Abstract Free gas in sandy marine sediments is a common occurrence worldwide. A distinct feature of gassy sand is that, under undrained shearing, presence of occluded gas bubbles in the pore fluid can increase the undrained strength of sand at a relatively loose state, while reduce the strength of a relatively dense sand. Previous theoretical analyses have primarily focused on modelling the ‘beneficial’ effect of free gas on loose sand in migrating static liquefaction, with few attempts to describe the ‘detrimental’ effect of gas on dense sand under undrained loading. This study presents a state-dependent critical state model, which describes the distinct behavior of gassy sand with various states in a unified way. Comparison between the model predictions and test data of three gassy sands shows that the new model can capture the constitutive behavior of gassy marine sand over a wide range of initial states and degrees of saturation (typically between 85% and 100% for unsaturated marine sediments) using a single set of parameters. Parametric studies were performed to quantify the effects of gas (either ‘detrimental’ or ‘beneficial’) on sand with various initial states. The new model has been implemented in ABAQUS and used to simulate the stability of submarine slopes under undrained loading condition. It is found that free gas can improve and weaken the slope stability for loose and dense sand, respectively.

中文翻译：

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粗粒含气土的状态相关本构模型及其在边坡失稳建模中的应用

摘要 海洋砂质沉积物中游离气体在世界范围内普遍存在。含气砂的一个显着特点是，在不排水剪切作用下，孔隙流体中存在的吸留气泡可以增加相对松散状态下砂的不排水强度，而降低相对致密砂的强度。以前的理论分析主要集中在模拟游离气体在迁移静态液化过程中对松散砂土的“有利”影响，很少尝试描述在不排水载荷下气体对致密砂土的“不利”影响。本研究提出了一个状态相关的临界状态模型，它以统一的方式描述了不同状态下含气砂的不同行为。三种含气砂岩的模型预测和测试数据的比较表明，新模型可以捕捉到含气海砂在较宽的初始状态和饱和度范围内（对于不饱和海相沉积物通常在 85% 到 100% 之间）的本构行为使用一组参数。进行参数研究以量化气体（“有害”或“有益”）对具有各种初始状态的沙子的影响。新模型已在ABAQUS中实现，用于模拟不排水荷载条件下海底边坡的稳定性。发现游离气对松散砂土和致密砂土分别具有改善和削弱边坡稳定性的作用。