Submarine slope failure due to overpressure fluid associated with gas hydrate dissociation

Abstract

The dissociation of gas hydrates can increase pore pressures greatly, thereby causing the shallow layers of submarine slopes to fail. Given the high failure risk of shallow subsea soils, it is important to understand the stratum response mechanisms after hydrate dissociation. In this paper, submarine slope failure triggered by overpressure fluid associated with gas hydrate dissociation is investigated in laboratory experiments. A two-layer geological model is built based on actual geological data, and pressurised air is injected into the model to simulate the overpressure fluid. The pore pressures, surface displacements and internal deformations of soils are measured and compared under different conditions, and their evolution processes are analysed for various parameter values. The results show that the accumulation of pore pressure increases with the thickness of the soil layer and leads to layered fractures. The failure pattern can be generalised into two types: (a) disc-shaped failure and (b) penetration failure. In disc-shaped failure, a major failure occurs when the shear stress reaches the shear strength, whereas tensile fracturing is a major effect in penetration failure. This achievement is very important for a deep understanding of submarine landslides induced by overpressure fluid, as well as for risk assessments of ocean engineering sites.

Deep seabed mining: Frontiers in engineering geology and environment

“…A wooden drilling platform with a large size and shallow operating level was first employed. Steel offshore platforms began to be used in the 1950s and 1960s, resulting in the rapid development of offshore oil and gas resources (Nian et al 2022). By the late 1960s, the operating water depth had exceeded 200 m. In 1973, the first concrete platform was built in the Ekofisk oilfield in the North Sea (Aitcin and Houle 1986).…”

“…The evaluation report should describe the characteristics of the regional engineering geology environment as well as identify and evaluate geologic disasters and the corresponding mitigation measures (Aurelio 2004). On-site investigations should cover the regional structure, topography, landform, stratigraphic composition, physical and mechanical properties of sediments, hydrodynamic environment, site stability, and geologic hazards (Campbell 1997;Price 2008;Griffiths 2019;Nian et al 2019;Guo et al 2020a;Fan et al 2020b;Shen and Shen 2022;Nian et al 2022). Based on the above, and with reference to the mature evaluation process for onshore engineering geology environments, which has been implemented for decades, this study identifies a method to evaluate the engineering geology environments of deep seabed mining sites.…”

Geomechanical Properties of Deep-Sea Pore-Filled Methane Hydrate-Bearing Soils at Critical State Using DEM Analysis

“…Therefore, there is a growing focus on surveying the physical, thermodynamic, chemical, and mechanical properties of MHBS, as well as developing technological methods for identifying and exploiting MHBS deposits ( [6,7]). However, it is important to consider the potential hazards associated with safe mining, such as submarine landslides and tsunamis ( [8][9][10][11][12][13][14][15]). Therefore, the geomechanical properties of MHBS are crucial to understanding from the view of geotechnique ( [16][17][18][19]).…”

Effect of Low Temperature on the Undrained Shear Strength of Deep-Sea Clay by Mini-Ball Penetration Tests

“…Marine engineering construction has moved to the deep sea, and researchers are paying more attention to the undrained shear strength of deep-sea clay [1], which is crucial for the design and installation of marine pipelines [2,3], development of marine mineral resources [4] and evaluation of marine geological hazards [5][6][7][8][9][10][11]. Nevertheless, the in situ technology for testing the undrained shear strength of deep-sea clay is not well developed, especially for seawater depths exceeding 4000 m [12].…”