考虑孔径和物化特性的胶结型能源黏土离散元模拟方法
A discrete element simulation method of clayey grain-cementing type methane hydrate bearing sediment accounting for pore size and physicochemical properties
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摘要: 甲烷水合物是重要的清洁能源，广泛分布于我国南海的黏质储层（能源黏土）中。能源黏土的力学行为受多场影响(温度-反压-化学)和多种因素(孔径-水合物饱和度-黏土物化特性)的影响，力学特性复杂。研发能反映能源黏土在复杂应力路径下力学响应的数值分析方法，对我国甲烷水合物安全开采至关重要。本文首先引入水化学势建立了考虑孔径和黏土物化学特性影响的水合物强度、刚度半理论公式，并将这一公式引入到结构性黏土的接触模型中，建立了考虑孔径和物化特性影响的胶结型能源黏土接触模型。并在离散元模拟过程中通过初始组构参数建立了孔径的识别方法，将计算得到的孔径与接触模型关联，模拟了等向压缩试验、常规三轴试验和真三轴试验，分析了胶结型能源黏土的压缩特性，强度和剪切特性的影响，并与现有研究成果进行对比，结果表明离散元模拟得到的试验结果与室内试验结果一致。离散元模拟结果分析表明较高的水合物饱和度和含水率，较低的温度均会增大胶结型能源黏土的屈服强度和峰值强度，较高的水合物饱和度会显著增强能源黏土的剪胀性，且硬（软）化规律和临界状态强度与中主应力系数密切相关。Abstract: Methane hydrate (MH) is an important clean energy resource, widely distributed in clayey type methane hydrate bearing sediment (MHBS) in the South China Sea. The mechanical behavior of clayey type MHBS is affected by many factors, such as temperature field, back pressure field, chemical fields, pore size, MH saturation, physicochemical properties of clay, which is significantly different from that of sandy type MHBS. Therefore, the development of numerical analysis methods reflecting the mechanical response of clayey type MHBS under complex stress paths is crucial for the safe exploitation of MH.
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