In this study, for the purpose of evaluated the mechanical and the permeability characteristics of rock fractures having rough surfaces and undergoing shear deformations, the permeability shear tests were performed on the specimens made artificially. The shear test under both the constant normal load condition and the constal1lnormal stiffness condition were adopted. The test results described that the macroscopic permeability characteristics of the whole fracture are greatly affected by the microscopic void structure created by surface roughness, and the permeability characteristics is related to the mechanical characteristics also.
With the recent increasing public concerns over the Underground disposal of high-level radioactive wastes and underground storage of carbon dioxide these days, there is the pressing need for clarifying the groundwater behavior and migration characteristics inside rock. It should be noted that when discussing.
The permeability characteristics of rock, it is of great engineering significance to properly evaluate the permeability characteristics of fractures in rock.
For the purpose of understanding the mechanical and the permeability characteristics of rock fractures having rough surfaces and undergoing shear deformations, the permeability shear tests were performed on homogeneous fracture surfaces without any inclusions, using a specially developed test machine that was able to simultaneously perform permeability and shear tests on rock fractures. The test method proposed here allows the freedom of choice for such parameters as the strength of specimens, roughness in rock fracture surfaces, conditions of fractures loading and hydraulic gradient, as well as the condition of underground rock fractures.
Figure 1 shows the types of shear tests on rock joints. Figure 1a shows the popular shear test under constant normal load condition ("CN L test"), in which normal stress is kept constant during the shearing process (Esaki 1991). As shown in Figure 1b, the mass in question in an unconfined block on a slope slipping on a rock joint surface. The constant volume ("CV test")shear test shown in Figure 1c represents a crack inside the rock under shear, whose deformation is confined as shown in Figure 1d. Figure 1e shows the shear test under constant normal stiffness condition ("CNS test"), CNS test has attracted attention in recent years (Kishida 2002). The fact that real-world rock joints in
(Figure in full paper)
the deep portion of underground display a certain level of stiffness should also be considered. When dealing with the stress condition in rock shown in Figure If, it is easy to imagine that any movement of rock mass (block) leads to the movement of contiguous blocks. Therefore, any movement of a block is assumed to change the stress condition at work. The CNS test IS considered to reproduce more real-world phenomena than other test methods by equating spring stiffness with the stiffness of surrounding grounds.
In this study CNL test and CNS test were adopted as the types of shear test, and the permeability shear test were performed.