Critical State of Sands Revisited: Fabric Effects

临界状态土力学（CSSM）是土本构模型的一个框架。从一个重要的缺失因素的角度来看，这一范式将受到建设性的挑战：土壤结构，特别是沙子，对临界状态的前提和条件的影响。假设织物的特征是一个适当定义的织物张量，代表粒子的方向分布，接触法线或空隙矢量，向临界状态值演化，将通过离散颗粒力学（DEM）和连续介质力学方法进行研究。主要目标将是通过一个额外的临界状态织物条件来增强应力和空隙比的临界状态条件，将结果纳入新的织物增强CSSM本构框架，并通过实例说明织物对本构的影响以及地质力学边值问题的数值模拟。了解砂土在变形和应力作用下的响应，对岩土结构的安全设计和分析具有重要意义。现有的最主要的理论框架，临界状态土力学，需要加强，以解释与土壤颗粒在自然沉积过程中定向方式相关的特定方面。该项目将通过离散粒子建模模拟和随后的连续介质力学方法来解决这些问题。这一成功的成果将极大地改变CSSM理论在大学的教学方式和在岩土工程实践中的应用，这一领域在减轻与地震和滑坡有关的危害方面具有越来越大的社会影响。它还将为颗粒物理和材料科学的邻近领域提供工程视角，在这些领域，连续体工程方法对织物效果非常有用。这些发现将被整合到一个教育计划中，导致向年轻学生介绍最简单方面的研讨会和研究生课程的发展。拟议的研究结果将通过讲习班、档案刊物的出版物和在会议上的发言加以传播。

Critical State Soil Mechanics (CSSM) is the paradigm of a framework for soil constitutive modeling. This paradigm will be constructively challenged from the perspective of one important missing factor: the effect of soil fabric, in particular sands, on the premises and conditions characterizing critical state. The hypothesis that the fabric, characterized by an appropriately defined fabric tensor representing the orientational distribution of particles, contact normals or void vectors, evolves towards a critical state value will be investigated by means of discrete granular mechanics (DEM) and continuum mechanics methods. The main objective will be the enhancement of the critical state conditions for stress and void ratios by one additional condition for critical state fabric, the incorporation of the results into a new fabric-enhanced CSSM constitutive framework, and the illustration by examples of fabric effects on constitutive and numerical modeling of Geomechanics boundary value problems. Understanding the sandy soil response when deformed and stressed, is of fundamental importance for the safe design and analysis of geotechnical structures. The existing famework of the most predominant theory, Critical State Soil Mechanics, is in need of an enhancement to account for particular aspects related to the way the soil particles are oriented during their natural deposition process. The project will adress these issues by means of discrete particles modeling simulations and ensuing continuum mechanics methodologies. The successful outcome will drastically change the way CSSM theory is taught at Universities and applied in geotechnical practice, a field of increasing social impact in regards to hazard mitigations related to earthquakes and landslides. It will also offer an engineering perspective to the neighboring fields of granular physics and material sciences, where a continuum engineering approach to fabric effects can be very useful. Such findings will be integrated into an educational program leading to seminar presentations of the simplest aspects to young students and the development of graduate courses. The results of the proposed study will be disseminated through workshops, publications in archival journals and presentations at conferences.