The permeability of Pocheon granite was measured for samples cracked thermally at temperature ranging 200 to 600øC as a function of pressure to 40 MPa. Samples with induced tension fractures were also measured at pressure up to 55 MPa. The permeability of the whole rock ranged from 7.2 x 10 -7 to 2.4 x 10 '7 darcies. The permeability of the thermally cracked rocks ranged from 1.8 x 10 -? to 5.4 x 10-7darcies, depending on the maximum thermal cycle temperature. Pressure had greater effects on samples treated to the lower thermal cycle temperature than on the higher thermally treated ones. The increase of permeability was most pronounced between 500 and 600 øC. It was showed that the power n in the relationship relating permeability k to effective porosity ? by k oc ?" failed in the range 2.6?<3.0. The permeability of jointed rocks ranged from 1.2 x 10 -? to 3.6 x 10 -6 darcies, which was dependent on the roughness ofjoint surface. As JRC increased, the permeability decreased exponentially. Large permeability hysteresis resulted when the pressure was cycled.
The knowledge of transport property of rocks on which joint and temperature have a large effects is required to understand various problems of geotechnical interest, particularly those involving high-level radioactive waste storage in underground chamber and geothermal energy recovery.
In many impermeable rocks, the flow of fluids occurs nearly exclusively through joints and they control the permeability of crystalline rocks. Many investigators have performed studies of the influence of joint parameters on the transport property of jointed rocks. (Gangi 1978, Kranz et al. 1979, Trimmer et al. 1980, Walsh 1981, Ryan & Farmer 1987, Brown 1989). The permeability of joint depends principally on joint aperture and roughness, and decreases under increasing the confining pressure because the aperture decreases and the fluid path is more tortuous. In this contribution, an attention will be focused on the effects of surface roughness of joints on the permeability of jointed rocks.
Temperature is another important factor of perturbing the transport property of rocks. If a rock is heated, new cracks may form in or between the mineral grains and preexisting cracks can either close, open or extend (Friedman & Johnson 1978, Johnson et al. 1978, Hornand-Etienne & Troalen 1984, Hornand-Etienne & Poupert 1989). Such thermally induced cracks can increase the porosity of rocks and influence substantially the transport property of rocks. (Summers et al 1978, Heard 1980, Heard & Page 1982, G?raud 1994). Bauer & Johnson (1979) shows that thermal crack formation in the Westerly granite occurs almost entirely at temperature below the or to 15 transition of quartz (T?0) and the greatest rate of permeability increase occurs near T?0.
The purpose of this study is to investigate the influence of the joint surface roughness and thermal cycle temperature on the permeability of Pocheon granite.