Triaxial Compressive Property of Unconsolidated Sand Containing Supercritical CO_2

摘要

It is essential to consider the geomechanical behavior of a CO_2 reservoir to ensure sustainable CO_2rngeological storage. The mechanical properties of soil containing CO_2 are essential to simulate therngeomechanical response to CO_2 geological storage in sub-seabed formations. Although some worksrnconcerning laboratory tests for geomechanical characterization of a CO_2-containing rock or coal havernbeen reported, no triaxial compression test method for a CO_2-containing soil sample has beenrndeveloped, and thus the triaxial compressive property of such samples has not been clarified. In thisrnstudy, a method of preparing an artificial sandy soil specimen containing supercritical CO_2 and arndrained triaxial compression test method for those specimens were developed. Axial loading wasrnconducted at an axial strain rate of 0.1 %/min under a drained condition, while maintaining porernpressure at 9 MPa, cell pressure at 18 MPa and temperature at 313 K. These conditions of temperaturernand pressure were determined with reference to the environment of an expected field of sub-seabedrnformations around Japan. Specimens consisting of sand, water and supercritical CO_2 were preparedrnand the triaxial compressive properties of them were successfully obtained. The stress-strain curve ofrna CO_2-containing specimen was found to be quantitatively similar to that of a water-saturatedrnspecimen, although deviator stress for CO_2-containing specimen seems to be slightly larger than thatrnfor water-saturated specimen at axial strain of more than 0.1 probably owing to the effect of suction inrnthe CO_2-containing specimen. From a viewpoint of geotechnical engineering, CO_2-containing soil canrnbe merely considered as unsaturated soil.