Optimizing Seismic Resilience in Historical Hydraulic Structures: Evaluating the Role of Micropiles in the Rehabilitation of the Zefta Barrage

Abstract The seismic strengthening of historical water structures is crucial to preserve their stability and functionality during earthquakes, preventing catastrophic failures and ensuring the safety of surrounding communities. This paper focuses on the Zefta Barrage in Egypt, a historical structure constructed in 1902 and still in operation today, presenting a comprehensive case study on seismic rehabilitation. Based on extensive field investigation and rehabilitation processes, numerical simulations are conducted to assess the structural response of the barrage under three earthquake response spectrums with return periods of 100, 300, and 475 years. A finite-element model incorporating soil–pile–structure interaction is developed to accurately capture the dynamic behavior of the barrage. The proposed rehabilitation measures involved the installation of vertical and inclined micropiles within the piers, and a parametric study was conducted to determine the optimal allocation and diameter of these micropiles. The analysis highlights the variations in the barrage period, displacement, and internal forces across the different earthquake scenarios. The findings reveal that, without rehabilitation, the structure is vulnerable to localized failure, particularly at critical points such as the toes of the piers, where maximum principal stresses and shear forces significantly increase with seismic intensity. Although the introduction of vertical and inclined micropiles provides additional support, their effectiveness in reducing stresses and shear forces is limited, showing minimal improvement compared to the unreinforced condition. The findings underscore the importance of incorporating soil–pile–structure interaction in predicting the seismic response accurately. The study highlights the potential of pier reinforcement with micropiles to mitigate seismic risks, offering valuable insights for the seismic design and retrofitting similar hydraulic structures in seismically active regions.