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Understanding triggering mechanisms of submarine landslides is of great importance in view of the high risk they cause to human beings and facilities in the sea. Submarine landslides triggered by elevated pore pressures associated with gas hydrate dissociation were studied by centrifuge modeling and analysis of submarine slopes in saline water. Pressurized water was introduced into the sand to simulate the increased pore pressures caused by gas hydrate dissociation. The test results and analysis highlighted two mechanisms: (1) Accumulation of high pore pressure and associated tensile failure. Gentle slopes and thick clay favored the accumulation of pore pressure. Release of accumulated high pore pressure resulted in major pockmarks caused by tensile failure. Pore pressures at failure were up to 2.2 times the vertical effective stress of soil. The failed mass was intact and showed low mobility. (2) Fracturing in clay and associated shear failure. Fractures readily formed in steep slopes or thin clay during its downward movement, enabling the dissipation of pore pressure. The accumulated pore pressures at failure were close to or less than the vertical effective stress of soil. The failed mass was liquefied and attained high velocity due to mixing with water. [ABSTRACT FROM AUTHOR]

Abstract: Modified graphite oxide (MGO)/Poly (propylene carbonate) (PPC) composites with excellent thermal and mechanical properties have been prepared via a facile solution intercalation method. An intercalated structure of MGO/PPC composites was confirmed by X-ray diffraction and scanning electron microscope. The thermal and mechanical properties of MGO/PPC composites were investigated by thermal gravimetric analysis, differential scanning calorimetric, dynamic mechanical analysis, and electronic tensile tester. Due to the nanometer-sized dispersion of layered graphite in PPC matrix and the strong interfacial interaction between MGO and PPC, the prepared MGO/PPC composites exhibit improved thermal and mechanical properties in comparison with pure PPC. Compared with pure PPC, the MGO/PPC composites show the highest thermal stability and the T g is 13.8 °C higher than that of pure PPC, while the tensile strength (29.51 MPa) shows about 2 times higher than that of pure PPC when only 3.0 wt.% MGO is incorporated. These results indicate that this approach is an efficient method to improve the properties of PPC. [Copyright &y& Elsevier]