| Fractures in granite rock mass always provide the major channels for nuclide to escape to the biosphere. When planed to dispose HLW (high level radioactive waste) into these kinds of hard rock mass, joints are one of the most important factors to be considered carefully. This paper based on the site investigation of Beishan Area, Gansu province, the preselected area of Chinese High Level Radioactive Waste. In-situ investigation, borehole water inflow test, statistics analysis, lab test and numerical simulation are done to better understand the distribution trends, joint surface characteristics, joint mechanics and the coupled water flow in rock mass.More than 500 outcrops are investigated in one of the preselected area-the quarry area, geological and statistical methods are used to study about 12000 joints scattered in these outcrops. Some basic characteristics such as dip, dip direction, space, aperture, mean trace length etc are obtained and these joints are subdivided into 4 groups. This work is the foundation of further study of fracture's another property.It is well known that nature fracture is always undulated and rough, the characteristics of fracture surface is one of the most important factors to affect its action. It is necessary to research about these characteristics especially in-situ joint. A geometry approach based on Barton'straight edge method is introduced to these investigation, plenty of large scale surface configuration profile curves are obtained. It shows that scale effect, anisotropy are prominent for these profile curves, and JRC (joint roughness coefficient) of tensile fracture is always 1.24 times larger than that of shear joint.Undulate part and rough part are two basic components of the nature fracture. Undulate part is always characterised with large undulate breadth and long undulate cycle, and rough part is defined on the contrary way. These different properties lead to absolutely different effects on joint's mechanics and hydro-mechanics. It is an interesting work to separate these different parts from the original profile curve. Frequency analysis is used to make it done. In this method profile curve can be seemed as a discrete time series and different parameters of different parts are obtained. Another important aspect is the determination of the valve separate frequency which is also discussed in this paper.Lab test is the most direct and effective ways to study joint's properties. But how to get these test samples with nature joints is not an easy work. Under the help of special rock product machines some rock samples with standard scale of 150×150×150mm are obtained and well-conserved for lab test. Normal compress test and direct shear test are performed on these samples, and before these tests the profile curves of the fracture located in the mid of sample are analysed. Rules of effect of surface configuration on fracture'mechanics properties are obtained through these tests. Hydraulic method is used to measure geo-stress, and high water pressure inflow test is carried out in a 500m deep borehole. UDEC is used to analyse the couple effect of H-M on a fracture net, and this net is created based on the former investigation. |
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