The effect of a defective permeable zone inside the clay core of an earthfill dam with regard to the seepage aspect
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The effect of a defective permeable zone inside the clay core of an earthfill dam with regard to the seepage aspect Hamed Farshbaf Aghajani1 · Peyman Shahbazi1 · Mohammad Salimi1 · Reza Azimzadeh1 Received: 11 June 2020 / Accepted: 17 August 2020 © Springer Nature Switzerland AG 2020
Abstract A permeable zone inside the clay core of zoned earthfill dams may prevent the infrastructure from functioning properly. This paper aims to explore the influence of a defective permeable zone inside the clay core of an earthfill dam on the seepage functioning of the dam. The seepage behavior of an earthfill dam subjected to a weakness zone with various conditions and geometries is analyzed via numerical analysis. Then, the performances of some remedial works for rehabilitating a defective dam are investigated. According to the results, the occurrence of a weakness zone with a limited area inside the core does not influence the total seepage discharge through the dam body, and in turn, the hydraulic gradient in an adjacent intact part of the clay core increases to above 5, which may enlarge the defective zone. Furthermore, if a large area of the clay core from the upstream to downstream sides of the core becomes defective, the seepage discharge through the dam body is considerably increased up to 355 times greater than the intact condition. The performance of a remedial cutoff wall for rehabilitation of the waterproofing system of the dam depends on the interaction with the adjacent clay core. This type of interaction imposes an irregular shape in a phreatic curve and changes the hydraulic head regime at the upstream of the cutoff wall axis. Additionally, around the defective zone of the clay core, the remedial cutoff wall experiences a large hydraulic gradient up to 17. Keywords Earthfill dam · Seepage analysis · Defective zone · Critical hydraulic gradient · Remedial cutoff wall
1 Introduction Today, dams play a prominent role in human civilizations of water supplying, flood control, and energy production. The clay core of zoned earthfill dams acts as the main waterproofing element of the dam. Thus, imposing any weakness in the impervious core may prevent the dam from proper functioning and even threaten the dam safety. Herein, the defect in the clay core refers to a zone inside the core where the permeability and other specifications differ from the original intact clay. This defective zone not only increases the seepage magnitude and causes unexpected deformation but also increases the internal erosion potential of the fine-grained soil of the clay core
[1]. The gradual erosion of clay particles may consequently increase the permeability in the adjacent intact part of the core and progressively enlarge the weakness zone [1–4]. Several factors may cause and develop weakness and defective zones inside the dam core. Some of the weakness reasons are related to problems raised during the construction phase. For instance, using poor-quality fine-grained materials, such as a dispersive or low-plasticity soils [5, 6], low qual
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