ERI: Progressive Formation and Collapse Mechanisms of Sinkholes Caused by Defective Buried Pipes

该工程研究启动奖(ERI)支持旨在了解有缺陷的地下管道上方为什么以及如何形成天坑的研究。有缺陷的地下管道造成的天坑已成为对社区安全的重大威胁，造成人员伤亡、建筑物和基础设施损坏和经济损失。然而，地下管道上方天坑的坍塌机理尚不清楚，这使得预测天坑坍塌变得困难。在这个项目中，研究小组将确定缺陷管道周围最容易导致天坑形成的土壤和水的流动条件，并开发模型来预测它们的生长。目前，美国有100多万英里长的管道即将使用寿命结束，这对他们的社区构成了天坑风险。这个项目将扩大我们对这种天坑的形成和坍塌机制的理解，以提供预测能力。这项研究还将通过建立基于课程开发和K-12夏令营的响应和灵活的教育和外展计划来补充，该计划可以激励年轻学生在STEM领域继续他们的大学教育。该项目的研究目标是基于对逐渐形成和坍塌机制的了解来预测由有缺陷的埋地管道造成的天坑。为了实现这一目标，目标是：(I)通过实验室土壤侵蚀试验，确定导致缺陷管道周围土壤内部侵蚀的关键水文地质参数；(Ii)使用天坑模拟器模拟地下管道缺陷导致的天坑随时间的演变；以及(Iii)基于随时间变化的土壤拱化模型，开发一种考虑外部荷载的分析方法，以预测天坑的坍塌时间和大小。本项目将检验三个假设：(1)当管道周围土壤填充的孔径与D85(即85%细粉)的比率达到与水力坡度相关的阈值时，缺陷埋地管道周围的内部土壤侵蚀就会开始；(2)淹没区域中的天坑呈圆锥形，与周围土壤的水平方向夹角等于周围土壤的摩擦角；以及(3)淹没区域上方的天坑将呈穹顶状，拱顶在外部荷载下会被夸大坍塌。该项目将使PI提高对有缺陷的地下管道周围的天坑形成和坍塌的了解，并为他专注于埋藏的民用基础设施的安全和可持续性的长期职业生涯奠定坚实的基础。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This Engineering Research Initiation (ERI) award supports research that aims to understand why and how sinkholes form above defective buried pipes. Sinkholes induced by defective buried pipes have become a substantial threat to community safety, resulting in fatalities, damage to buildings and infrastructure, and economic loss. However, the collapse mechanism of sinkholes above buried pipes remains unclear, making prediction of sinkhole collapses difficult. In this project, the research team will identify the most susceptible soil and water flow conditions around defective pipes leading to sinkhole initiation and develop models to predict their growth. Currently, the US has more than one million miles of pipes nearing the end of their service lives that pose a sinkhole risk to their communities. This project will expand our understanding of formation and collapse mechanisms of such sinkholes to provide predictive capabilities. The research will also be complemented by establishing a responsive and flexible educational and outreach program based on curriculum development and K-12 summer camps that can motivate young students to pursue their college education in STEM fields.The research goal of this project is to predict sinkholes caused by defective buried pipes based on understanding of progressive formation and collapse mechanisms. To achieve this goal, the objectives are to (i) identify critical hydrogeological parameters leading to initiation of soil internal erosion around defective pipes through soil erosion tests in the laboratory; (ii) model the time-dependent progressive evolution of sinkholes induced by defective buried pipes using a sinkhole simulator; and (iii) develop an analytical method to predict the collapse timing and size of sinkholes considering external loads based on time-dependent soil arching models. This project will test three hypotheses: (1) internal soil erosion around defective buried pipes initiates when the ratio of hole diameter to D85 (i.e., 85% percent fines) of soil infill surrounding the pipe reaches a threshold value related to the hydraulic gradient; (2) sinkholes in a submerged zone will be cone-shaped with an angle from the horizontal direction that equals to the surrounding soil friction angle; and 3) sinkholes above the submerged zone will be dome-shaped, and collapse of the dome will be exaggerated by external loads. This project will allow the PI to advance knowledge of the sinkhole formation and collapse around defective buried pipes and to lay a firm foundation for his long-term career focused on safety and sustainability of buried civil infrastructures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.