Abstract

The outburst fragmentation of soil caused by the dissociation of the gas hydrate was studied based on experiments and numerical simulation. The dense discrete particle model (DDPM) combined with the kinetic theory of granular flow (KTGF) was presented to reveal the outburst morphology of soil, considering the interphase forces and frictional effect between soil particles. The numerical simulation results in geometric features are consistent with the high-speed photography results. Moreover, the effects of initial gas pressure and thicknesses of the overlying layer on the occurrence of gas outburst were investigated in the experiments.

Introduction

Gas hydrate (GH) has become an important strategic energy source in China due to its large reserve and small pollution. Many countries in the world have accelerated the exploration and development of GH. However, concerns are increasing on the possible geological disasters, even hazard chains caused by exploitation activities. The dissociation of GH from hydrate-bearing sediments during the exploration can cause the softening of soils and the formation of excess pore gas pressure (Zhang et al., 2015). The hydrate sediments become a gas-liquid-solid phase slurry structure after the hydrate dissociation. The rheological of hydrate sediments slurry is a typical multiphase nature depended on the sediments concentration, temperature and shear rate. Nair et al. (2019a, 2019b) studied the rheological behavior through the different contrast experiments to explain the causes of the rheological behavior of hydrate slurries in marine sediments. When the accumulated pressure after the hydrate dissociation equals or exceeds the soil's resistance because of gravity and shear strength of the overlying layer, the plastic failure or gas outburst which the high-pressure gas drives the overlying soil to form multiphase flow could occur. The hydrate dissociation process is not considered because of the complexity of hydrate sediments. The paper focuses on the multiphase flow after the plastic failure of the overlying layer.

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