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CPT-Based Characterization of Intermediate Soils

基于 CPT 的中质土表征

基本信息

批准号：
1300518
负责人：
Ross Boulanger
金额：
$ 49.8万
依托单位：
University of California-Davis
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2013
资助国家：
美国
起止时间：
2013-09-01 至 2017-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1300518&HistoricalAwards=false
关键词：
CPT Based Characterization Intermediate Soils

项目摘要

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.

评价粉质砂土、粘性砂土、砂质粉土、砂质粘土和低塑性粉土等中间土的性质和强度，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。技术文献中充斥着估算清洁砂土和沉积粘土的强度(如排水和不排水、单调和循环)的程序，但将其推广到中间土往往缺乏可靠的理论基础，并且涉及到对来自砂和粘土的数据进行经验内插，而中间土的直接数据很少。这项研究将通过开发和验证基于力学的框架来直接解决这一不足，该框架用于建立锥体贯入阻力、地应力、状态参数和特定土属性之间的相互关系，例如单调强度和循环阻力比(CRR)，使用实验室单元试验、锥体贯入的数值模拟和离心机模型试验的组合。实验室测试，包括极限压缩、直接简单剪切和三轴试验，将被用来表征跨越广泛的土级配和细微塑性的九种不同的土壤混合物的特性。通过采用任意拉格朗日-欧拉(ALE)重网格技术和广义本构模型MIT-S1，将在FLAC中模拟锥体侵彻的大应变过程，后者已被证明能够准确地模拟从砂土到中间土再到粘土的各种土的特性。在与已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。利用飞行中的锥体测深和动态振动进行的离心机模型试验将进一步验证锥体贯入的数值模拟，提供基于实验室单元测试的预期循环强度的独立确认，并提供关于场地动态响应以及相关的动态和永久地面变形的数据。然后，将使用试验和数值模拟数据来建立和评估圆锥贯入试验数据和土壤性质之间的各种函数相互关系。这项研究将直接解决以力学为基础的框架的基本需求，以推进和改变从圆锥贯入试验数据估计中间土强度和其他特性的方式。这项工作将通过整合实验室、离心机和数值模拟组件来促进理解和知识，以解决以前没有系统解决的问题。这些潜在的发现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反应有关的问题。以科学为基础的广义圆锥解释方法有可能改变研究生院和专业课程提供的技术培训，并减少在面对实践中的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，为他们在学术界或工业领域的成功职业生涯做好准备，让K-12学生接触到岩土工程和地震工程的各个方面，并为一批高中教师提供关于地球科学模块的培训，以满足他们的课程需求。