ADVANCES OF RESEARCH ON MECHANICAL PROPERTIES OF GAS HYDRATE DEPOSITS

Gas hydrates (GH) aredefined as the crystalline solid, or clathrate hydrates, which areformed by some types of low mass molecular gases, such as methane,carbon dioxide, and hydronitrogen et al, with water underrelatively high pressure and low temperature conditions. Gashydrate deposits (GHD) are some sand, clay and mixture soilsediments which contains gas hydrates. Advances of the research onthe mechanical properties of the gas hydrate deposit aresummarized in the aspects of in-situ investigation, laboratorytest and theoretical model. Firstly, the in-situ investigations,including the in-situ tests (such as downhole test) and thephysical properties tests on board, are summarized and theapplication of pizo-cone penetration test in the GHD geotechnicalinvestigation and the study of mechanical properties of GHD arediscussed. Secondly, some recent research advances in thelaboratory test are presented, including mainly the tri-axialcompression tests on the natural and synthesized GHD samples, theacoustic tests for measuring the elastic coefficients and thetests for studying the effects of the main factors such as the gasand water contents and the soil type on the strength of GHD. Somelaboratory tests are also summarized regarding the hydratedissociation influences on the strength of hydrate deposit duringgas hydrate exploitation. Thirdly, several theoretical models forestimating the mechanical properties of GHD are introduced, andtheir main characteristics and application ranges are discussed.Based on the above summary, emphases and tendency in the futureresearch on mechanical properties of GHD are finally discussed.