Gas hydrates are crystalline solids comprised of a lattice of water molecules that encapsulate natural gas molecules. Hydrates form under specific conditions of high pressure and low temperature when the supply of gas is sufficient to initiate and stabilize the hydrate structure. It is important to further our understanding of the geotechnical behaviours of hydrate-bearing soils during hydrate dissociation because of their potential to initiate and propagate submarine slope failure and be recovered as an energy resource. This thesis focuses on the pore pressure response and volume change of sands during isotropic undrained hydrate dissociation.;Physical effects, such as stress and deformation changes of carbon-dioxide hydrate dissociation on the surrounding sand are presented based on the results of this research. The triaxial test data indicate: (1) dissociation of even a small percentage of gas hydrate caused a dramatic reduction in the effective stress and lead to soil failure; (2) the specimen expanded even during isotropic undrained dissociation; (3) the higher the pressure, the higher hydrate content; (4) the lower the temperature, the higher hydrate content; (5) the greater the amount of gas hydrate initially present in the specimen, the greater the reduction of effective stress upon gas hydrate dissociation. Comparison of laboratory results with the predicted response showed a correspondence.;Three groups of carbon-dioxide hydrate-bearing sand specimens were formed using a specialized triaxial test apparatus. The first group of tests included carbon-dioxide hydrate-bearing sand specimens formed under a cell pressure of 2.6 MPa at a temperature of 1° C, 2.3° C, 4° C. The cell pressure was increased to 2.8 MPa and 3 MPa for the second and third test group, respectively. Sample temperatures were raised to 26° C for complete dissociation of the carbon-dioxide hydrate.
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