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

这个工程研究启动（ERI）奖支持的研究，旨在了解为什么以及如何天坑形成以上有缺陷的埋管。由有缺陷的埋地管道引起的天坑已经成为对社区安全的重大威胁，导致人员死亡、建筑物和基础设施损坏以及经济损失。然而，埋地管道上方的天坑塌陷机理尚不清楚，使得天坑塌陷预测困难。在这个项目中，研究小组将确定导致天坑形成的有缺陷管道周围最容易受到影响的土壤和水流条件，并开发模型来预测它们的增长。目前，美国有超过100万英里的管道接近其使用寿命的终点，这对他们的社区构成了天坑风险。该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。此外，还将在课程开发和K-12夏令营的基础上，建立一个响应灵活的教育和推广计划，以激励年轻学生在STEM领域继续接受大学教育。本项目的研究目标是基于对渐进形成和坍塌机制的理解，预测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开始的关键水文地质参数;（ii）使用天坑模拟器模拟由缺陷埋地管道引起的天坑随时间的渐进演变;及（iii）发展一种分析方法，以预测塌陷时间及天坑的大小，并考虑基于随时间变化的土壤沉降模型的外部荷载。本项目将检验三个假设：（1）当孔径与D85的比值（即，（2）淹没区中的天坑将呈锥形，其与水平方向的夹角等于周围土壤的摩擦角;（3）淹没区上方的天坑将呈圆顶形，外部荷载将加剧圆顶的坍塌。该项目将使PI能够进一步了解有缺陷的地下管道周围的天坑形成和坍塌，并为他专注于地下民用基础设施的安全性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.