Study of mechanism and theoretical model of seabed destruction caused by gas hydrate dissociation

Abstract

Gas hydrate decomposition is an important cause of submarine geological hazards. Understanding the mechanism of overlying seabed failure caused by gas hydrate decomposition is important to engineering practice and geological hazard prediction. In this paper, an observational device is designed to simulate the process of seabed failure caused by gas hydrate decomposition and the evolutionary process of seabed failure under different seabed thickness and slope conditions is compared and analysed. The mechanism of seabed damage is also discussed. In addition, based on the seabed failure mechanism, a computational model for the influence of hydrate dissociation on seabed stability is established. It is found that in shallow or steeper strata, the seabed will be destroyed by shear slip; however, when the stratum is thicker or the slope is gentle, the seabed surface first collapses, then is deformed and destroyed. The excess pore pressure ratio of the seabed in critical failure state is only related to the seabed gradient. The larger the gradient, the smaller the critical excess pore pressure ratio.

Keywords:

• Gas hydrate decomposition
• excess pore pressure ratio
• excess pore pressure
• slope stability
• failure mechanism

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was jointly supported by the National Natural Science Foundation of China (No. 41672272; No. 41427803; No. 41806075), the National Key Research and Development Program of China (No. 2017YFC0307701), Fundamental Research Funds for the Central Universities of Ocean University of China (No. 201962011), Primary Research and Development Plan of Shandong Province (No. 2017GGX30125), Marine Geological Process and Environmental Function Laboratory Open Fund (No. MGQNLM-KF201709; No. MGQNLM-KF201804), and The Fundamental Research Funds of Shandong University.