Study On The Preferential Flow Pore Spatial Distribution And Water Characteristics Of Collapse Mound Profile In Granite Area In Tongcheng County

Collapse mound is a kind of special soil and water erosion phenomenon occurred in the southern granite red soil region of China, The collapse mound occurred caused Harm is very big, The threat to the ecological environment, people’s life and property safety.In this thesis the research area were located in Wuli and Yanglong, Tongcheng County, Hubei Province where the granite collapse mounds were typical and well-development, the combination of outdoor and indoor experiments and simulation analysis method is used. Through the determination of the collapse mound physicochemical properties, collapse mound of preferential flow pore experiment, porosities of collapse mound layers, soil infiltration capability of collapse mound and dynamic change of water content of collapse mound layers in different periods after raining, the main conclusions are as follows:The different level in collapse mound has significant difference in soil physical properties. In layers of the collapse mound, the bulk density is deposition layer (B-layer)> leaching layer (A-layer)> transitional layer (BC-layer)> parent material layer (C-layer); highest content of clay is B-level, which were higher than30%, minimum content of clay is C-layer, which is less than6%. Clay content of B-layer is7.8times,5.7times,8.4times to C-layer of YanglongI, YanglongⅡ, Wuli Collapse mound. Highest content of the sand is C-level, which were higher than70%, minimum content of the sand is C-layer. The permeability coefficient of C-layer is16.0times,16.1times,12.9times to B-layer of YanglongI, YanglongⅡ, Wuli Collapse mound. Invalid poreThe different level in collapse mound has significant difference in soil porosity. In soil layers of the collapse mound, the highest of aeration porosity is C-layer; the lowest is B-layer. Aeration porosity of C-layer is3.2times,3.3times,3.3times to B-layer of YanglongI, YanglongⅡ, Wuli Collapse mound. The highest of invalid pore is B-layer; the lowest is C-layer. Invalid pore of B-layer is2.3times,2.5times,3.3times to C-layer of YanglongI, YanglongⅡ, Wuli Collapse mound. The higher the aeration porosity, the permeability is better; The higher the inactive porosity, the moisture holding capacity is better.Infiltration performance obvious differences in the surface of collapse mound. Infiltration rate and the collapsed mound wall distance relationship close at different point of the collapse mound. The closer to the collapsed mound wall, the greater the infiltration rate, Such as, the point is apart from the collapsed mound wall0.5m, the soil steady infiltration rate is2.0mm/min; However the point is apart from the collapsed mound wall2.0m, the soil steady infiltration rate is only0.4mm/min. The different level in collapse mound has significant difference in steady infiltration rate, In soil layers of the collapse mound,, the steady infiltration rate is A-layer (1.019mm/min)>C-layer (0.708mm/min)>B-layer (0.198mm/min).Prophase rainfall plays a promoting role in the occurrence of collapse hillock. Accumulation of moisture can reduce the time of filling up the soil,makes the water infiltration into the deeper.After38mm rainfall, collapse mound soil moisture accumulation after the day can reduce0.1d of A-layer full water storage, can reduce0.27d of A and B layers full water storage. It is difficult to infiltration to its duty required the depth to Collapse occurred in a rain. So Accumulation of moisture of prophase rainfall in the soil is an integral.There are preferential flow pore in the soil of collapse mound, With different degree of spatial variation. Exist in70cm range distance to the collapsed wall, the nearer the wall collapsed, the more preferential flow pore. The closer to the collapsed mound wall, the more preferential flow pore, preferential flow pore can make the water enter into the water easily which will lead to so the content of soil water increase, At the same time preferential flow pore is easy to fracture, so it is the most possible collapse part within70cm.Preferential flow pore is existence of local at colluvium heap. It exists in the part close to the collapsed mound wall. It can let more water enter the parent material, and the parent material will be taken away. The physicochemical properties of the parent material layer will be change, Post to pose a threat to the stability of collapse mound. The stability of collapse mound will be threat.