Laboratory investigation effects of control measures for leakage-induced erosion on seepage interactions in defective underground structures

Abstract

Leakage-induced erosion in underground engineering has emerged as a critical issue, leading to frequent accidents and posing significant threats to structural stability and safety. While extensive research has explored the seepage behavior of individual structures, the interactions between the defects, particularly following the implementation of preventive or remedial measures, are not fully understood. Moreover, more effective solutions are needed to address scenarios involving multiple coexisting defects. In this study, laboratory experiments were conducted to simulate seepage conditions under various scenarios, and the aim was to investigate the mechanisms of seepage erosion initiation caused by the interactions between the near-upstream (higher hydraulic head) and far-upstream (lower hydraulic head) defects. Different reinforcement methods for near-upstream defects were evaluated, and the observed grain-scale erosion mechanisms at each defect were considered. Using the same thickness of cohesive soil to cover the defects, the other methods showed failures at either or both types of defects within a differential head that was much lower than that of a new method for controlling seepage erosion. In the new method, cohesive soil was completely replaced with sandy soil at near-upstream defects, and appropriate drainage facilities were installed to enable the maintenance of the structural integrity until the near-upstream defect exceeded 160 mm and the far-upstream defect exceeded 148 mm. The findings from this study provided valuable insights into designing more efficient and comprehensive seepage management systems for underground engineering projects.