CPT-Based Characterization of Intermediate Soils

评价中间土的性质和强度，例如粉砂、粘土砂、桑迪粉土、桑迪粘土和低塑性粉土，仍然是岩土工程和地质工程中最普遍和最不确定的挑战之一。 技术文献中充满了估计强度的程序（例如，排水和不排水，单调和循环），但其扩展到中间土壤往往缺乏健全的理论基础，并涉及经验插值的数据，从砂和粘土与中间土壤的直接数据很少。 本研究将直接解决这个不足之处，开发和验证一个基于力学的框架，建立锥贯入阻力，原位应力，状态参数和特定的土壤性质，如单调强度和循环阻力比（CRR）之间的相互关系，使用实验室元件测试，数值模拟锥贯入，离心模型试验相结合。 实验室试验，包括极限压缩，直接简单剪切，和三轴，将被用来表征九种不同的土壤混合物跨越广泛的土壤级配和细粉塑性的特性。 大应变过程的锥贯入将在FLAC中进行建模，通过实施任意拉格朗日-欧拉（ALE）重新网格化技术，并使用广义本构模型MIT-S1，后者已被证明可以准确地模拟土壤的行为，从砂，中间土，粘土。 在根据公布的数据集进行验证后，将对所有土壤混合物进行数值模拟。 带有飞行中锥体探测和动态震动的模型试验将能够进一步验证锥体贯入度的数值模拟，根据实验室元件试验提供预期循环强度的独立确认，并提供动态现场响应和相关动态和永久地面变形的数据。 实验和数值模拟数据将被用来开发和评估锥贯入试验数据和土壤性质之间的各种功能相互关系。这项研究将直接解决基本需要的力学为基础的框架，以推进和改造的方式，中间土壤强度和其他属性估计从静力锥贯入试验数据。 这项工作将通过整合实验室，离心机和数值模拟组件来提高理解和知识，以解决以前没有系统解决的问题。 潜在的研究结果将适用于广泛的岩土工程和地质问题，包括与建立在中间土壤上或由中间土壤建造的任何地球结构或民用基础设施系统的静态和地震响应相关的问题。 基于科学的广义锥解释方法有可能改变研究生院和专业课程中提供的技术培训，并减少在实践中面对工程不确定性时采取的代价高昂的保守主义。 这项研究将有助于研究生的发展，使他们能够在学术界或工业界取得成功的职业生涯，使K-12学生接触岩土工程和地震工程方面，并为一群高中教师提供地球科学模块的培训，以满足他们的课程需求。

Evaluating properties and strengths of intermediate soils, such as silty sands, clayey sands, sandy silts, sandy clays, and low-plasticity silts, remains one of the most pervasive and uncertain challenges in geotechnical and geological engineering. Technical literature is full of procedures for estimating strengths (e.g., drained and undrained, monotonic and cyclic) of clean sands and sedimentary clays, but their extension to intermediate soils often lacks a sound theoretical basis and involves empirical interpolation of data from sands and clays with little direct data for intermediate soils. This research will directly address this deficiency by developing and validating a mechanics-based framework for establishing inter-relationships between cone penetration resistance, in-situ stresses, state parameter, and specific soil properties such as monotonic strengths and cyclic resistance ratios (CRR) using a combination of laboratory element tests, numerical simulations of cone penetration, and centrifuge model testing. Laboratory tests, including limiting compression, direct simple shear, and triaxial, will be used to characterize the properties of nine different soil mixtures spanning a broad range of soil gradations and fines plasticity. The large-strain process of cone penetration will be modeled in FLAC by implementing an Arbitrary Langrangian-Eulerian (ALE) remeshing technique and using the generalized constitutive model MIT-S1, the latter of which has been shown to accurately model the behavior of soils ranging from sands, to intermediate soils, to clays. Numerical simulations will be performed for all soil mixtures, after validation against published data sets. Centrifuge model tests with in-flight cone soundings and dynamic shaking will enable further validation of the numerical simulations of cone penetration, provide independent confirmation of cyclic strengths expected on the basis of the laboratory element tests, and provide data on dynamic site response and the associated dynamic and permanent ground deformations. The experimental and numerical simulation data will then be used to develop and evaluate various functional inter-relationships between the cone penetration test data and soil properties. This research will directly address the essential need for a mechanics-based framework to advance and transform the way intermediate soil strengths and other properties are estimated from cone penetration test data. The work will advance understanding and knowledge by integrating laboratory, centrifuge, and numerical simulation components to address a topic that has not previously been systematically addressed. The potential findings will be applicable across a broad spectrum of geotechnical and geological problems, including issues associated with the static and seismic responses of any earth structure or civil infrastructure system founded on, or constructed of, intermediate soils. A science-based generalized cone interpretation method has the potential to transform the technical training provided in graduate schools and professional courses, and reduce costly conservatisms adopted in the face of engineering uncertainty in practice. The study will contribute to the development of graduate students with broad integrative training that equips them for successful careers in academia or industry, exposure K-12 students to aspects of geotechnical and earthquake engineering, and provide training for a group of high school teachers on earth science modules that address their curricular needs.