Study On Permeability Properties Of Single Fractures Saturated-Unsaturated Seepage In Rock And Its Engineering Applications

Because the permeability of fractures is much larger than that of matrix in rock mass,the main seepage channels of rock mass are composed of fractures.Therefore,the penetration capacity of fractured rock mass is mainly determined by the permeability characteristics of fracture.As the basic unit of fracture seepage research,the saturated and unsaturated permeability of single fractures depend on the geometrical characteristics of fractures.In the process of saturated seepage analysis of single fractures,the empirical formula is established by correcting the hydraulic aperture,and in the past,most literatures only considered one of many factors,such as contact area,aperture distribution and roughness,so it is difficult to accurately calculate the saturated seepage of single fractures.For the study of the unsaturated permeability properties of single fractures,there are few relevant experiments and theoretical studies,and more of the theory of porous media is used to establish the corresponding theoretical model and empirical formula.In fact,the microscopic structure and seepage path of fractures in rock mass are fundamentally different from those of porous media.In view of the above problems,this paper is studied mainly through the following three aspects:(1)With aperture distribution,roughness and contact area considered,the empirical formula for calculating saturated seepage in single fractures is put forward.Based on the development environment of C + +,the numerical analysis method of saturated seepage in single fractures is given,and the influence mechanism of hydraulic gradient,aperture distribution and fractal dimension on permeability is analyzed,then the model for saturated seepage in single fractures considering aperture distribution,roughness and contact area is established;And compared with the prediction results of Zimmerman's,Yeo's and Wang's correction formula,the validity of the proposed model in the calculation of single fractures seepage is verified.(2)For unsaturated seepage in single fractures,combined with aperture probability density function,the relationship of relative permeability-saturation function is established,namely van Genuchten-Mualem model.Compared with the test data of unsaturated seepage in rough fractures with different aperture distribution,the reliability of the theoretical model is verified.Based on Invasion percolation model,Cubic theorem and fractal geometry method,a numerical simulation method of relative permeabilityt-saturation relation is established.Comparing the results of numerical simulation about relative permeability-saturation of fractures and the theoretical results of the VG-M model under different fractal dimensions,the applicability of the theoretical model to describe the relation between the relative permeability and saturation of different rough fractures is further verified.(3)Based on the above modified hydraulic aperture formula and relative permeability-saturation model,the permeability function and volume water content function of each rock material are obtained,and the safety factor of fractured rock slope under rainfall condition is calculated by using Geostudio numerical software about SEEP/W and SLOPE/W program.The influence mechanism of rainfall infiltration on the stability of fractured rock slope is revealed.