Earthen dams are indispensable infrastructure components, playing a pivotal role in flood management, drinking water supply, agricultural irrigation, and energy production. These structures are critical for sustainable water resource management, particularly in regions prone to water scarcity or flooding, such as East Azerbaijan, Iran. The design and construction of earthen dams require meticulous attention to detail to ensure their long-term stability and safety. Among the most critical design considerations is the placement of the impermeable core, which serves as a barrier to control seepage, distribute internal pressures, and maintain structural integrity. Improper core placement can lead to excessive seepage, increased hydraulic gradients, and elevated uplift forces, all of which pose significant risks to the dam’s stability and the safety of downstream communities. This study, based on real-world data from an earthen dam in East Azerbaijan, investigates the impact of core position on two key performance metrics: hydraulic gradient and uplift force. By employing advanced numerical modeling techniques, the study provides actionable insights for optimizing earthen dam design, enhancing safety, and reducing the risk of structural failure.

The primary objective of this study was to evaluate how different positions of the impermeable core affect the hydraulic and structural performance of an earthen dam. The impermeable core, typically constructed from materials such as clay with low permeability, is designed to minimize water seepage through the dam body. Seepage, if uncontrolled, can lead to internal erosion (piping), increased pore water pressure, and potential dam failure. Additionally, the core’s position influences the distribution of hydraulic pressures and uplift forces, which can destabilize the dam if not properly managed. The study focused on three core configurations—central, upstream inclined, and downstream inclined—to determine which position offers the best balance of seepage control, pressure distribution, and structural stability. The research was conducted using data from an operational earthen dam in East Azerbaijan, a region characterized by diverse hydrological and geotechnical conditions. This context underscores the importance of tailoring dam designs to local conditions while adhering to universal engineering principles.

Numerical modeling was employed to simulate the behavior of the earthen dam under different core configurations. The study utilized the Seep/W module of GeoStudio, a widely recognized software for geotechnical and hydraulic analysis. The finite element method (FEM) was used to model seepage flow and pressure distribution within the dam. FEM is particularly suited for this purpose, as it allows for detailed simulation of complex geometries and material properties, capturing the intricate interactions between water flow and soil mechanics. The dam model was constructed based on real-world data, including soil properties, dam geometry, and hydrological conditions specific to the East Azerbaijan site. The material properties, such as permeability, porosity, and shear strength, were kept consistent across all models to isolate the effect of core position.

Three core configurations were modeled: central, positioned at the midpoint of the dam’s cross-section, ensuring symmetry in pressure distribution; upstream inclined, tilted toward the upstream face, potentially reducing seepage but altering pressure gradients; and downstream inclined, tilted toward the downstream face, which may increase exposure to hydraulic pressures. Identical boundary conditions, including reservoir water levels and downstream drainage, were applied to all models to ensure a fair comparison. The models accounted for steady-state seepage under normal operating conditions, with the reservoir at full supply level. Key output parameters included the hydraulic gradient, a measure of the driving force for seepage, and uplift force, the upward pressure exerted by water on the dam’s foundation. These parameters were quantified to assess their impact on structural stability and the potential for failure mechanisms such as piping or foundation uplift.

The results of the numerical simulations revealed significant differences in the performance of the three core configurations. The central core configuration demonstrated the most favorable outcomes across all measured parameters. It reduced the hydraulic gradient by 40% compared to baseline conditions, effectively limiting seepage to a rate of 2.5 liters per second per meter of dam width. This low seepage rate is critical for preventing internal erosion, which can weaken the dam over time. Additionally, the central core facilitated a uniform distribution of pore water pressure across the dam’s cross-section. This balanced pressure distribution minimized stress concentrations, reducing the likelihood of localized failures and ensuring optimal structural stability. The uplift force in the central core model was also significantly lower than in the inclined configurations, further contributing to its stability.

In contrast, the upstream inclined core exhibited less favorable performance. The hydraulic gradient increased by 25% compared to the central core, indicating a higher driving force for seepage. This increase in gradient resulted in an uplift force of 120 kilopascals, suggesting elevated internal pressures that could compromise the dam’s stability. The higher uplift force is particularly concerning, as it indicates a potential for foundation instability, where water pressure could lift the dam base, leading to cracking or sliding. While the upstream inclined core still controlled seepage to some extent, its performance was suboptimal compared to the central core, highlighting the trade-offs associated with this configuration.

The downstream inclined core performed the least effectively, with the most significant implications for dam safety. This configuration increased the uplift force by 35% compared to the central core, reaching 150 kilopascals. The elevated uplift force is a critical concern, as it significantly increases the risk of structural damage, particularly through mechanisms such as foundation uplift or internal cracking. The downstream inclined core also exhibited higher seepage rates and hydraulic gradients than the central core, further exacerbating the potential for instability. The increased pressure concentrations in the downstream region could lead to piping, where water erodes soil particles, creating channels that weaken the dam’s structure. These findings indicate that the downstream inclined core is the least desirable configuration for ensuring long-term dam safety.

The study’s findings underscore the critical role of core placement in the design and performance of earthen dams. The central core configuration consistently outperformed the inclined alternatives, offering superior control over seepage, hydraulic gradient, and uplift forces. The 40% reduction in hydraulic gradient and the low seepage rate of 2.5 liters per second per meter highlight the central core’s ability to minimize water flow through the dam, reducing the risk of internal erosion and pressure-related failures. The uniform pressure distribution further enhances stability by preventing stress concentrations that could lead to cracking or sliding. In contrast, the upstream and downstream inclined cores introduced significant risks. The upstream inclined core’s 25% increase in hydraulic gradient and 120-kilopascal uplift force suggest a moderate risk of instability, while the downstream inclined core’s 35% increase in uplift force (150 kilopascals) poses a severe threat to structural integrity.

The implications of improper core placement are profound. Excessive seepage and uplift forces can lead to catastrophic failures, such as dam breaches, which have devastating consequences for downstream communities, infrastructure, and ecosystems. Historical examples, such as the Teton Dam failure in 1976, illustrate the dangers of poor seepage control and inadequate design. By prioritizing a central core configuration, engineers can mitigate these risks, ensuring that the dam operates safely under a wide range of hydrological conditions. The study’s findings are particularly relevant for regions like East Azerbaijan, where earthen dams are integral to water management and flood control.

This study provides practical guidance for civil engineers and dam designers, emphasizing the benefits of a centrally positioned impermeable core. This configuration minimizes seepage and hydraulic gradients while ensuring balanced internal forces, thereby enhancing dam safety and longevity. The findings are applicable not only to new dam construction but also to the retrofitting of existing structures to improve their performance. The study also sets the stage for future research, which could explore additional factors such as soil heterogeneity, varying hydraulic conditions, or long-term environmental impacts to further refine dam design practices. For instance, investigating the effects of seasonal variations in reservoir levels or the incorporation of advanced materials could provide additional insights into optimizing core performance.

The results contribute to the broader field of earthen dam engineering by offering evidence-based recommendations for improving the safety and performance of critical infrastructure. In regions like East Azerbaijan, where water resource management is a priority, the adoption of a central core design can enhance the reliability of earthen dams, ensuring their ability to withstand operational and environmental stresses. By reducing seepage, hydraulic gradients, and uplift forces, the central core configuration minimizes the risk of failure, protecting both human lives and economic assets. The study also highlights the importance of rigorous numerical modeling in dam design, as tools like GeoStudio enable engineers to simulate complex scenarios and make informed decisions.

In conclusion, this study demonstrates that the central core configuration is the optimal choice for earthen dam design, offering significant advantages in seepage control, pressure distribution, and structural stability. The upstream and downstream inclined cores, while viable in certain contexts, introduce unacceptable risks that could lead to failure under operational conditions. By adopting the central core design, engineers can enhance the safety and longevity of earthen dams, contributing to sustainable water resource management and flood control. The insights provided here are a valuable resource for dam designers, policymakers, and stakeholders involved in the planning and maintenance of critical infrastructure.