Effects of Sample Size on the Stress-Permeability Relationship for Natural Fractures

Abstract

This report is one of a series documenting the results of the Swedish-American cooperative research program in which the cooperating scientists explore the geological, geophysical, hydrological, geochemical, and structural effects anticipated from the use of a large crystalline rock mass as a geologic repository for nuclear waste.

Effect of highly pervious geological features on ground-water flow into a tunnel

“…The correlation between joint closure and joint effective normal stress is generally characterized as nonlinear and hysteretic as observed by many researchers (Snow, 1972;Goodman, 1974;Iwai, 1976;Gale and Raven, 1980;Barton and Bandis, 1982;Bandis et al, 1983 (Heuer, 2005). topography, joint surface roughness, mechanical properties of asperities, and the nature of infilling materials.…”

Effect of size on fluid movement in rock fractures

“…In another more recent investigation u'sing samples ranging in size from 10 to 30 cm, the opposite effect was found (Gale and Raven, 1981). Since both studies assumed the validity of the cubic law as expressed in equation 1, it is conceivable that the seemingly contradictory conclusions are simply a manifestation of the effects of fracture surface roughness, which could very well show up in the different size samples in a completely unsystematic fashion.…”

“…However, other inve stigations on natural fractures, where the effects of weathering were present (Gale and Raven, 1981) or on fresh rock fractures that were arbitrarily roughened in varying amounts (Kranz, et a1. 1979) have produced mixed results.…”

Evaluation of models for estimating changes in fracture permeability due to thermo-mechanical stresses in host rock surrounding a potential repository

“…Qualitative arguments about the experiment are used to explain how quantities, such as aperture, are determined and to explain differences between prediction and simulation. Aperture estimations are further complicated because the applicability of the cubic law for flow in a fracture deteriorates as the normal stress and fracture roughness increase (Gale and Raven, 1980). Shortcomings of the joint models in UDEC during cyclic and reverse shearing are mentioned here; they are discussed in more detail in a Nuclear Regulatory Commission-sponsored study (Hsiung et al, 1994).…”