NEESR Payload: Measurement of the Strength of Liquefied Soil in Physical Models

NEESR 有效负载:物理模型中液化土强度的测量

基本信息

项目摘要

This research is an outcome of the National Science Foundation 07-506 program solicitation "George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research" competition. This project is a payload to National Science Foundation award 0530478, "NEESR-GC: Seismic Risk Mitigation for Port Systems," and will utilize the tests being conducted by award 0530478 in the NEES geotechnical centrifuge at the University of California, Davis. This project is led by the University of Vermont and includes a subaward to the University of New Hampshire. It has long been observed that saturated sands subjected to shock or earthquake loading experience drastic loss of strength and behave as heavy fluids, gradually regaining strength as internal water pressures dissipate. As long as the liquefied state persists, the soil will flow down slopes, producing destructive landslides and large drag forces on obstacles such as piled foundations. Modeling this behavior for risk studies and engineering design, however, requires adequate measurements of how shearing strength loss and its eventual recovery evolve as internal water pressures build up and subsequently dissipate. There are currently no full-scale field measurements of these strength changes to guide development of such models; existing field case histories are limited to observing the final damage produced by the liquefaction process. Controlled laboratory measurements would be desirable, but the onset of liquefaction is accompanied by such large strains that soil samples in conventional laboratory tests become so drastically deformed that reliable strength measurements can no longer be made. As a first step in measuring the evolving behavior of liquefied sands, it is envisioned that the shear strength of liquefying sand can be measurable in-flight in the NEES geotechnical centrifuge model using a thin coupon (plate, about 25 millimeters by 25 millimeters by 1.5 millimeters) pulled horizontally through the soil model, with its major dimensions parallel to the base of the model. The large strains and strain rates associated with liquefaction flow failures would thus be simulated by moving the coupon relative to the sand, through and after the shaking until the excess pore pressures dissipate. By measuring the drag force on the coupon, it will be possible to observe the evolution of the soil shear strength as it decreases to a minimum (residual strength) and subsequently increases as pore pressures dissipate. The centrifuge models will provide realistic field-scale stresses and boundary conditions, and the dense array of instrumentation will facilitate observations to be made on the strength changes in the liquefying sand from beginning to end of simulated earthquakes. The results would also be used to validate companion ring shear and modified cyclic triaxial testing. The combined results of a series of centrifuge and small-scale laboratory experiments will provide guidance on how to simulate the large-scale tests in smaller laboratory apparatus, thus making it easier to study the behavior of other soil types, such as silty and clayey sands, during liquefaction both for general studies and for specific engineering design purposes. A simple yet rational model for predicting the rate-dependent evolution of shearing strength of granular soils as pore pressures build up and the soil mass deforms will be developed. This will permit more accurate simulation of such problems as estimating the forces exerted by liquefied soil on obstacles like pile-supported structures, and the prediction of flow slide behavior in general. These results are expected to give designers enhanced understanding of how to choose residual strength values for remediation of earth structures. Equipment required to conduct the payload tests will be designed and built by a group of undergraduate mechanical and electrical engineering students at the University of Vermont as their senior capstone design project, and calibrated before installation by a civil engineering undergraduate student. The companion ring shear and modified cyclic triaxial tests will be carried out by a civil engineering graduate student at the University of New Hampshire. Data from this project will be archived in the NEES data repository (http://www.nees.org).
本研究是美国国家科学基金会07-506项目“乔治E。小布朗地震工程模拟研究网络(NEES)竞赛。 该项目是美国国家科学基金会0530478号奖“NEESR-GC:港口系统地震风险缓解”的有效载荷,并将利用加州大学戴维斯分校NEES土工离心机中的0530478号奖进行的测试。 该项目由佛蒙特大学领导,包括一个分奖给新罕布什尔州大学。 长期以来,人们已经观察到,受到冲击或地震荷载的饱和砂土强度急剧下降,表现为重流体,随着内部水压力的消散,逐渐恢复强度。只要液化状态持续,土壤就会沿着斜坡向下流动,产生破坏性的山体滑坡,并对桩基础等障碍物产生巨大的拖曳力。然而,为风险研究和工程设计建模这种行为需要充分测量剪切强度损失及其最终恢复如何随着内部水压力的建立和随后的消散而演变。目前还没有这些强度变化的全尺寸现场测量来指导此类模型的开发;现有的现场案例历史仅限于观察液化过程产生的最终损害。受控的实验室测量是可取的,但液化的开始伴随着如此大的应变,以至于传统实验室测试中的土样变得如此剧烈地变形,以至于不再能进行可靠的强度测量。作为测量液化砂演变行为的第一步,可以设想,在NEES土工离心模型中,可以使用水平穿过土壤模型的薄试样(板,约25 mm × 25 mm × 1.5 mm)在飞行中测量液化砂的剪切强度,其主要尺寸平行于模型的底部。因此,通过相对于砂土移动试样,在整个振动过程中和振动后,直到多余的孔隙压力消散,可以模拟与液化流破坏相关的大应变和应变率。通过测量试样上的拖曳力,可以观察土壤剪切强度的演变,因为它降低到最小值(剩余强度),随后随着孔隙压力的消散而增加。离心模型将提供真实的现场规模的应力和边界条件,密集的仪器阵列将有助于观察模拟地震从开始到结束的流沙强度变化。试验结果也可用于验证环剪试验和改进的循环三轴试验。一系列离心和小规模实验室试验的综合结果将为如何在较小的实验室设备中模拟大规模试验提供指导,从而使研究其他土壤类型(如粉质和粘性砂)在液化过程中的行为更容易,无论是一般研究还是特定的工程设计目的。一个简单而合理的模型,预测率依赖的孔隙压力建立和土体变形的粒状土壤的抗剪强度的演变。这将允许更准确地模拟这样的问题,如估计力施加的液化土壤上的障碍物,如桩支撑结构,并预测一般的流滑行为。 预计这些结果将使设计人员更好地了解如何选择剩余强度值修复土结构。 进行有效载荷测试所需的设备将由佛蒙特大学的一组机械和电气工程专业的本科生设计和建造,作为他们的高级顶点设计项目,并在安装之前由土木工程专业的本科生进行校准。将由新罕布什尔州大学的一名土木工程研究生进行同伴环剪切和改进的循环三轴试验。 该项目的数据将存档在NEES数据存储库(http://www.example.com)中。www.nees.org

项目成果

期刊论文数量(0)
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会议论文数量(0)
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Mandar Dewoolkar其他文献

Rate-dependent interfacial adhesive strength and toughness between aggregates and modified asphalt binders in ambient conditions
环境条件下集料与改性沥青结合料之间与速率相关的界面粘结强度和韧性
  • DOI:
    10.1016/j.molliq.2025.127679
  • 发表时间:
    2025-07-01
  • 期刊:
  • 影响因子:
    5.200
  • 作者:
    Shuliang Wang;Junjie Zhang;Fan He;Jiehao Feng;Chuanhai Wu;Zhixiang Wang;Fulian Chen;Saleh Alghamdi;Yuanyuan Zheng;Fen Du;Dryver Huston;Mandar Dewoolkar;Ting Tan
  • 通讯作者:
    Ting Tan
Inferring apparent Newtonian viscosities of liquefied soils from physical models – Analysis using computational fluid dynamics
  • DOI:
    10.1016/j.soildyn.2024.109170
  • 发表时间:
    2025-03-01
  • 期刊:
  • 影响因子:
  • 作者:
    Soham Banerjee;Yves Dubief;Mandar Dewoolkar;Jiarui Chen;Scott Olson
  • 通讯作者:
    Scott Olson

Mandar Dewoolkar的其他文献

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{{ truncateString('Mandar Dewoolkar', 18)}}的其他基金

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
  • 财政年份:
    2017
  • 资助金额:
    --
  • 项目类别:
    Standard Grant
MRI: Acquisition of a High Energy X-ray Tomography Scanner
MRI:获取高能 X 射线断层扫描仪
  • 批准号:
    1429252
  • 财政年份:
    2014
  • 资助金额:
    --
  • 项目类别:
    Standard Grant

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