水合物分解条件下海底边坡失稳演化机理及流固耦合分析方法

水合物开采或自然分解，极易诱发大陆坡海底边坡失稳甚至引发大规模海底滑坡，严重威胁开采井及水下基础设施安全。针对水合物富集和滑坡地质灾害频发的南海北部深水大陆坡，概化典型双层土边坡工程地质模型，建立融合VOF技术的三相耦合计算力学模型；改进离散元剪切模量衰减模式并引入边坡稳定系数矢量和法，发展水合物分解气体作用下海底边坡失稳演化过程及稳定性动态评价的CFD-DEM流固耦合数值方法，并开发基于先进量测技术的水下边坡大型鼓式离心机试验进行验证；系统模拟海底复杂地形、土性分布、沉积形貌和水合物条件等控制因素下海底边坡的实时稳定性及大变形失稳演化过程，揭示海底浅层滑坡的流固耦合诱发机理和失稳模式及灾变演化规律；通过变动参数研究，建立主控因素与边坡状态变量及稳定系数的内在关系，提出海底滑坡预测判据。该成果可为水合物区及开采工况下海底边坡动态稳定性评价、滑坡预测预警及海洋工程防灾减灾提供重要科学支撑。

The exploitation or natural dissociation of gas hydrate will induce the instability of submarine slopes on the continental slope and even large-scale submarine landslides, which seriously threatens the safety of exploitation wells and undersea infrastructures. Aiming at hydrate-enriched and frequent geo-disaster northern slope of the South China Sea, based on a typical two-layer soil slope, the engineering geological model is generalized, and a three-phase coupled numerical model is introduced based on the VOF method. In addition, by improving the discrete element shear modulus reduction model and introducing the safety factors vector-sum method, the CFD-DEM fluid-solid coupling numerical method is developed for the instability evolution process and dynamic stability evaluation of submarine slopes under the condition of hydrate gas. Moreover, the large drum-centrifugal model test of underwater slopes based on the advanced monitoring technology is used to verify the numerical method. Furthermore, the real-time stability and evolution of large deformation instability of submarine slope under the main control factors such as complex terrain, soil layer characteristics, sedimentary morphology and hydrate dissociation condition is systematically simulated to reveal fluid-solid coupling induced mechanism, instability pattern and catastrophe evolution law of submarine shallow landslide. Based on comprehensive study of changing parameters, the quantitative relationship between main control factors and slope state variables as well as stability factors is established; the prediction criterion of the submarine landslide is proposed. The results can provide a scientific basis for the dynamic evaluation of submarine slope stability, the prediction and warning of landslides and the disaster prevention and reduction of ocean engineering in the hydrate-enriched area and exploitation condition.