Design Of Dams Research Articles

Experimental Study on the Influence of Different Dam Body on the Sediment Interception and Discharge Capacity of the Cascade Permeable Dams

Sediment deposition is an ecological and environmental problem faced by most water bodies. In view of the poor structural stability and unrepeatable use of existing permeable structures, this paper proposes a cascade permeable dam, which consists of four dam bodies. As the composition of the dam material is the key to sediment interception and discharge capacity, this study sets up two groups of dam material particle sizes for experiments. The results show that the sediment interception performance of the cascade permeable dam is good. When the dam material with a small particle size is selected, the percentage of intercepted sediment mass inside the four dam bodies is 75–89%. The interception sediment rate is much greater than that of the dam material with a large particle size, which tends to decline one by one along the flow direction. The discharge capacity of the dam gradually decreases with time, and there is an obvious decrease in the permeability coefficient of 1# dam. The results of this study provide programmatic support for reducing sediment entering shallow lakes and rivers, which can further optimize the structure design of permeable dams.

The impact of hydraulic conductivity anisotropy on the effectiveness of subsurface dam

Hydraulic conductivity is a key parameter controlling groundwater flow and solute transport, and anisotropy in hydraulic conductivity is common in aquifers. Previous studies have investigated the effectiveness of subsurface dams in combating seawater intrusion (SWI) and associated environmental concerns. However, the quantitative impact of hydraulic conductivity anisotropy on the performance of subsurface dam has not been explored. This study goes beyond previous research by examining, for the first time, the effects of subsurface dams on SWI prevention in anisotropic settings. Furthermore, the study optimized subsurface dam designs in anisotropic coastal aquifers through numerical simulations that take into account the environmental impact. Our findings reveal the mechanism of hydraulic conductivity anisotropy's influence on the discharging zone and demonstrate that as the anisotropy ratio (rk) decreases, the coastal discharging zone expands landward, reducing SWI and ultimately lowering the minimum effective dam height (MEDH). This process effectively prevents SWI while maximizing fresh groundwater discharge. Increasing the rk values simultaneously expands both the MEDH and the peak fresh groundwater discharge (PFGD). Additionally, increasing the horizontal hydraulic conductivity of the aquifer significantly increases the range of PFGD, while the distance between the dam and shoreline emerges as the main factor influencing the extent of the MEDH.

Sand dam contributions to year-round water security monitored through telemetered handpump data

Sand dams are a form of rainwater harvesting, prolific in arid and semi-arid lands. Water is provided partly via handpumps, which, as the only improved method of abstraction from sand dams, are important for drinking water security. Accelerometers and cellular transmitters were fitted to 30 handpumps by the Africa Sand Dam Foundation (ASDF) in 2019 to monitor the use and reliability of the handpumps by recording hourly water volume abstracted. Data from April 2019 to October 2021 for 26 of these sites, alongside qualitative data, were analysed and each handpump’s contribution to year-round water security was explored, focusing on the long dry season when water supply from other sources is compromised. ion was over 20 times higher in the long dry season than in any other season, and at sites with higher salinity, higher livestock use, and larger dam wall area. At 21 wells, abstraction was still being recorded at the end of at least one long dry season; however, high spatial and temporal heterogeneity between pumps and seasons means that not all sand dams deliver reliable water supply year-round. Quantifying the contribution that sand dams make to water security is crucial for understanding their resilience against a changing climate and can aid decision makers when choosing the most appropriate water management technique. Knowledge of temporal and site heterogeneity in abstraction can inform when other water sources need increasing and can help with sand dam design optimisation. Overall, our results indicate the positive contribution that sand dams make to year-round water security through the water that is abstracted through handpumps.

Sensitivity analysis of factors affecting gravity dam anti-sliding stability along a foundation surface using Sobol method

The anti-sliding stability of a gravity dam along its foundation surface is a key problem in the design of gravity dams. In this study, a sensitivity analysis framework was proposed for investigating the factors affecting gravity dam anti-sliding stability along the foundation surface. According to the design specifications, the loads and factors affecting the stability of a gravity dam were comprehensively selected. Afterwards, the sensitivity of the factors was preliminarily analyzed using the Sobol method with Latin hypercube sampling. Then, the results of the sensitivity analysis were verified with those obtained using the Garson method. Finally, the effects of different sampling methods, probability distribution types of factor samples, and ranges of factor values on the analysis results were evaluated. A case study of a typical gravity dam in Yunnan Province of China showed that the dominant factors affecting the gravity dam anti-sliding stability were the anti-shear cohesion, upstream and downstream water levels, anti-shear friction coefficient, uplift pressure reduction coefficient, concrete density, and silt height. Choice of sampling methods showed no significant effect, but the probability distribution type and the range of factor values greatly affected the analysis results. Therefore, these two elements should be sufficiently considered to improve the reliability of the dam anti-sliding stability analysis.

A scaling law for the length of granular jumps down smooth inclines

Granular jumps commonly develop during granular flows over complex topographies or when hitting retaining structures. While this process has been well-studied for hydraulic flows, in granular flows such jumps remain to be fully explored, given the role of interparticle friction. Predicting the length of granular jumps is a challenging question, relevant to the design of protection dams against avalanches. In this study, we investigate the canonical case of standing jumps formed in granular flows down smooth inclines using extensive numerical simulations based on the discrete element method. We consider both two- and three-dimensional configurations and vary the chute bottom friction to account for the crucial interplay between the sliding along the smooth bottom and the shearing across the granular bulk above. By doing so, we derived a robust scaling law for the jump length that is valid over a wide range of Froude numbers and takes into account the influence of the packing density. The findings have potential implications on a number of situations encountered in industry as well as problems associated with natural hazards.

Storage Earth Dam Failure due to Liquefaction Caused by Earthquakes

Aims: We are researching causes and criteria for the liquefaction dam failure by analyzing the safety of the dam under static and dynamic loads against shear failure using the finite element technique, which is used to simulate stability assessment for selected earth dams under different loading conditions. Background: Storage Massive earth dams are vulnerable to collapse during earthquakes, which can have severe effects ranging from direct human casualties to indirect economic losses. How seismically fragile earth dams are and what issues may arise from a failure depend on how they respond to earthquakes. Slope failure, piping, displacement, and/or settlement are examples of seismic responses that are caused by weak soil and/or the liquefaction of loose sands. Earth dam failure can be caused by a variety of factors, including seepage through the dam body, hydraulic issues, structural instability, and liquefaction failure brought on by earthquakes. Objective: The objective of this study is to find a way to design of earth-fill dams. Methods: The finite element method is a numerical solution. This method is based on a grid pattern (not necessarily rectangular) which divides the flow region into discrete elements and provides N equations with N unknowns. Material properties, such as permeability, are specified for each element, and boundary conditions (heads and flow rates) are set. The finite element method has several advantages over the finite difference method for more complex seepage problems. Results: The Lower San Fernando Dam is dangerous under dynamic loads, and the F.O.S. values for the upstream and downstream directions are 0.264 and 0.183, respectively. 1350 m2 is the Lower San Fernando Dam's liquefaction area. 40.67% of the Lower San Fernando Dam's overall foundation area is represented by that figure. Tapar (India) dam is hazardous due to slope failure under dynamic loads, and the F.O.S. values for the upstream and downstream directions are 0.5 and 0.109, respectively. Tapar Dam in India has a liquefaction area of 457 m2. This amount equals 52.33 percent of the Tapar (India) dam's entire foundation area. The slope failure under dynamic loads and the F.O.S. values of 0.313 and 0.548 for the slopes of the river upstream and downstream of Fatehgadh dam (India), respectively, lead to the conclusion that it is dangerous. 333.5 m2 is the size of the liquefaction area of the Fatehgadh dam in India. The foundation area of the Fatehgadh (India) dam as a whole is represented by that figure at 78.75%. Saluda Dam in Columbia is an unsafe slope failure under dynamic loads, and the F.O.S. values for the upstream and downstream directions are 0.102 and 0.101. Saluda Dam in Columbia has a 32095 m2 liquefaction area. This value represents 32.96% of the Saluda Dam's total foundation area (Columbia). Conclusion: Conclusions state that 32.96% of the minimum liquefaction zone area is what causes liquefaction failure. Under the effect of seismic stresses, a safe design standard for storage earth dams is produced. The evaluation must also take into account the specifications for safety limitations based on global norms, regulations, and codes. examining the dam safety requirements for dynamic loads.

Hydro-mechanical simulations aid demand-oriented design of slit dams for controlling debris flows, debris avalanches and rock avalanches

Slit dams are widely used for managing multiphase geophysical flows with diverse objectives. However, quantitatively linking dam configurations and flow properties to design indices remains particularly challenging for multiphase flows. This study performs systematic hydro-mechanical simulations of slit dams in arresting debris flows, debris avalanches, and rock avalanches, using a coupled computational fluid dynamics and discrete element method (CFD-DEM). Our high-fidelity simulations reasonably capture essential physics observed in experiments. Furthermore, unified design diagrams are compiled from multiple perspectives to quantitatively link flow properties (fluid contents and Fr conditions) and spillway width to crucial design indices, including overspilling dynamics, downstream momentum reduction ratio ζ, and retention efficiency. The results reveal that: i) Fr exhibits nonlinear correlations with these design indices that vary significantly during the impact regime transitions from pile-up to runup, due to the resulting changes in the size and shape jammed and mobilized domains; ii) Both ζ and retention efficiency negatively correlate with fluid content, Fr, and spillway width, with different priorities; and iii) Fluid contents and Fr jointly govern overspilling dynamics, while increasing spillway width can effectively reduce retention efficiency by changing trap patterns, including clogging, blockage and self-cleaning traps. This study and its findings contribute deep insights into multiphase flow-dam interactions and offer a unique physics-based dataset to facilitate the demand-oriented design of slit dams for controlling various anticipated flows.

Choosing between prediction and explanation in geological engineering: lessons from psychology

ABSTRACT In their highly influential paper, Yarkoni, Tal, and Jacob Westfall. 2017. “Choosing Prediction over Explanation in Psychology: Lessons from Machine Learning.” Perspectives on Psychological Science 12 (6):1100–1122. https://doi.org/10.1177/1745691617693393 the authors highlight difficulties in traditional explanatory research in the field of psychology and argue in favour of novel data-driven science. By applying machine-learning methods to large data sets, predictive power has been shown to increase significantly. Geological engineers are responsible for a wide range of applications, including the design of tunnels, dams, foundations, and mines. While the field of geological engineering stands on solid mechanistic grounds, we argue that its predictive aspect aligns more closely with psychology than other mechanistic sciences. We therefore propose a paradigm shift in geological engineering research towards a prediction-centric approach. Potentially, this could enhance cost-effectiveness in structural design and lead to substantial societal savings.

A collaborative numerical simulation-soft computing approach for earth dams first impoundment modeling

Uncertainty quantification plays a crucial role in the design, monitoring, and risk assessment of earth dams. To reduce the computational burden, we employ a combination of finite difference method and soft computing techniques to investigate material uncertainties in earth dams during the initial impoundment stage. The findings of sensitivity analysis with the Tornado diagram indicate that key material properties such as dry density, elasticity modulus, friction angle, and Poisson’s ratio significantly influence the displacements and stress analysis. In our study, we explore four variants of extreme learning machines (ELMs): the standalone ELM, hybridized versions with the improved grey wolf optimizer algorithm, ant colony optimization for continuous domains, and artificial bee colony. These methods are assessed across various training sizes to predict multiple parameters, including horizontal and vertical displacements, stresses, and the factor of safety (FoS). The hybridized ELM with the improved grey wolf optimizer algorithm emerges as the superior choice for most of the response variables. A minimum of 200 numerical simulations is required to establish a stable and accurate meta-model with an average prediction error of less than 3% for responses and the FoS.

Dynamic Responses of Concrete-Face Rockfill Dam to Different Site Conditions under Near-Fault Earthquake Excitation

The western region of China is rich in hydropower resources and characterized by unique geological conditions. For the construction or planned construction of high dams in this region, different types of cover layers are formed due to special geological structures, most of which are located in high seismic intensity zones. This study focuses on four different site conditions: hard ground, medium–hard ground, medium–soft ground, and weak ground. By simulating the dynamic response of concrete-face rockfill dams under near-fault earthquake excitation, the vertical settlement of the dam and the attenuation of seismic motion under different site conditions are analyzed. The research findings reveal a consistent trend where the vertical settlement of the dams progressively escalates with increasing dam height across all four site conditions. This settlement phenomenon is especially pronounced in weak ground conditions, posing a potential risk of failure. Furthermore, when subjected to near-fault pulse-type earthquake motions, the existence of weak soil layers significantly dampens the seismic forces experienced by the dam. This finding suggests that the weaker the geological conditions of the site, the more pronounced the attenuation effect of the seismic motion. Additionally, the overburden layers have a noticeable amplification effect on near-fault pulse-type earthquake motion. However, this amplification effect is not significant in weak ground, possibly due to the presence of weak soil layers restricting the propagation and amplification of seismic motion. In conclusion, these research findings have practical significance for the dynamic response of high dam construction in different site conditions in the western region of China. They provide a scientific basis for the design and construction of high dams and serve as a reference for the implementation of seismic mitigation measures and earthquake disaster prevention in engineering projects.

ICOLD 2023, Gothenburg, Sweden: update on Technical Committee B

This briefing note summarises the background and current progress of ICOLD (International Commission on Large Dams) Technical Committee B, which covers seismic aspects of dam design. It summarises the ICOLD Technical Bulletins, which are currently being drafted and the activities of the technical committee during the 2023 ICOLD annual meeting.

QUANTIFYING RISKS FOR COASTAL LEVEE DESIGNS ALONG THE U.S. GULF COAST

For all U.S. Army Corps of Engineers (USACE) dam and levee designs for new projects, modifications, improvements, rehabilitation, or repairs, a risk-informed design approach is taken (ECB 2019-15). Risk-informed design ensures that risks and uncertainties are evaluated and estimated to be tolerable. This approach occurs in parallel to the typical design approach, which primarily focuses on ensuring the project is commensurate with available policies, guidance, and criteria as specified in USACE publications (regulations, manuals, etc.) as well as project-specific criteria. These criteria result in designs that achieve adequate factors of safety for levees, floodwalls, or other structural features across a full range of hydraulic, seismic, and other types of hazards. The risk-informed design approach allows for adaptability to identify cases where a lesser factor of safety may still result in tolerable risks, or conversely, where proposed criteria may not be sufficient to reduce risks to an acceptable level. These type of assessments are performed while ensuring that the project holds life safety paramount, and the design and risk teams are open and transparent in their engagement with local partners.

Characteristics of energy evolution and acoustic emission response of concrete under the action of acidic drying-saturation processes cycle

The continuous fluctuation in the acidic mine water level of the underground reservoir will affect the artificial dam's strength and stability. The uniaxial compression test of C25 concrete under different drying-saturation processes cycle (DSPC) numbers and pH solutions were performed. The degradation mechanism of mechanical properties of concrete under acidic DSPC was investigated; the calculation formula for the elastic strain energy at peak stress has been corrected and the energy evolution law has been obtained; besides, the evolution characteristics of acoustic emission (AE) parameters were studied using multi-fractal theory and the precursor characteristics of concrete failure were obtained. The results revealed that increasing the DSPC times or decreasing the pH caused an increase in the saturation moisture content of the concrete, the strain and elastic strain energy of the concrete at peak stress increased, a drop in the ultrasonic velocity, the uniaxial compressive strength (UCS), the elastic modulus (EM) and the overall input energy. The accumulated ringing count and accumulated energy of AE dramatically increased before the concrete was close to failure, and numerous low-frequency and high-amplitude signals started to appear. The information mentioned above might be considered a short-impending warning of concrete failure. During the plastic deformation, the large increase of the multi-fractal parameter Δα and the significant drop of Δf might be viewed as early warning for concrete failure. This research will offer some theoretical direction for artificial dam design and long-term stability monitoring in underground reservoirs.

Experimental and DEM-CFD Coupling Investigations on the Characteristics and Mechanism of Seepage Erosion for Cohesionless Soil

Seepage erosion is one of the main reasons for the local collapse or instability of embankments. To investigate the characteristics and mechanism of seepage erosion for cohesionless soils, model tests using an independently developed seepage erosion device and numerical simulations based on a discrete element method-computational fluid dynamics (DEM-CFD) coupling model were carried out. The results show that the seepage erosion process of cohesionless soil could be characterized by four stages: stable seepage, upward migration of fine particles, boiling of sand samples, and erosion damage. The skeleton structure of a soil sample under seepage flow was continually changed due to the loss of fine soil particles, which resulted in a significant decrease in the sample strength and could, ultimately, lead to the failure of the sample. The results of this study can provide references and bases for the design, construction, and long-term service of embankments or earth dams under complex seepage conditions, reducing the risk of seepage erosion.

Peatland gully restoration with stone and timber dams (Kinder Plateau, UK)

Blanket peat erosion is widespread in the British Isles. Eroded gullies have formed largely from the action of running water, with anthropogenic influences thought to have initiated and accelerated erosion. Currently, many blanket peatlands are undergoing restoration using aerial applications of lime, seed, fertiliser, and hand spreading of heather mulch (LSFM) on bare peat flats and blocking gullies with dams. Dams help stabilise areas of bare peat, trap sediment, reduce runoff velocities, raise water tables, and promote the re-vegetation of peat-forming plant species. Few studies have examined how gully blocks change over time and what this means for the functions they provide. We randomly sampled 500 of >2500 small stone and timber dams 8–9 years after installation in an eroding blanket peatland. We measured: vegetation cover and abundance, sediment accumulation behind dams, and available water storage capacity in dam pools as determined by gully morphology. On average, 92% and 93% of gully floors and 85% and 95% of gully walls were fully vegetated, while mean sediment depths were 22 and 20 cm, representing 42% and 44% infill for stone and timber dams, respectively. 2% of dams had failed, suggesting that failure is rare within the first decade. Most retained upstream pools, filling 18% (stone) and 44% (timber) of remaining storage. Sediment accumulation depths (and, conversely, available storage) did not differ significantly between stone and timber dams (95% CI) nor with distance down the gully. Results showed broadly consistent storage depth behind blocks independent of gully properties or dam design. These results suggest that sedimentation depths behind dams quickly reach equilibrium with subsequent sediment inputs balanced by the flux over the dam. Runoff attenuation functions from gully blocking were maintained for almost a decade. Therefore, re-vegetated gully blocked systems likely represent a stable equilibrium condition for the restored peatland so that the restored functions are a long-term benefit of peatland restoration.

The Use of Shape Accel Array for Deformation Monitoring and Parameter Inversion of a 300 m Ultrahigh Rockfill Dam

The global construction of rockfill dams has now surpassed the 300 m height level. Despite great achievements in dam design and construction, monitoring techniques have lagged behind the development of high rockfill dams. Existing deformation monitoring techniques are ill-suited to the high earth and water pressures, and extended monitoring periods are required for ultrahigh rockfill dams. This study introduces, for the first time, the use of a shape accel array (SAA) to monitor internal displacement in a 300 m high earth core rockfill dam. The SAA employs a rope-like array of capacitive MEMS accelerometers for deformation measurement. Compared to conventional monitoring techniques, SAA is a data-intensive monitoring technique. Based on the intensive data obtained from SAA, we employed a parameter inversion method, utilizing multiobjective optimization algorithm, the nondominated sorting genetic algorithm-III (NSGA-III), to inverse the constitutive model parameters of the rockfill dam. The multiobjective parameter inversion method maximizes the use of multisource monitoring data for predicting rockfill dam deformation.

Deep-Learning-Enhanced CT Image Analysis for Predicting Hydraulic Conductivity of Coarse-Grained Soils

Permeability characteristics in coarse-grained soil is pivotal for enhancing the understanding of its seepage behavior and effectively managing it, directly impacting the design, construction, and operational safety of embankment dams. Furthermore, these insights bridge diverse disciplines, including hydrogeology, civil engineering, and environmental science, broadening their application and relevance. In this novel research, we leverage a Convolutional Neural Network (CNN) model to achieve the accurate segmentation of coarse-grained soil CT images, surpassing traditional methods in precision and opening new avenues in soil granulometric analysis. The three-dimensional (3D) models reconstructed from the segmented images attest to the effectiveness of our CNN model, highlighting its potential for automation and precision in soil-particle analysis. Our study uncovers and validates new empirical formulae for the ideal particle size and the discount factor in coarse-grained soils. The robust linear correlation underlying these formulae deepens our understanding of soil granulometric characteristics and predicts their hydraulic behavior under varying gradients. This advancement holds immense value for soil-related engineering and hydraulic applications. Furthermore, our findings underscore the significant influence of granular composition, particularly the concentration of fine particles, on the tortuosity of water-flow paths and the discount factor. The practical implications extend to multiple fields, including water conservancy and geotechnical engineering. Altogether, our research represents a significant step in soil hydrodynamics research, where the CNN model’s application unveils key insights into soil granulometry and hydraulic conductivity, laying a strong foundation for future research and applications.

Effect of material particle size on the permeability characteristics and sediment retention performance of cascade permeable dam

The permeable dam is a dam constructed with gravel or other material to control the sediment in rivers or channels. Experiments were conducted to study the effects of the flow rate, sediment concentration, and dam material size D on the sediment retention and permeability characteristics of the cascade permeable dams. The results show that when the water level H1t before the first dam reaches the specified failure height, the total water volume for D = 1–2 mm is inversely proportional to the sediment concentration and basically increases as the flow rate increases. The sediment mass retained by the first dam accounts for 44–56% (D = 1–2 mm) and 26–35% (D = 3–5 mm) of the total sediment mass retained by the cascade dams, and the former mainly realizes the sediment retention through the retention of the first dam, while the latter through the material retention and sediment deposition between two adjacent dams. The average permeability coefficient k of the first dam was observed to decrease by 39–62% (D = 3–5 mm) and 46–64 (D = 1–2 mm) due to the sediment clogging. The decrease rate of k (D = 1–2 mm) or decrease amplitude of k (D = 3–5 mm) are positively correlated with the sediment concentration. Under all working conditions, H1t rises rapidly and then steadily, and the rising rate for D = 1–2 mm is proportional to the sediment concentration, and increases first and then decreases as the flow rate increases. The prediction formula of H1t is proposed based on the experimental data. The research results are of reference value for the design and study of permeable dams in the future.

Objectivity and Intellectual Humility in Scientific Research: They’re Harder Than You Think

We begin from the assumption that where scientific research will predictably be used to affect things of moral significance in the world, you have a special duty, a duty of care, to ‘get it right’. This, we argue, requires a special kind of objectivity, ‘objectivity to be found’. What is it that’s to be found? In any kind of scientific endeavour, you should make all reasonable efforts to find the right methods to get the right results to serve the purposes at stake and neither exaggerate nor underestimate the credibility of what you have done. That, we take it, is what in this context constitutes objectivity and intellectual humility. But where your results will affect the world, you have a more demanding duty: a duty to ‘get it right’ about the purposes the endeavour should serve. Often the most morally significant purposes are those that ‘go without saying’ and because they are not said, we can too easily overlook them, sometimes at the cost even of human lives. We illustrate this with the example of the Vajont dam design and the flawed modelling that resulted in the Hillsborough football disaster.

Strategic siting and design of dams minimizes impacts on seasonal floodplain inundation

Dams and reservoirs aid economic development but also create significant negative impacts. Dams fragment rivers and reduce longitudinal connectivity on a network scale. However, dams may also alter discharge regimes and flood peaks, consequently reducing floodplain inundation and lateral channel floodplain connectivity, which impacts floodplain associated ecosystems. Strategic planning has emerged as a promising approach to find a balance between dam impacts and benefits. Yet, strategic planning has predominantly focused on longitudinal connectivity due to the difficulty of including the complex interactions between dam design and operations, hydrologic regime alteration, and the hydrodynamic processes controlling downstream flood extent. Here, we present how to reduce conflicts between hydropower development and loss of floodplain inundation extent by jointly optimizing siting and design of many dams in a data scarce basin. We deploy a coupled hydrological—hydraulic simulation model linked to a multiobjective optimization framework to find development options with the least trade-offs between power generation and downstream impacts on floodplains. Our results for the Pungwe Basin in Mozambique indicate that whilst portfolios of many small storage and run-of-river diversion hydropower plants might create less impacts on the downstream floodplains, installation of some large storage dams would be necessary to attain higher levels of hydropower generation.