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

该学院早期职业发展(Career)计划奖的目标是开发一个综合研究和教育计划，旨在促进群桩动态桩土相互作用的基础知识的发展。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步将扩展到群桩。具体而言，将采用宽带激励和随机振动信号处理技术相结合的竖向-水平-摇摆耦合试验技术，在频域内有效地表征土桩-群桩相互作用的动力响应。同时，在PI以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、具有实际意义但不太被理解的群桩情况。通过对模型参数的参数研究来确定理论桩响应的灵敏度，这些参数包括：(1)桩周围扰动区的弹性模量和阻尼线；(2)远场的弹性模量线和阻尼线；(3)扰动区的大小和形状；(4)桩土接触条件。在确定了它们对整体弹性动力响应的相对贡献后，这些参数将在系统识别优化方法中被校准到观测的试验响应，以产生观测到的土桩-群桩相互作用的校准计算扰动区模型。这项研究将在以下方面产生革命性的影响：使用在以前的离心机项目和全尺寸NEES项目中开发的独特的多模式和随机振动试验测试技术；通过先进的边界元和有限元程序对动态土-结构相互作用(SSI)进行三维建模，该程序具有通过使用扰动区连续模型来捕获近场和远场土壤响应的能力；以及通过检查小应变的弹性动力学校准扰动区模型与它们在大应变非线性时域分析中作为初始模型的性能之间的联系。根据职业计划的目的，这一奖项将使PI能够开发一个研究计划，为终身领导教育和研究的整合奠定坚实的基础。职业研究项目将与旨在加强研究生和本科生的分析和教学技能的综合教育、推广和培训(EOT)计划相统一，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计划的影响，这些活动将与现有的大学外展和多样化计划进行协商，这些计划具有激励K-12学生走向STEM领域的证明记录，并增加代表不足的少数族裔对工程学的参与。EOT活动包括开发通过NSF的TeachEngineering网站传播的教学模块、为一年一度的科学节和K-12课堂举办的岩土工程和地震工程外展讲座、NSF学生将通过其了解项目和观察测试的实地考察日，以及让当地中学生参与暑期研究。该项目还包括一项正式评估计划，通过与执行支助股教育研究所的一名评估员合作，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.