关键词: 水合物粉混合法, 非饱和法, 直剪试验, 强度

Abstract: To better explore the effect of different hydrate habits on the mechanical properties of hydrate-bearing soils, a combined injection synthesis and direct shear testing system has been developed. The system includes a hydrate injection synthesis setup and a hydrate-bearing soil direct shear apparatus under low temperature and high pressure conditions. The sprayed water mists can widely contact with hydrate-forming gas using the spraying water equipment, and thus gas hydrate can be synthesized quickly and efficiently under the high-pressure and low-temperature environment in the container. The system can be used to prepare hydrate-bearing samples by combining the unsaturated method and the hydrate powder mixing method. Different sample preparation methods correspond to different hydrate habits. Hence, the new direct shear tests can compare the shear strength of hydrate-bearing soil under different hydrate habits. Using silty sand and carbon dioxide hydrate as the tested materials, the direct shear tests of cemented and pore-filling hydrates were carried out. The results show that the shear strength of hydrate-bearing soil is higher for the cementation habit than for the pore-filling habit, which verifies the reliability of the instrument.

Key words: hydrate powder mixing method, unsaturated method, direct shear test, strength