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

在过去的10年里，美国地面改善和地面加固技术（GIGR）的使用迅速普及。尽管这些技术被广泛采用，但对这些技术的分析仍然是非标准化的，特别是当多个GIGR系统同时使用或与现有挡土墙和基础结合使用时。随着美国城市的老化，现有岩土工程设施的修复将进一步推广这些技术的使用。尽管这种日益普及，一个准确的，稳健的方法来设计这样的系统并不存在。开发这种设计方法的关键是理解潜在的载荷传递机制，并得到实验努力的支持。这些研究有助于证实新出现的实地采用方法的适用性，同时为模型评价提供了一个数据库。为此，在本项目中，我们将重点研究以下情况下城市地区桩群的修复问题：(1)场地条件或地质条件不允许使用转换梁，(2)拆除现有桩群可能会破坏附近结构的稳定，或(3)通过建筑再利用促进可持续性。我们的重点是开发必要的离心机工具来支持所需的实验研究，这将增强我们对这些康复系统负荷转移机制的理解。具体而言，该项目将为加州大学戴维斯分校NEES离心机设施开发螺旋墩安置和飞行注浆技术和工具。这些技术和工具不仅对地基改善和修复有用，而且对更广泛的地基改善研究也有用。该工作计划有三个主要目标：(i)开发合适的空中注浆放置工具和技术来模拟改进后的基础系统；（ii）进行一个离心机系列来验证注浆方法的能力，并将其用于提高一个桩群基础的承载能力；（iii）在(i)和（ii）期间与国际研究人员建立急需的联系，以便从以前和正在进行的研究中受益，并合作传播研究结果。将使用固定的灌浆站（灌浆站放置在1 -g，灌浆部署在N-g）或机器人控制的灌浆放置或两者的结合来探索飞行中的灌浆放置。通过NEES项目构建的新机械臂使后一种技术成为探索的可行选择。就技术贡献而言，如果成功，这项工作将为更广泛的岩土离心机用户社区应用飞行注浆技术提供基础，大大扩展物理模型测试的能力。此外，对基础康复液进行了研究，并完成了一系列离心机实验，将有助于证实其使用，并为后续测试需求提供指导。独特的国际合作，以及与欧洲倡议（RUFUS）的参与，进一步加强了这项工作的更广泛范围。最后，该提案涉及一个初级研究人员团队（其中两名是女性），致力于招募不同人群的研究生参与该项目。

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.