In order to study the hydraulic characteristics of unsaturated flow in single fracture, a method for generating the distribution of fracture aperture using Weierstrass-Mandelbrot function was proposed according to fractal dimension,dislocation value and contact area of fracture surface.Based on the assumption that a parallel-plate approximation can stand in the subregion of the fracture,a numerical model for simulating unsaturated flow in single fracture considering the quasi-static water exchange between fracture and matrix was built up.The simulated relationships between capillary pressure and saturation and between unsaturated hydraulic conductivity and capillary pressure of fracture could be used to describe the hysteresis during drainage and imbibition and figure out the air-entry value and the residual water saturation during drainage.The qualitative comparison of simulated results and experimental results showed that the proposed model is feasible and reliable in modeling the unsaturated flow in single fracture considering the water exchange between fracture and matrix.Finally,comparisons of relation curve between unsaturated hydraulic conductivity and capillary pressure by taking water exchange into account or not was conducted.The result showed that the fracture-matrix exchange is negligible under high capillary pressure (low saturation).
