A unified framework for engineering characterization of argillaceous formations (soils and rocks)

泥质建造是最丰富的沉积土壤和岩石类型，根据不同的估计，占整个沉积建造柱的45%到55%。含有粉砂或粘土大小的颗粒或粘土矿物的泥质地层可以是未胶结的(硬粘土和硬粘土)，也可以是硬化的(页岩、泥岩、粉砂岩和泥岩)。由于泥质地层的丰富性和工程性质的多样性，给岩土界(例如基础、斜坡稳定性和地下开挖)和能源部门(例如完井、储层围堵和水力压裂)带来了许多挑战。所有这些泥质地层都是粘土、泥浆和粉砂的复合等价物，具有不同程度的固结或胶结(硬化)。它们的工程性质取决于组分类型、组成、粒度分布、排列和胶结作用。以往对泥质地层的研究大多是针对特定地点进行的。基于简单的物理测试和指数(如粘土含量、液体和塑性极限)，对不同地点的泥质地层进行了经验关联。这些经验关联没有科学发展的余地，也没有限制在工程实践中使用的空间。这项拟议研究计划的长期目标是为泥质地层(土壤和岩石)的工程表征开发一个统一的框架。该框架将建立在理解和量化泥质地层的纳米和微观结构的基本物理以及复合材料与实际应用中遇到的环境变化的相互作用的基础上。先进的成像和显微技术将被用来在纳米和微观水平上表征泥质地层结构。将在实验室开发创新的方法，在实际应用中评价泥质地层在高温、压力、应力和化学梯度条件下的行为和表现。这一研究项目的成果可以很容易地转移到上述本构模型、数值模拟和设计方面的其他研究和实践活动中。**

Argillaceous formations are the most abundant sedimentary soil and rock types, varying according to different estimates from 45 to 55% of the total sedimentary formation column. The argillaceous formations containing silt- or clay-sized particles or clay minerals could be uncemented (stiff clays and hard clays) or hardened (shales, argillites, siltstones, and mudstones). Due to their abundance and variation in engineering properties, the argillaceous formations impose many challenges on the geotechnical community (e.g., foundation, slope stability, and underground excavation) and energy sector (e.g., well completion, reservoir containment, and hydraulic fracturing). ***    All these argillaceous formations are composite equivalents of clays, muds, and silts, with varying degree of consolidation or cementation (induration). Their engineering properties depend on constituent type, composition, size distribution, arrangement, and cementation. Most of previous research investigations on argillaceous formations are very site specific. Empirical correlations based on simple physical tests indices (such as clay content, liquid and plastic limits) have been made among argillaceous formations from different sites. These empirical correlations have no room for scientific development and limiting use in engineering practices. The long-term goal of this proposed research program is development of a unified framework for engineering characterization of argillaceous formations (soils and rocks). The framework will be built on understanding and quantifying the fundamental physics of the nano- and micro-structures of the argillaceous formations, and the interaction of the composite materials with the environmental changes encountered in practical applications. Advanced imaging and microscopy techniques will be used in characterizing the argillaceous formation structure in nano- and micro-levels. Innovative methodologies will be developed in laboratory to evaluate the behavior and performance of argillaceous formations under high temperature, pressure, stress and chemical gradient conditions in practical applications. The findings from this research program can be readily transferred to other research and practical activities listed above in terms of constitutive modelling, numerical simulation and design. **