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，美国地基处理和地基加固（GIGR）技术的使用呈爆炸式增长。 尽管被广泛采用，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的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，鲁棒的方法设计这样的系统不存在。 这种设计方法的发展的关键是基本的负载传递机制的理解，实验工作的支持。 这些研究有助于证实新出现的现场使用的方法的适用性，同时提供一个数据库的模型评估。 为此，在本项目中，我们的研究重点是在城市地区的桩群修复问题，当（1）现场条件或地质排除使用转换梁，（2）拆除现有桩可能会破坏附近结构的稳定，或（3）通过建筑物再利用促进可持续发展。 我们的重点是开发必要的离心工具，以支持所需的实验研究，这将提高我们的理解这些康复系统的负荷转移的机制。具体而言，本项目将为加州大学戴维斯分校NEES离心机设施开发螺旋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良和修复有用，而且对更广泛的地基改良研究也有用。 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）进行一系列离心试验，以验证灌浆方法的能力，并将其用于提高一个桩群基础的承载能力，和（iii）与国际研究人员建立急需的联系，以便从（i）和（ii）期间以前和正在进行的研究中受益，并合作传播研究结果。 将使用固定灌浆站（灌浆站放置在1g，灌浆部署在N-g）或机器人控制灌浆放置或两者的组合来探索空中灌浆放置。 通过NEES项目建造的新机器人手臂使后一种技术成为一种可行的替代方案。拟议工作的更广泛影响就技术贡献而言，如果成功，这项工作将为更广泛的土工离心机用户社区提供应用空中灌浆技术的基础，大大扩展物理模型测试的能力。 此外，研究的地基修复方案以及一系列离心机实验的完成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，以及参与欧洲倡议（RUFUS），进一步加强了这项工作的广泛影响。 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），致力于招募各种研究生参与该项目。

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.