The Contribution Of Soil-Root Interstice To Rainfall Infiltration In Soil Of Well Vegetated Slope

Rainfall infiltration is the main inducing factor of the unsaturated soil slope instability in nature, and there is a close relationship between rainfall and landslide.Since the middle period of last century, it is showed by the statistics that the frequency of instability events of vegetated slope is higher and higher under the action of heavy rainfall, which not only damages to the local ecological balance, and disrupts people’s normal life rule, but also poses a serious threat to the people’s life and property safety. With the continuous development of social economy and regional infrastructure construction, the problem which involves in the slope stability have caused more and more attention of the engineering. However, it is not enough that only consider the study of vegetation slope and shallow stability under the condition of rainfall. As the vegetation development, this article choose the slope in Touzhai of Zhaotong, Duanjiaying of Chenggong and Xiangchong of Gejiu, Yunnan province as the research object, and we research the diversion characteristics of the soil-root interstice in soil of the slope with developed vegetation and its contribution to the rainfall infiltration by the method of the field and indoor test, statistical analysis and mathematical model and so on, we also analysis the change of the shallow slope stability of vegetation Inhibition which caused by the gap of the soil-root. As a result, we get the following main achievements from the research:(1) The regularity of the root density is reduced with the increase of soil depth in the soil is widespread, and which spatial distribution is affected by many factors such as vegetation types, geological conditions, the growth time, climate conditions and so on. The root-soil gap is a universal phenomenon of plant roots stretch, and its diversion phenomenon universal existence and it is widespread in the slope of the soil without the limitation of area, vegetation types, climatic conditions and geological conditions; and the diversion characteristic of the root-soil gap is weakening with the root decaying as the increase of soil depth.(2) The physical characteristic of soil has great difference between Chenggong and Touzhai, and the seasonal changes have little effect on it. In Touzhai the porosity of unsaturated zone soil, moisture content, organic matter content and the degree of root biomass are higher than that in Duanjiayin, the physical properties of soil in Touzhai has high porosity, low bulk density and high moisture content, and which has a relationship with the high organic content. At the same soil depth, the infiltration rate of soil in Touzhai is always higher than it in Duanjiayin, and the saturated infiltration rate of soil and the initial infiltration rate of soil always have great difference in Touzhai. However, both the saturated infiltration rate of soil and the initial infiltration rate of soil have little fluctuation in Duanjiayin.(3) The influence of the size of the soil-root interstice for the resistance characteristics of water infiltration are related with Re, the influence of the interstice size for the frictional coefficient shows positive correlation to Re. Compared the traditional empirical formula with the model one, it is more closer to the actual situation to use the resistance model of improved KAYS to study the resistance properties of the soil-root interstice, and which has a certain practicality; In addition, we have gotten that the velocity distribution of water infiltration in different soil-root interstice through the second integral which is based on Navier-Stokes equations; the result is based on the process of dynamic measurement, from a certain extent, has reflected the relationship between the moisture of soil and soil-root interstice.(4) In the process of rainfall, the soil-root interstice has a well diversion features in the slope with developing vegetation, and the diversion volume rate of soil-root interstice in Duanjiayin is 72%-82% of total infiltration, and which is 54%-70 in Touzhai. It has weakened the generation of surface runoff as the soil-root interstice promote the water infiltration in soil.