Undrained Triaxial Compression Tests on Artificial CO2-hydrate-bearing Sand Specimens

Abstract

Global warming has been recognized as one of the severe issues of global scale which should be addressed immediately. CO2 capture and storage technologies have been believed to be an expected countermeasure for reduction of the greenhouse gas released by plants and industrial activities. Recently, a new method for CO2 capture and storage has been proposed by some researchers, that is, CO2 sequestration in the form of CO2-hydrate under the seafloor. In this method, CO2 is injected into the sandy layer of seabed ground where the CO2-hydrate can exist stably. In order to achieve the safe and sustainable sequestration, it is essential to characterize the mechanical response such as stress-strain relationships or deformations of CO2-hydrate-bearing sandy sediments. In the present study, we have conducted a series of undrained triaxial compression tests on artificial CO2-hydrate-bearing sand specimens. From the experiment results, it is found that both stiffness and shear strength of CO2-hydrate-bearing sediments increase as increases in content of CO2-hydrates, and excess pore water pressure is reduced so that negative excess pore water pressure can be observed. The CO2-hydrates in the pore spaces seem to play a role of supporting the soil skeleton and it acts as additional sand particles which enhances the dilation behaviour of the sandy sediments.