Unsaturated Hydrualic Properties Ofa Single Crack Based On Random Field Theoryand Its Effects On Slope Stability

Landslide is one of the most devastating natural disasters; it gives one of mankind tremendous loss of life and property. Rainfall is one of the main factors induced landslides. For cohesive soil, rainfall is not easy to seepage to, because of the low permeability coefficient. But because of dry wet circulation effect or deformation of soil, the cracks will be produced; these cracks make rain easy to infilt into soils, which eventually led to the stability of the slope reduced. The researchers, though, have come to realize that when evaluate the stable of slope, the crack must be considered, but it is still lack of systematic theory to describe the role of crack, the methods on the stability with crack were too simplified, for example, gives crack or crack soil larger permeability coefficient; Think crack filled with water, crack is treated as head boundary conditions, etc.Actually fracture permeability coefficient is not constant, the initial condition of crack is not saturated, in the rainfall process, the crack exist saturated-unsaturated process. This part has some research, but basically no application to soil seepage analysis and evaluation of the slope stability of soil slope. The hydraulic characteristics of crack are directly related to the form of the crack. the aperture of crack and distribution of the crack determine the permeability of crack.. the soil water characteristic curve also have relationship with the aperture and its distributionIn conclusion, the purpose of this study is to study the spatial distribution of the crack, then study the hydraulic characteristics of crack, and then we study the stability of soil slopes with crack.The main focus of this study includes three aspects: firstly, the crack aperture with random field parameters. Secondly, establish the soil water characteristic curve of crack and permeability function in the numerical model. Thirdly, based on the soil water characteristic curve and permeability function of the crack, using numerical simulation method, analysis stability of crack soil slope under rainfall condition. And study the depth and crack position, rainfall intensity on the influence of slope stability.The main result of this study also includes three aspects: firstly, extract the edge of crack from the image applying the live-wire method, and set up the random field theory model of crack, and verify the probability distribution of crack aperture, found that the probability distribution of the crack follew the log-normal distribution and normal distribution. Then calculate the parameters of random field theory : the application of exponential function fitting the autocorrelation function of the crack and application correlation function method calculating the scale of fluctuation, the study found that when sampling space less than 1/10 of The scale of fluctuation, the results of the scale of fluctuation are reliable. Secondly, based on the theory with the random field method the soil water characteristic curves can be obtained, and application of numerical method, consider trap effect, get the soil water characteristic curve, the results show that the results is better considering traps effect. This can reflect soil water characteristics curve have larger residual water content. Third, consider the hydraulic characteristics of crack, the influence of seepage and stability, the results show that the crack of the deep, longer rain time, higher initial pore water pressure, the more likely the rain infiltration in soils from crack , at the same time, reduce the stability of the slope.