EAGER: Exploration of an Interdisciplinary Approach to Resolving a Critical Issue in Evaluating Liquefaction Hazard of Challenging Soil Sites

EAGER：探索跨学科方法来解决评估具有挑战性的土壤场地液化危险的关键问题

• 批准号: 1937984
• 负责人: Alba Yerro Colom
• 金额: $ 15.8万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-01 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1937984&HistoricalAwards=false
• 关键词: EAGER; Exploration; Interdisciplinary; Approach; Resolving

This EArly-concept Grant for Exploratory Research (EAGER) project focuses on developing computational methods to improve the accuracy and resolution of data used to study earthquake-induced liquefaction risk at challenging soil sites. Liquefaction is the process by which loose, sandy soils lose their strength during earthquake shaking, causing significant damage. This research will help optimize efforts to mitigate liquefaction risk by improving the current methods for liquefaction hazard assessment, resulting in a benefit for society at large, worldwide. The specific focus will be improving the accuracy and resolution of data from cone penetration test (CPT) soundings, a common method for geotechnical engineers to develop a depth profile of the soil properties. CPT soundings provide measured profiles of tip resistance and side friction experienced by a pointed instrument called a penetrometer as it is pushed into the ground. However, the measured resistance and friction represents the influence of a volume of soil surrounding the penetrometer. Thus, CPT data are "smoothed" or "blurred" by the physics of the measurement procedure. This is problematic when engineers attempt to locate thin layers of soil, which might be "smoothed out," but that are critical to understanding liquefaction mechanisms and risk. Advanced computational models and optimization techniques from imaging science will be used to "deblur" these data. If successful, this research will result in robust and efficient computational framework and associated software that corrects data to resolve thin subsurface layers. The improvements in resolution and reliability will ideally allow geotechnical engineers to identify thin layers in the subsurface that were not previously identifiable. This will represent a significant methodological advance, enabling studies of the fundamental role of thin layers in liquefaction. The results from this research will be of direct interest to the profession, and the adoption of the research findings by the profession will be expedited by the Co-PIs' involvement in the Center for Geotechnical Research and Practice at Virginia Tech. This interdisciplinary project will support two Virginia Tech graduate student researchers, one in mathematics and one in civil engineering. Co-PI R. Green has established an outreach program for military veterans and has to date recruited three veterans in his research group. The PI and CoPIs will use this project to further this effort in working with veterans. Comparison of predicted versus observed severity of surficial liquefaction manifestations at sites comprised of sandy soils with interbedded silt and clay layers during the 2010-2011 Canterbury, New Zealand earthquake sequence (CES) highlights significant limitations of currently used liquefaction evaluation procedures. One potential issue is the limitation of CPT to identify and properly characterize thin layers that impact the liquefaction response of the entire profile. Multiple interbedded layers have a "smoothing" effect on the measured CPT tip resistance and sleeve friction, resulting in significant underestimation of the density of sand layers and an overestimation of the stiffness of fine-grained layers. While procedures have been suggested to correct CPT tip resistance for "thin layer effects," most of these procedures are manual and are not applicable for multiple thin layer effects. A recent procedure was developed to account for multiple thin layer effects by posing it as an inverse problem, assuming the measured CPT data equal the "true" CPT data convolved with a depth-dependent spatial filter following a simple 1D model (Boulanger and DeJong, 2018), but our analysis indicates this procedure cannot correct for thin layers at the scale of interest (e.g., layers of a few centimeters or thinner), and is often slow to converge, if convergence is achieved at all. Furthermore and more significantly, when applied to a large database of liquefaction case histories from the CES, the procedure yields, in totality, less accurate predictions than if no thin layer corrections were applied to the CPT soundings. The objective of this project is to explore an interdisciplinary approach to resolving this critical issue in evaluating liquefaction hazard of challenging soil sites (i.e., sand soil profiles having multiple, thin interbedded layers of non-liquefiable soil). A robust, computationally scalable technique will be developed to invert for "true" Cone Penetration Test (CPT) sounding data (i.e., correct for multiple thin layer effects) for these sites that is based on the total variational (TV) minimization method. To assess the efficacy of the developed inversion algorithm, the Material Point Method (MPM) will be used to simulate CPT performed in challenging soil profiles that have a range of characteristics of interest; the MPM model will first be validated against calibration chamber test data. This will allow us to know both the ?true? and ?measured? CPT sounding data for the multiple interbedded layer profiles.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

EARLY概念探索性研究资助（EAGER）项目的重点是开发计算方法，以提高用于研究具有挑战性土壤场地地震诱导液化风险的数据的准确性和分辨率。 液化是松散的桑迪土壤在地震震动中失去强度的过程，造成重大破坏。 这项研究将有助于通过改进目前的液化危险评估方法来优化减轻液化风险的努力，从而使全世界的社会受益。 具体的重点将是提高锥贯试验（CPT）测深数据的准确性和分辨率，这是岩土工程师开发土壤特性深度剖面的常用方法。 CPT探测提供了尖端阻力和侧摩擦力的测量剖面，这些阻力和侧摩擦力是由一种称为压力计的尖端仪器在被推入地下时所经历的。 然而，所测量的阻力和摩擦力代表了土阻计周围土壤体积的影响。 因此，CPT数据被测量过程的物理学“平滑”或“模糊”。 当工程师试图定位可能被“平滑”的薄层土壤时，这是有问题的，但这对理解液化机制和风险至关重要。 来自成像科学的先进计算模型和优化技术将用于“去模糊”这些数据。 如果成功，这项研究将产生强大而有效的计算框架和相关软件，可以纠正数据以解决薄的地下地层。 分辨率和可靠性的提高将理想地允许岩土工程师识别以前无法识别的地下薄层。 这将是一个重大的方法上的进步，使研究的基本作用，薄层液化。 这项研究的结果将直接关系到该行业的利益，而该行业对研究结果的采用将通过参与弗吉尼亚理工大学岩土研究与实践中心的合作PI来加速。 这个跨学科的项目将支持两个弗吉尼亚理工大学的研究生，一个在数学和土木工程。共皮河绿色已经建立了一个退伍军人推广计划，并迄今已招募三名退伍军人在他的研究小组。 PI和CoPI将利用这个项目来进一步与退伍军人合作。在2010-2011年新西兰坎特伯雷地震序列（CES）期间，对由桑迪与粉土和粘土层互层组成的场地的地表液化表现的预测与观测严重程度进行了比较，突出了当前使用的液化评价程序的重大局限性。 一个潜在的问题是CPT识别和正确表征影响整个剖面液化响应的薄层的局限性。 多层互层对测得的CPT尖端阻力和套管摩擦力具有“平滑”效应，导致显著低估砂层的密度和高估细粒层的刚度。 虽然已经建议了针对“薄层效应”校正CPT尖端电阻的程序，但是这些程序中的大多数是手动的并且不适用于多个薄层效应。 最近开发了一种程序，通过将其作为逆问题来解释多个薄层效应，假设测量的CPT数据等于遵循简单的1D模型与深度相关空间滤波器卷积的“真实”CPT数据（Boulanger和DeJong，2018），但我们的分析表明，该程序无法在感兴趣的尺度上校正薄层（例如，几厘米或更薄的层），并且如果完全实现收敛，则通常收敛缓慢。 此外，更重要的是，当应用到一个大型数据库的液化案例的历史，从CES，该程序的产量，在整体上，不太准确的预测比如果没有薄层校正应用到CPT探测。 本项目的目标是探索一种跨学科的方法来解决这一关键问题，在评估具有挑战性的土壤场地（即，具有多个非粘性土壤薄层夹层的砂土剖面）。 将开发一种稳健的、计算上可扩展的技术来反演“真实”的静力触探（CPT）测深数据（即，校正多个薄层效应），这是基于总变分（TV）最小化方法。 为了评估开发的反演算法的有效性，材料点法（MPM）将用于模拟CPT在具有一系列感兴趣的特性的具有挑战性的土壤剖面中进行; MPM模型将首先根据校准室测试数据进行验证。 这将使我们了解双方的？真的吗？然后呢？衡量？多夹层剖面的CPT探测数据。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Robust Identification and Characterization of Thin Soil Layers in Cone Penetration Data by Piecewise Layer Optimization

通过分段层优化对锥入度数据中的薄土层进行鲁棒识别和表征

• 发表时间: 2022
• 期刊: Computers and geotechnics
• 影响因子: 5.3
• 作者: Cooper, J.

Bench-Scale Testing of Grouts for Geo-Slice Peels

地质切片剥离灌浆的实验室规模测试

• DOI: 10.1061/9780784483428.033
• 发表时间: 2021
• 期刊: Proc. International Foundations Congress and Equipment Exposition (IFCEE 2021
• 作者: Yost, K.M.

Recommended b-Value for Computing Number of Equivalent Stress Cycles and Magnitude Scaling Factors for Simplified Liquefaction Triggering Evaluation Procedures

用于计算简化液化触发评估程序的等效应力循环数和幅度比例因子的推荐 b 值

• DOI: 10.1061/(asce)gt.1943-5606.0002926
• 发表时间: 2022
• 期刊: Journal of Geotechnical and Geoenvironmental Engineering
• 影响因子: 3.9
• 作者: Ulmer, K. J.;Green, R. A.;Rodriguez-Marek, A.
• 通讯作者: Rodriguez-Marek, A.

Numerical modelling of rammed aggregate piers (RAP) in liquefiable soil

液化土中夯实骨料桥墩 (RAP) 的数值模拟

• DOI: 10.1016/j.soildyn.2021.107088
• 发表时间: 2022
• 期刊: Soil Dynamics and Earthquake Engineering
• 影响因子: 4
• 作者: Thum, T.S.;Yerro, A.;Saade, A.;Ye, E.;Wissmann, K.J.;Green, R.A.
• 通讯作者: Green, R.A.

Assessment of the efficacies of correction procedures for multiple thin layer effects on Cone Penetration Tests

锥入度试验中多个薄层效应校正程序的有效性评估

• DOI: 10.1016/j.soildyn.2021.106677
• 发表时间: 2021
• 期刊: Soil Dynamics and Earthquake Engineering
• 影响因子: 4
• 作者: Yost, Kaleigh M.;Green, Russell A.;Upadhyaya, Sneha;Maurer, Brett W.;Yerro-Colom, Alba;Martin, Eileen R.;Cooper, Jon
• 通讯作者: Cooper, Jon