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

该工程研究启动（ERI）奖支持旨在了解有缺陷的埋地管道上方形成天坑的原因和方式的研究。埋管缺陷引起的天坑已成为对社区安全的重大威胁，造成人员死亡、建筑物和基础设施损坏以及经济损失。然而，地埋管道上方天坑塌陷机理尚不清楚，给天坑塌陷预测带来困难。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产生的土壤和水流条件，并建立模型来预测它们的生长。目前，美国有超过100万英里的管道接近其使用寿命，对社区构成天坑风险。该项目将扩大我们对此类天坑形成和坍塌机制的理解，从而提供预测能力。该研究还将通过建立一个基于课程开发和K-12夏令营的响应灵活的教育和推广计划来补充，以激励年轻学生在STEM领域接受大学教育。本项目的研究目标是在了解地埋管道的渐进形成和坍塌机制的基础上，预测由缺陷地埋管道引起的天坑。为实现这一目标，目标是：(i)通过实验室的土壤侵蚀试验，查明导致有缺陷管道周围土壤内部侵蚀的关键水文地质参数；（ii）利用天坑模拟器模拟由埋管缺陷引起的天坑随时间的渐进演变；(3)建立了基于时变土拱模型的考虑外荷载的塌方时间和塌方大小预测分析方法。本项目将测试三个假设：(1)当管道周围填充物的直径与D85（即85%细粒）之比达到与水力梯度相关的阈值时，缺陷埋管周围的内部土壤侵蚀开始发生；(2)淹没区塌陷坑呈锥形，与水平方向的夹角等于周围土体的摩擦角；3)淹没区以上的天坑将呈圆顶状，外部荷载将加剧圆顶的坍塌。该项目将使PI提高对有缺陷的埋地管道周围的天坑形成和塌陷的认识，并为他长期专注于埋地民用基础设施的安全性和可持续性奠定坚实的基础。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.