SGER: Development and Verification of In-Flight Grouted Helical Pier Placement Technique for Use in Foundation Rehabilitation Investigations

摘要在过去的10年里，美国人对地基改善和地基加固(GIGR)技术的使用出现了爆炸性的增长。尽管被广泛采用，但对这类技术的分析仍然不标准化，特别是当多个GIGR系统同时使用或与现有挡土墙和基础一起使用时。随着美国城市的老龄化，对现有岩土设施的修复将进一步普及这些技术的使用。尽管越来越受欢迎，但还没有一种准确、稳健的方法来设计这类系统。开发这种设计方法的关键是理解潜在的载荷传递机制，并通过实验进行支持。这类研究有助于证实新出现的实地使用方法的适用性，同时为模式评估提供一个数据库。为此，在这个项目中，我们的研究集中在以下情况下的城市地区群桩修复问题：(1)场地条件或地质条件排除了转换梁的使用，(2)现有桩的拆除可能会破坏附近建筑物的稳定，或(3)通过建筑再利用来促进可持续性。我们的重点是开发必要的离心机工具，以支持必要的实验研究，这将加强我们对这些康复系统的负荷转移机制的了解。具体地说，该项目将为加州大学戴维斯分校的NEES离心机设施开发螺旋桥墩放置和空中灌浆技术和工具。这些技术和工具不仅对地基改善和修复有用，而且对更广泛类别的地基改善研究也是有用的。工作计划有三个主要目标：(I)开发适当的空中灌浆工具和技术，以模拟改进的基础系统；(Ii)进行一系列离心机，以验证灌浆方法的能力，并将其用于提高一个群桩基础的承载能力；以及(Iii)使急需的国际研究人员能够在(I)和(Ii)期间从以前和正在进行的研究中受益，并合作传播研究成果。飞行中的灌浆将使用固定灌浆站(站点放置在1-g，灌浆部署在N-g)，或机器人控制的灌浆放置，或两者的组合进行探索。通过NEES项目建造的新机械臂使后者成为一种可行的爆炸替代技术。拟议工作在技术贡献方面的影响，如果这项工作成功，这项工作将为更广泛的土工离心机用户群体应用空中灌浆技术提供基础，大大扩展物理模型试验的能力。此外，所调查的基础修复解决方案以及一系列离心机实验的完成将有助于证实其使用情况，并为随后的测试需求提供指导。独特的国际合作，以及对欧洲倡议(RUFUS)的参与，进一步加强了这项工作的更广泛范围。最后，这项建议涉及一个初级研究人员小组(其中两名是女性)，致力于招募不同群体的研究型学生参与这一项目。

Abstract American usage of ground improvement and ground reinforcement (GIGR) techniques has exploded in popularity over the past 10 years. Despite widespread adoption, analysis of such techniques remains non-standardized, especially when multiple GIGR systems are used concurrently or in conjunction with existing retaining walls and foundations. As American cities age, rehabilitation of existing geotechnical installations will further popularize usage of these techniques. Despite this growing popularity, an accurate, robust method for design of such systems does not exist. Key to the development of such design methods is the understanding of underlying load transfer mechanisms, supported by experimental efforts. Such studies help substantiate the applicability of new emerging field-employed methods while providing a database for model evaluation. To this end, in this project, we focus our study on the issue of rehabilitation of pile groups in urban areas when either (1) site conditions or geology preclude transfer beams usage, (2) the removal of existing piles may destabilize nearby structures, or (3) where sustainability is being promoted through building reuse. Our emphasis is on developing the necessary centrifuge tools to support the needed experimental investigations, which will enhance our understanding of the mechanisms of load transfer of these rehabilitation systems. Specifically, this project will develop helical pier placement and in-flight grouting techniques and tools for the University of California, Davis NEES centrifuge facility. Such techniques and tools will be useful not only for foundation improvement and rehabilitation, but also for the broader category of ground improvement studies. The work plan has three primary objectives: (i) develop suitable in-flight grout placement tools and techniques to simulate the improved foundation systems, (ii) conduct one centrifuge series to verify the capability of the grouting method and employ it for load capacity enhancement of one pile group foundation, and (iii) enable much needed links with international researchers to benefit from previous and ongoing research during (i) and (ii) and collaboratively disseminate findings. In-flight grout placement will be explored using either fixed grout stations (stations placed at one-g, with grout deployed at N-g), or robot-controlled placement of grout or a combination of both. The new robot arm being constructed through the NEES project makes the later technique a plausible alternative to explore.BROADER IMPACTS OF THE PROPOSED WORKIn terms of technical contribution, if successful, this work will provide the foundation for the broader geotechnical centrifuge user community to apply in-flight grouting techniques, greatly expanding the capabilities of physical model testing. Further, the foundation rehabilitation solution investigated, and the completion of one series of centrifuge experiments will help substantiate its use, and provide guidance for subsequent testing needs. The unique international collaboration, as well as involvement with European initiatives (RUFUS), further strengthens the broader reach of this work. Finally, this proposal involves a team of junior level researchers (two of whom are female), with a dedication towards recruiting a diverse population of research students, for involvement in this project.