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: 1728172
• 负责人: Mandar Dewoolkar
• 金额: $ 37.73万
• 依托单位: University of Vermont & State Agricultural College
• 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=1728172&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.

无数的液压填充和尾矿大坝，堤坝和其他斜坡含有很少或没有内部内聚力的松散土壤。 这个国家使它们在地震事件中容易受到土壤“液化”的地震事件的失败。 尽管这种地球结构的大量失败并不常见，但这种失败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的估计，即随着地震期间内部水压产生，液化土壤的强度如何发展到最小值。 同样重要的是，一旦摇动一旦颤抖，土壤随后如何恢复其强度。 迄今为止，没有这种强度演变的全尺度现场测量来指导模型开发。因此，工程师必须依靠在稀疏，文献较差的流量故障案例历史中计算出的强度估计值。 如果土壤包含大量的细颗粒，选择残余强度的设计值的不确定性会加剧，因为每种经验方法都提出了一种考虑罚款的不同方法。 该项目将为实践工程师更好地了解液化土壤的大稳定行为，改进的剩余剪切强度的估计值以及新的校准建模工具，这些工具是对高风险，高风险项目的重要决策所必需的，这些项目涉及数十千万美元。该项目的教育和技术转移计划包括来自多个学科的培训和指导毕业生和本科生（岩土，机械，机械和电气工程以及流体动力学）。该项目集中于对液化土壤的剪切抗性（包括在孔内压力上的越来越多）中的潜在变革性理解（包括在孔内压力上的进化），并在孔内压力上的进化，以及在孔中的进化，以及在孔中的进化，并在孔中的进化，以及孔孔，孔在孔中的进化，以及孔培养物的进化，以及孔孔，孔在孔中的进化，以及孔的孔子，培养在孔中，并构成了孔内的动作，并构成了孔子的进化。常规实验室测试。 具体而言，新型离心机模型将利用薄金属优惠券（板），然后在摇动之前，之中和之后直接测量土壤的剩余强度和强度恢复。通过将压力传感器嵌入息票中，首次有可能在液化土壤中直接在剪切表面上测量孔隙压力。 大量测量将使研究人员能够探索罚款含量（土壤可压缩性），有效应力和应变率对残余强度的影响。 在离心机模型中，将测量锥体穿透性抗性和剪切波速度，从而使研究人员能够验证或改善经验的残留强度相关性。 反过来，离心测试程序的物理测量结果将使研究人员能够校准基于基于流体动力学的多学科，基于流体动力学的应力 - 应变组构型模型，以评估液化问题，例如流动幻灯片，碎屑流和围绕桩基础的横向扩散。 该项目将利用加利福尼亚大学戴维斯分校的NHERI离心机设施。

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

Computational fluid dynamics-based modeling of liquefied soils

基于计算流体动力学的液化土壤建模

• 发表时间: 2019
• 期刊: 7 ICEGE 2019 - International Conference on Earthquake Geotechnical Engineering
• 作者: Banerjee, S.

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