Collaborative Research: Novel Measurement of Shear Strength Evolution in Liquefied Soil and Calibration of a Fluid Dynamics-based Constitutive Model for Flow Liquefaction

合作研究：液化土中剪切强度演变的新测量以及基于流体动力学的流动液化本构模型的校准

• 批准号: 1728199
• 负责人: Scott Olson
• 金额: $ 30.48万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1728199&HistoricalAwards=false
• 关键词: Collaborative; Research; Novel; Measurement; Shear

Countless hydraulic fill and tailings dams, levees, and other slopes contain loose soils with little or no internal cohesion. This state renders them vulnerable to failures under seismic events in which the soil becomes "liquefied." Although large flow failures of such earth structures are uncommon, the catastrophic consequences of such failures dramatically elevate the associated risk. Modeling this behavior requires reliable estimates of how the strength of a liquefying soil evolves to its minimum as internal water pressures are generated during an earthquake. Of equal importance is understanding how the soil subsequently regains its strength as water pressures dissipate once shaking ceases. To date, there are no full-scale field measurements of this strength evolution to guide model development; therefore, engineers must rely on strength estimates calculated after the fact from sparse, poorly documented flow failure case histories. The uncertainty in selecting design values of residual strength is exacerbated if the soil contains significant amount of fine particles, as each empirical method suggests a different approach to account for fines. This project will provide practicing engineers a better understanding of the large-strain behavior of liquefiable soils, improved estimates of residual shear strength, and new calibrated modeling tools that are required to make crucial decisions on high-risk, high-consequence projects involving tens or even hundreds of millions of dollars. The project's education and technology transfer plan includes training and mentoring graduate and undergraduate students from multiple disciplines (geotechnical, mechanical, and electrical engineering, as well as fluid dynamics).This interdisciplinary project centers on developing a potentially transformative understanding of the shearing resistance of liquefiable soils (including its evolution during pore pressure generation, residual strength mobilization, and pore pressure dissipation) in an environment with greater realism than available in conventional laboratory tests. Specifically, novel centrifuge models will utilize a thin metal coupon (plate) pulled through a liquefiable soil before, during, and after shaking to directly measure the soil's residual strength and strength recovery. By embedding a pressure transducer in the coupon, it will be possible for the first time to measure pore pressures directly on the shearing surface in a liquefied soil. The large number of measurements will allow the researchers to explore the effects of fines content (soil compressibility), effective stress, and strain rate on residual strength. Cone penetration resistance and shear wave velocity will be measured in-situ in the centrifuge models, allowing the researchers to validate or improve empirical residual strength correlations. In turn, the physical measurements from the centrifuge testing program will enable the researchers to calibrate a multi-disciplinary, fluid dynamics-based stress-strain constitutive model for evaluating liquefaction problems such as flow slides, debris flows and lateral spreading around pile foundations. This project will utilize the NHERI Centrifuge facility at the University of California, Davis.

无数的水力充填和尾矿坝、堤坝和其他斜坡都含有松散的土壤，这些土壤几乎没有或根本没有内部凝聚力。 这种状态使得它们在地震事件下容易发生故障，其中土壤变得“液化”。“虽然这种地球结构的大流量故障是罕见的，这种故障的灾难性后果显着提高了相关的风险。 对这种行为进行建模需要可靠地估计，当地震期间产生内部水压力时，膨胀土的强度如何演变到最小值。 同样重要的是了解土壤如何在震动停止后随着水压消散而恢复其强度。 到目前为止，还没有全尺寸的现场测量的强度演变，以指导模型的开发，因此，工程师必须依赖于强度估计计算后，从稀疏的，缺乏记录的流动故障的情况下的历史。 如果土壤中含有大量的细颗粒，则剩余强度设计值选择的不确定性会加剧，因为每种经验方法都建议采用不同的方法来考虑细颗粒。 该项目将为执业工程师提供更好地了解可液化土壤的大应变行为，改进剩余剪切强度的估计，以及新的校准建模工具，这些工具需要对涉及数千万甚至数亿美元的高风险，高后果项目做出关键决策。该项目的教育和技术转让计划包括培训和指导来自多个学科的研究生和本科生（岩土工程，机械和电气工程，以及流体动力学）。这个跨学科的项目中心发展的潜在变革性的理解可液化土壤的抗剪性（包括孔隙压力产生、残余强度动员和孔隙压力消散过程中的演变）。 具体而言，新型离心机模型将利用薄金属试样（板）通过可液化土壤之前，期间和之后的震动，直接测量土壤的残余强度和强度恢复。通过在试样中嵌入压力传感器，将首次有可能直接测量液化土壤中剪切表面上的孔隙压力。 大量的测量将使研究人员能够探索细粒含量（土壤压缩性），有效应力和应变率对残余强度的影响。 锥贯入阻力和剪切波速将在离心机模型中进行现场测量，使研究人员能够验证或改进经验剩余强度相关性。 反过来，离心测试计划的物理测量将使研究人员能够校准多学科的基于流体动力学的应力-应变本构模型，用于评估液化问题，如流动滑坡，泥石流和桩基周围的横向扩散。 该项目将利用位于戴维斯的加州大学的NHERI实验室设施。

项目成果

Overburden Normalization for In-Flight Centrifuge Miniature Cone Penetration Testing in Sand

沙中飞行离心机微型锥体贯入测试的覆盖层归一化

• DOI: 10.1061/9780784484036.024
• 发表时间: 2022
• 期刊: Geo-Congress 2022
• 作者: Chen, Jiarui;Olson, Scott M.;Banerjee, Soham;Dewoolkar, Mandar M.;Dubief, Yves
• 通讯作者: Dubief, Yves

Effect of shear strain rate on undrained shearing resistance of a clean silica sand measured in direct simple shear tests.

直接简单剪切试验中测量的剪切应变率对洁净硅砂不排水抗剪强度的影响。

• 发表时间: 2020
• 期刊: Tailings and Mine Waste '20
• 作者: Chen, J.

Water Content of Moist-Tamped Nonplastic Specimens for Constant-Volume Direct Simple Shear Testing

用于恒体积直接简单剪切试验的湿压实非塑料试样的含水量

• DOI: 10.1520/gtj20210125
• 发表时间: 2022
• 期刊: Geotechnical Testing Journal
• 影响因子: 1.6
• 作者: Chen, Jiarui;Olson, Scott M.;Banerjee, Soham;Dewoolkar, Mandar M.;Dubief, Yves
• 通讯作者: Dubief, Yves