Recent Works
Jiro Yamatomi, Gento Mogi and Tsuyoshi Adachi
University of Tokyo
Modeling and analysis of fluid flows through a rock fracture with wall roughness
Fluid flows through a rock fracture are commonly described by the cubic law or parallel plate model. However, deviations from this model are evident, because rock fracture surfaces are rough and con-tact each other at discrete points. The roughness of the fracture walls as well as the increasing con-tact area and flow path tortuosity at high normal stress must cause deviations from a parallel plate model in which the rate of flow through smooth walls is assumed to change with the cube of its opening.
In order to clarify the effects of wall roughness and partial contacts of natural rock fractures, we made rock fractures with wall roughness numerically produced by the fractal theory and conducted numerical simulations. We also carried out hydromechanical FEM analyses of rock slopes with a single and inclined rock fracture and studied water pressure distribution in the rock fracture.
By the numerical simulation of fluid flow through a single fracture with wall roughness, it was found that deviations from the cubic law occurred when the surface contact area ratio increased to around 0.1. The decrease of flow rate with closure of the fracture is found much larger than that of the cubic flow rule (Figure 3). We also examined the difference in water pressure distribution between single inclined fractures running through a rock slope with and without wall roughness, and found that the peak values of the water pressure in the case of rough wall surfaces are on average smaller than those generated in the fracture with smooth wall surfaces.
Also, you can find the details of the study in
(a) Jiro Yamatomi, et al.，Modeling and analysis of fluid flows through a rock fracture with wall roughness， (Proc. of the 38th US Rock Mechanics Symposium, (Washington DC), Submitted, 2001).
(b) J. Yamatomi, et al., Hydromechanical analysis of rock slopes (Proc. 96 Int. Symp. On Mining Science and Technology (Xuzhou), (353-358), 1996).