CAREER: A Framework for Integrated Computational and Physical Simulation of Dynamic Soil-Pile Interaction

这个教师早期职业发展（Career）项目的目标是开发一个综合的研究和教育项目，旨在提高桩群动态桩-土相互作用的基础知识。为此，将在准弹性动力学和非线性范围内进行全面的综合物理和计算研究。在PI最近的NEES有效载荷项目中，为单桩开发的物理模拟方法的进展将扩展到群桩。具体而言，将使用宽带激励和随机振动信号处理技术的竖向-水平耦合摇摆试验来有效地表征土-桩-群相互作用在频域的动力响应。同时，在PI先前的离心机研究中为单桩开发的三维非均匀扰动区计算模型将扩展到更复杂和实际意义重大，但尚未得到充分理解的桩群情况。理论桩响应的敏感性将通过模型参数的参数化研究来确定，这些参数包括：(1)桩周围扰动区的模量和阻尼曲线，(2)远场的模量和阻尼曲线，(3)扰动区的大小和形状，(4)桩土接触条件。在描述它们对整体弹性动力响应的相对贡献之后，这些参数将在系统识别优化方法中被校准为观察到的实验响应，以产生观测到的土-桩-群相互作用的校准计算扰动区模型。这项研究将在使用独特的多模态和随机振动实验测试技术方面具有变革性，这些技术是在以前的离心机项目和一个全面的NEES项目中开发的；利用先进的BEM和FEM程序对动态土壤-结构相互作用（SSI）进行三维建模，这些程序具有多个、多层域的能力，通过使用扰动区连续体模型来捕获近场和远场土壤响应；并通过检验小应变的弹性动力校正扰动区模型与它们作为大应变非线性时域分析初始模型之间的联系。与CAREER计划的目的一致，该奖项将使PI能够开发一个研究计划，为整合教育和研究的终身领导奠定坚实的基础。CAREER研究项目将与一个全面的教育、推广和培训（EOT）项目统一起来，旨在加强研究生和本科生的分析和教学技能，同时向K-12学生介绍岩土工程主题。为了最大限度地发挥EOT项目的影响，这些活动将与已建立的大学外展和多元化项目进行协商，这些项目在激励K-12学生进入STEM领域以及增加未被充分代表的少数民族参与工程方面有良好的记录。EOT活动包括开发教学模块，通过国家科学基金会的TeachEngineering网站进行传播；为一年一度的科学节和K-12教室提供岩土和地震工程方面的外联讲座；国家科学基金会实地考察日，学生将通过该实地考察日了解该项目并观察测试；以及让当地中学生参与夏季研究。该项目还包括一项正式的评估计划，通过与国际滑联教育研究所的一名评估人员合作，确保EOT活动取得成功。

The goal of this Faculty Early Career Development (CAREER) Program award is to develop an integrated research and education program aimed at advancing fundamental knowledge on dynamic pile-soil interaction for pile groups. To this end, integrated full-scale physical and computational studies will be carried out in the quasi-elastodynamic and nonlinear ranges. Advancements in physical simulation methods developed for single piles in the PI's recent NEES Payload project will be extended to pile groups. Specifically, coupled vertical-horizontal-rocking tests with broadband excitation and random-vibration signal processing techniques will be used to efficiently characterize the dynamic response of soil pile-group interaction in the frequency domain. Concurrently, three-dimensional inhomogeneous disturbed-zone computational models developed for single piles in the PI's previous centrifuge studies will be extended to the more complex and practically significant, yet less well-understood, case of pile groups. The sensitivity of the theoretical pile response will be determined through parametric studies of the model parameters, including (1) modulus and damping profiles in the disturbed zones around the piles, (2) modulus and damping profiles in the far-field, (3) size and shape of the disturbed zone, and (4) pile-soil contact conditions. Upon characterizing their relative contributions to the overall elastodynamic response, these parameters will then be calibrated to the observed experimental responses in a system-identification optimization approach, to produce calibrated computational disturbed-zone models of the observed soil pile-group interaction. The research will be transformative in its use of unique multi-modal and random-vibration experimental testing techniques developed in previous centrifuge projects and a full-scale NEES project; the 3D modeling of dynamic soil-structure interaction (SSI) by advanced BEM and FEM programs with capabilities for multiple, multi-layered domains to capture both near-field and far-field soil response through the use of disturbed-zone continuum models; and by examining the link between the elastodynamically calibrated disturbed-zone models for small strains, and their performance as initial models in nonlinear time-domain analyses for large strains. In accord with the purpose of the CAREER program, this award will enable the PI to develop a research program that will build a firm foundation for a lifetime of leadership in integrating education and research. The CAREER research project will be unified with a comprehensive education, outreach and training (EOT) program aimed at strengthening the analytical and teaching skills of graduate and undergraduate students, while reaching out to K-12 students to introduce them to topics of geotechnical engineering. To maximize the impact of the EOT program, the activities will be planned in consultation with established university outreach and diversity programs with proven records of inspiring K-12 students towards STEM fields and increasing participation of underrepresented minorities in engineering. The EOT activities include development of teaching modules for dissemination via NSF's TeachEngineering web site, outreach lectures on geotechnical and earthquake engineering for an annual science festival and K-12 classrooms, NSF field days through which students will learn about the project and observe tests, and involvement of local middle school students in summer research. The project also includes a formal assessment plan to ensure the success of the EOT activities through collaboration with an evaluator from the ISU Research Institute for Studies in Education.