並列タイトル等三軸圧縮下における岩石の浸透率に対する温度と封圧の影響
一般注記To clarify the permeability behavior of rock during deformation and failure, and the influences of confiningpressure and temperature on that behavior, triaxial compression tests were carried out for Shikotsu weldedtuff, Kimachi sandstone, and Inada granite under confining pressures of 1–15 MPa at 295 K and 353 K.Main findings are (1) Effects of confining pressure: For Shikotsu welded tuff, the permeabilitymonotonously decreased with axial compression. The decrease ratio increased with confining pressure; themain cause of the decrease was attributed to pore collapse. For Kimachi sandstone, the permeability firstdecreased with increasing axial stress, but then began to increase when the total lateral strain recovered itsvalue before the application of confining pressure, and finally showed an almost constant value in thepost-peak region. The minimum and final permeability decreased with confining pressure. Compared to thepermeability before axial compression, the final permeability became larger under small confining pressurebut smaller under high confining pressure. The main cause of the decrease was attributed to eithercompaction or large plastic deformation of clay cementing materials. For Inada granite, the permeabilitybehavior during axial compression was almost the same as that for the Kimachi sandstone. Compared to thepermeability before compression, the final permeability was larger, and it decreased with smaller confiningpressures. The main causes of the decrease were attributed to a decrease in the number and width of ruptureplanes and a decrease in the axial cracks from biotite; however, the permeability increased under largerconfining pressures because of the formation of subrupture planes due to high stress concentration at therough and stiff rupture plane. (2) Effect of temperature-confining pressure coupling: For all types of rock,the permeability at 353 K was lower than at 295 K, and the influence of the confining pressure was less at353 K than at 295 K. The principal mechanisms causing the permeability decrease were enhancement ofiiipore collapse for the Shikotsu welded tuff, plastic deformation of the cementing material for Kimachisandstone, and viscous deformation of mineral particles for Inada granite by thermal activation. The flowvelocity of the fractured specimens with the unit pore pressure gradient at 353 K was slightly lower underlow and moderate confining pressures but almost same under high confining pressures for the Shikotsuwelded tuff, slightly higher for the Kimachi sandstone, and obviously less for Inada granite compared tovalues at 295 K. The change in sealabilty of underground openings due to the progress of EdZs and EDZswere also inferred by considering the rupture plane in the triaxial compression tests analogous to a fracturein a rock mass.
(主査) 教授 藤井 義明, 准教授 児玉 淳一, 教授 川﨑 了, 特任教授 田中 洋行
工学院（環境循環システム専攻）
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