growth of crannies from shrinkage in soil.(3). According to rupture mechanics and stress in soil, the crannies from shrinkage in soil spread downwards and their depth depends on the environment and characteristics of soil. The crannies from shrinkage in soil offer preferential channel for rainfall to infiltrate, but the amount of water infiltrated is limited.4. The crannies from tensile force in soil and rock are large in diameter and go deep down into the interior of soil and rock, which serve as the preferential effective channel for rainfall to in filtrate.5. Some of the may sink along the gradient cover of slope in the process of rainfall infiltration, the amount of which depends on gradient、thickness of seep-layer, modulus of seepage...etc, The diverse geologic sections have different compages of seep-layer with divergent effect on rainfall infiltration. As a result, there are different in the amount of water in soil、modulus of seepage and rainfall infiltration at different positions across the slope(from top to bottom).6. The depth and amount of rainfall to penetrate the cover of the slope have to do with the process of rainfall, the compages of seep-layer and the factors working on infiltration which is omnifarious with hypsography and vegetation as the primary elements.7. As a result of planar numerical calculate simulated seepage of slope, the hypsography and compages of seep-layer can affect the flow of ground-water from rainfall.8. Landslide is a function of a multitude of factors such as interior factors and exterior factors, It has much to with hypsography. At certain level of the slope, unless there are channel for swift rainfall infiltration, the depth and amount of infiltration in a single rainfall is limited, with the result that the effect of rainfall on slope is mainly confined to geological hazards to surface of the slope of the surface of the slope, debris flows. The large-scale landslide at deeper levels is a consequence of long-term gestation of other factors, with the rainfall as activator.These findings can offer academic support for forecast of landslide, and is significant for the prevention and treatment of landslide induced by rainfall.