Experimental characterization of the hydraulic and mechanical behavior of a jointed rock specimen
A laboratory experiment to study the permeability of fractured granitic rock under stress is presented. The test specimen measured one meter diameter by two meters length and contained numerous joints of varying size and strength. Four of the joints extended through the sample and intersected to form a network of flow channels. Uniaxial compression was applied to the specimen and radial flow through the fracture network was measured at several different stress levels. Changes in fracture apertures were monitored independently from the overall specimen deformation. Using a 3-D numerical model based on parallel-plate conduits, the relationship between aperture and flow through individual fractures was investigated. One fracture oriented perpendicular to the loading axis was responsible for most of the flow. Its minimum hydraulic conductivity of about 2 cm/sec at 7.48 MPa normal stress was substantially greater than that reported in previous large scale tests. The rate at which conductivity decreased with increasing stress, however, was of comparable magnitude. The specimen failed through a combination of fracturing through intact rock and healed joints and shearing along pre-existing open joints. The ultimate uniaxial stress of 7.55 MPa was about one-tenth the compressive strength of small core samples with similar joints, whereas other scale effect studies have reported factors of one-half to one third. 64 refs., 79 figs., 16 tabs.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 7079523
- Report Number(s):
- UCRL-53763; ON: DE87005925
- Resource Relation:
- Other Information: Thesis. Portions of this document are illegible in microfiche products. Original copy available until stock is exhausted
- Country of Publication:
- United States
- Language:
- English
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