Dam Toe Research Articles

A simplified method for predicting overflow-induced crack propagation in gravity dams using genetic algorithm and material-based model

Cracks are always a serious concern in the stability analysis of gravity dams. One of the main reasons for the initiation of cracks is overflows. In evaluating dam safety under flood conditions, it is crucial to consider the balance between the strength of the dam body and the propagation of cracks. In this context, simplified equations serve as valuable tools in dam design as they offer a quick and efficient way to estimate the behavior of the dam structure. In this study, firstly using a polygonal material-based model (P-MBM), which is improved in considering the softening behavior of joints, the micro-crack propagation in masonry material is investigated. Then, based on performing 81 numerical simulations in a parametric study on the geometrical and geotechnical properties of the dam subjected to overflow, a great database of the behavior of different dams is investigated. Then, using the genetic algorithm, a set of equations is proposed, and their accuracy is validated through UDEC simulations and some theoretical methods from existing literature. For all models, the crack tends to be horizontal at the initial phase. Then, due to increasing the compressive stresses on the downstream side, the fractures tend to the dam toe. The results also indicate that the proposed equations can reasonably determine the behavior of gravity dams and the development of cracks in the dam body. The outcomes highlighted the considerable effects of geometry and geotechnical properties on dictating the trajectory of crack growth.

Investigation of the microfracture and damage characteristics of dam during impoundment at Sanhekou hydropower station

Dam stability is one of the most important issues in hydraulic engineering. Microfractures and damage commonly occur during impoundment, which might lead to serious dam problems. In this study, based on the engineering background of the Sanhekou hydropower station, microseismic monitoring and numerical simulation were employed to systematically investigate the microfracture and damage characteristics of the dam body. First, the microseismic monitoring system was established to capture the microfractures inside the dam. The results indicated that the rise in water level elevation has a significant effect on the microfracture and damage characteristics of the dam body, especially during the early stage of impoundment. This can be reflected by the variation in the derived source parameters, i.e., the b value, daily energy release, daily apparent stress and daily apparent volume. In addition, the failure mode of the microfractures could be determined by using the ES/EP value of microseismic events and the moment tensor inversion method. The cracking orientation of the failure surfaces could also be determined by the moment tensor inversion method. Subsequently, numerical simulation was conducted where the initial damage of the dam was considered by integrating the microseismic monitoring data. The simulation results suggested that dam deformation under impoundment considering microseismic feedback agrees well with the real field measured results. The stress level of the dam toe was larger than that of the dam heel, and both the dam toe and dam heel were under compression before impoundment. However, with increasing water level elevation, the stress status of the dam heel area changes from compression to tension. The findings in this study will provide a better understanding of the damage and failure mechanism of dams during impoundment, which might be helpful for the design and support of dams in hydropower stations.

Liquefaction characteristics of aging earth dam body by dynamic centrifugal model test

Earth dams have been damaged or even collapsed owing to earthquake liquefaction. Although a liquefied foundation is a major factor affecting the safety of earth dams, the damage caused by the liquefaction of the dam body itself cannot be ignored, particularly for aged earth dams. However, in the presence of high water levels, liquefaction of the dam body cannot be considered solely in terms of the seismic load. Consequently, in this study we used dynamic centrifuge tests and numerical analysis to simulate the liquefaction process of an earth dam body under high water levels and analyzed the damage mechanism. The aging dam body, which can be easily liquefied, was simulated by controlling the density of the dam body, the low-density dam body exhibiting greater acceleration-amplification characteristics and displacement. Liquefaction was evident in the contact area between the slope and water level, with segmental settlement occurring. Through numerical analysis, it was evident that the core area accumulated considerable plastic deformation, and the sliding damage extended from the water contact surface to the dam toe. This study could compensate for the dearth of liquefaction model experiments of earth dams, providing a necessary reference for the seismic reinforcement of earth dams.

Analysis of Chloride Contaminant Transport in Tailings Storage Facility Dam (Case Study: Gold Mine in Sumatra)

In the practice of gold mining industry, hazardous waste known as tailings is produced during the ore extraction process. These tailings are typically stored in a dam structure called a Tailings Storage Facility (TSF). The planning and construction of a TSF are critical considerations, as the failure of a TSF can have substantial environmental impacts, pose risks to human safety, and result in industrial losses. Therefore, strict control is necessary in the development of TSFs to minimize the potential negative consequences. This research focuses on the transport of contaminants within a TSF, specifically examining the concentration of chloride contaminants and conducting particle movement analysis. The study utilizes modeling through the GeoStudio SEEP/W program to simulate groundwater flow profiles and the GeoStudio CTRAN/W program to understand contaminant movement over a 100-year period. GeoStudio modeling employs 10 materials: impermeable clay soil, filter sandy soil, transition gravel rock, three mine waste types (Fine, Rockfill, and Rockfill with fine), hard rock bedrock layer, in-situ soil representing the original layer, landslide with colluvial soil, and the tailings itself. Back analysis is employed to iterate model parameters and ensure modeling accuracy against field data, including comparisons with water quality test results and readings from vibrating wire piezometer (VWP) instrumentation. The contaminant transport is influenced by advection-dispersion processes and tends to concentrate within the TSF boundary toward the dam toe over a 100-year timeframe. The analysis emphasizes the influence of advection in contaminant transport and underscores the importance of particle position relative to the groundwater level, with Particle Tracking Analysis shows significant movement within the groundwater flow area. This research provides crucial insights into the dynamics of contaminant concentration, informing better decision-making in TSF planning and management. The findings underscore the imperative of strict control measures to minimize environmental impacts and human safety risks associated with TSFs, thereby advancing knowledge in gold mining waste management.

Feasibility Assessment of Medium-Scale Hydro-Power Plant – Case Study in Kerala, India

The power of the hydrological cycle is enormous, sometimes devastating, but when it is utilised wisely, its negative impacts on humankind can be mitigated. Catastrophic floods and droughts are boosted by the world climate change. Hence, water management programs came into effect. On the other hand, energy production plays a major role in the country’s economic development. So, studies have come up with many ideas to ameliorate disasters especially floods through building mini, small, and large hydro-power plants against the rivers. This study presents a feasibility analysis of flood management and energy production in the Madupetty River, Kerala, India. Even though there are other dams in the Madupetty River, Mudirappuzha basin, the old Headwork built for a hydroelectric project, needs capacity augmentation. This study looks at ways to optimise the Maduppetty River’s water distribution system by building a dam-toe powerhouse where flood water can be stored and utilised when needed. Detailed analysis and design of the hydro-power station is presented. Rainfall runoff equations are used to assess the inflow for power potential studies. During flooding, the projected dam can hold 20.42 MCM of water. From this study, the dam toe powerhouse and cascade powerhouses will create 7.12 Mu and 90 Mu.

Seepage Quantity Analysis Beneath Concrete Dams with Various Sheet Piles using Different Numerical Models

Seepage is a dangerous phenomenon under hydraulic structures and the main cause of failure and damage to dams when neglected and not processed. This study evaluates the numerical effects of the sheet piles' quantity, depth, and spacing beneath a concrete dam with isotropic and homogenous foundations on the seepage rate, pressure head, and exit gradient. The solutions were obtained using SEEP/W code in GeoStudio software 2018 for three configurations using single, double, and triple sheet piles. In addition, SLIDE software 6.02 was examined using single and double sheet piles. Dimensional analysis was applied to draw the dimensionless variables that affect the seepage rate and exit gradient, and all tests were repeated for three different sheet pile depths and distances from the heel of the dam. The findings showed that the seepage rate in all studied configurations reduced when sheet pile depth increased. The position of the sheet pile from the dam's toe significantly decreased the seepage rate in cases using single and double sheet piles, while in cases using three-sheet piles, the position of the middle sheet pile insignificant decreased seepage. It was recognized that when using a single sheet pile, the drop in pressure head increased with depths when the sheet pile was located at the heel and middle of the dam. In addition, in the case of a single sheet pile at the toe or using two and three-sheet piles, the pressure drop decreased as the depths increased. Also, the results showed that the middle sheet pile location in the case of three sheet piles slightly affected pressure reduction. Furthermore, the results showed that using two and three-sheet piles was more effective than using a single one in reducing the exit gradient, while the position of the middle one in the case of using three-sheet piles was insignificant. A nonlinear empirical equation was developed using SPSS 22 program, and the comparison of the seepage rate measured by SEEP/W and SLIDE software versus its quantity calculated from empirical equations showed a good agreement as the determinations (R2) coefficients were equal to 0.9779 and 0.9928, respectively.

Modal Analysis of Chushandian Gravity Dam

This article uses the finite element software ABAQUS to establish a three-dimensional finite element model based on the overflow dam section 12 # ~15 # and surface outlet dam section of the Chushandian gravity dam. The stress and displacement distribution of the 12 # ~15 # dam section of the Chushandian gravity dam under normal water storage level are analyzed; On this basis, modal analysis is conducted on the 12 # ~15 # dam section to study the impact of the dam's own modal conditions on the normal operation of the dam. The research shows that: (1) Under the condition of normal height water level, there is a small tensile stress at the dam heel, and the compressive stress at the dam toe is within the normal range. There is significant stress at the intersection of the upper curved part of the overflow dam and the transverse joint. The dam body strength meets the requirements and can be considered safe for the reservoir. (2) Modal analysis of the model reveals that significant deformation can occur at the right side of the dam crest during lower frequency vibrations. With the increasing frequency, the easily deformed parts of the dam are still at the top of the dam, and the displacement of the easily deformed parts is increasing. The position of the easily deformed parts is moving along the Dam axis, and the deformation direction of the easily deformed parts will change regularly.

Using the Morgenstern–Price Method and Cloud Theory to Invert the Shear Strength Index of Tailings Dams and Reveal the Coupling Deformation and Failure Law under Extreme Rainfall

It is difficult to obtain reliable shear strength parameters for the stability analysis and evaluation of tailings dams in an unstable state. In this study, the sensitivity of the shear strength index to the safety factor of a tailings dam was evaluated. The cohesion C range of a tailings earth rock dam in an unstable state is determined by the safety factor, and the Morgenstern–Price method is used for inversion. During parameter inversion, uncertainty reasoning is established based on cloud theory, which overcomes the problem that the fuzziness and randomness of the quantitative cohesion value are transferred to the qualitative concept of the safety factor. The results show that the change in cohesion C has a greater influence on the safety factor Fs of the tailings dam, and the value of parameter inversion is 8.6901 kPa. The deformation and failure of tailings dams under extreme rainfall conditions are analyzed by using the modified cohesion C value. The dam toe becomes the main response area of plastic deformation and slowly expands to the interior, showing creep deformation. The displacement field gradually transfers from the accumulated tailings to the tailings dam with the flow direction, causing erosion damage. This study provides a new idea and method for parameter inversion of the shear strength index of tailings dams and provides a reference for the disaster prediction and prevention of tailings dams subjected to extreme rainfall.

Experimental and numerical investigation of the trajectories of free and pressurized jets through storage dams

Abstract The purpose of this study is to investigate the trajectories of pressurized and free-falling jets and to determine their location downstream of the dam. The results show that the measured jet trajectory and the values extracted from the jet projectile equations are not the same. This discrepancy may be due to the effect of air resistance on flow; the existing jet trajectory equations do not incorporate air resistance. Projectile equations used for calculating the trajectory of falling jets have an average error of 21 and 26% for free-falling and pressurized jets, respectively. To minimize this discrepancy, the projectile equations were corrected. Also, the numerical simulation predicts the trajectories of the free and pressurized jets on average with a relative error (RE) of 25.5 and 23.5%, respectively, compared to the laboratory data. These errors can be caused by neglecting the effect of air resistance. In addition, it was found that by increasing the Froude number, the location of the falling jet impact moves further from the dam toe.

Multiscale Investigations of Overtopping Erosion in Reinforced Tailings Dam Induced by Mud-Water Mixture Overflow

The overtopping failure that occurred to the reinforced tailings dam has led to devastating catastrophes, including severe environmental disasters as well as tragedy in terms of any loss of properties and life. To study the feature of overtopping erosion for the reinforced fine-grained tailings dam induced by mud-water mixture overflow, the red mud concentration of overflow, the erosion depths and erosion rate have been consistently detected and recorded by a series of physical model tests. This investigation conclusively showed that the red mud concentration for flooding over the dam slope had a nonlinear trend of first becoming larger, subsequently decreasing with the time going on in the process of tailing dam overtopping; the maximum red mud concentration achieved 19.0%. The erosion on the dam slope was shaped like a trumpet. The red mud concentration of the mud-water mixture flow affected the erosion depth significantly. The hydraulic tests simulating erosion behaviour in the reinforced fine-grained tailings were carried out with different red mud concentrations (0%, 10%, and 20%). For the mud-water mixture flow in a red mud concentration of 20%, the final erosion depth exhibited a ladder shape from the front to the trailing end (dam toe) of the tailings sample. The final erosion depths were 1.56 cm, 0.9 cm, and 0.55 cm at the front, middle, and trailing end, respectively. With the red mud concentration decreasing, the final erosion depth at the front of the tailings sample reduced significantly while increasing at the trailing end. This study brought more scientific insights into the overtopping erosion process to the reinforced fine-grained tailings dam triggered by the mud-water mixture flow at multiscale.

On the Use of the H/V Spectral Ratio Method to Estimate the Fundamental Frequency of Tailings Dams

ABSTRACT This paper analyses the feasibility of estimating the fundamental frequency of an 85 m high cycloned-sand tailings dam located in the Central-North area of Chile using the single-station H/V Spectral Ratio Method (HVSR), calculated from seismic ambient noise and earthquakes recorded by a temporal seismic array deployed along the embankment crest, the downstream slope, and the dam toe, directly over the foundation soil. The fundamental vibration frequencies obtained from the HVSRs show consistency with results from the Standard Spectral Ratio method (SSR) calculated between the crest and the toe using the available earthquake records, particularly in the dam central part.

An Approach for Quantifying the Influence of Seepage Dissolution on Seismic Performance of Concrete Dams

Many concrete dams seriously suffer from long-term seepage dissolution, and the induced mechanical property deterioration of concrete may significantly affect the structural performance, especially the seismic safety. An approach is presented in this paper to quantify the influence of seepage dissolution on seismic performance of concrete dams. To connect laboratory test with numerical simulation, dissolution tests are conducted for concrete specimens and using the cumulative relative leached calcium as an aging index, a deterioration model is established to predict the mechanical property of leached concrete in the first step. A coupled seepage-calcium dissolution-migration model containing two calculation modes is proposed to simulate the spatially non-uniform deterioration of concrete dams. Based on the simulated state of a roller compacted concrete dam subjected to 100 years of seepage dissolution, seismic responses of the dam are subsequently analyzed. During which the nonlinear cracking of concrete, the radiation damping of the far-field foundation is considered. Research results show that seepage dissolution will seriously weaken the seismic safety of concrete dams because of the dissolution-induced decrease of effective thickness of the dam body. The upstream surface, dam toe and gallery wall suffer from a large degree of dissolution, whereas it is minimal and basically the same inside the dam body, at a degree of 0.19% within 100 years. The horizontal displacements of dam crest under the design static load and fortification against earthquake increase by 6.9% and 21.9%, respectively, and the dissolution-induced seismic cracking leads to the failure of dam anti-seepage system. This study can provide engineers with a reference basis for reinforcement decision of old concrete dams.

The Influence of Internal Erosion in Earthen Dams on the Potential Difference Response to Applied Voltage

Internal erosion is widely perceived as contributing to the failure of earthen dams. To reduce the failure risk, timely monitoring of internal erosion is an effective method in observing their internal structure evolution. A set of earthen dam model experiments were conducted. Under an applied voltage, the response potential differences (PD) at the slope of the dam models were collected before and after the impoundment of the upstream reservoir. The discrepancy among the four dam models, the influence of soil moisture content on PD, and the impact of internal erosion on PD were studied. The results show that it is acceptable to employ different dam models to simulate the development of internal erosion, although the discrepancy among the models is inevitable. The moisture content of the soil significantly affects the PD response to applied voltage. The PD increases with an increase in soil moisture content until the soil is saturated. The change in PD is correlated with the development of internal erosion. With the progression of internal erosion, the starting position for the steep increase in PD distribution continues to move toward the dam toe. In addition, the electrode stability is noted to have an effect on measured PD, which requires further studies to be clarified. This study sets the stage for the PD-based monitoring method in observing the evolution of internal erosion in earthen dams.

Experimental Investigation of the Outburst Discharge of Landslide Dam Overtopping Failure

Research on the factors and mechanisms that influence outburst floods are essential for estimating outflow hydrographs and the resulting inundation. In this study, large flume tests are conducted to investigate the effects of the upstream inflow and the presence of loose erodible deposits on the breaching flow and the subsequent outburst floods. Experimental results reveal that hydrographs of the breaching flow and outburst flood can be divided into three stages where each stage is separated by inflection points and peak discharges. It is found that the larger the inflow discharge, the larger the peak discharge of the outburst flood and the shorter the time needed to reach the peak and inflection discharges of the outburst flood. The breaching flow decreases along the longitudinal direction at rates that increase with the inflow discharge. The ratio between the length of the upstream dam shoulder and the dam width is inversely related to the ratio of the outburst discharge to inflow discharge. We also show that the presence of loose deposits at the dam toe can amplify the peak discharge of outburst flood by increasing the solids content of the water flow.

Large-scale field model tests of landslide dam breaching

The breaching of landslide dams is a severe geological disaster, and the resulting breaching floods significantly threaten people in downstream areas. In this study, a large-scale physical model was constructed in a natural river channel using unconsolidated dam material with a wide grain size distribution. Terrestrial laser scanning was used to capture three-dimensional geometric information of the landslide dam during the breaching process. The results showed that the dominant erosion pattern during dam breaching was surface progressive erosion. The breaching process could be divided into three stages based on different erosion characteristics: headward erosion, rapid erosion, and attenuated erosion. Longitudinal and lateral evolution models were proposed based on the field test results. The longitudinal evolution model describes the erosion at the dam crest and the sedimentation at the dam toe during the breaching process by defining the erosion and rotation points. The lateral evolution model revealed different lateral erosion characteristics at different cross-sections. Both the longitudinal and lateral evolution models were validated using two dam break events of the Baige landslide. The evolution models proposed in this study provide a scientific reference for numerical simulations of dam breaching and the prevention and mitigation of landslide dams.

Laboratory test and numerical simulation of composite geomembrane leakage in plain reservoir

Abstract Plain reservoir plays an important role in alleviating water shortage in plain areas which are generally crowded with large populations. As an effective and cheap anti-seepage measure, geomembrane is widely applied in plain reservoirs. Therefore, it is necessary to investigate the seepage discharge caused by composite geomembrane leakage. The laboratory test and numerical calculation are carried out in this paper to analyze the influence of three factors (i.e., water head, leakage size, and leakage location) on seepage discharge. It is found from the results of the orthogonal and single-factor analysis that the impact order of the three factors on the seepage discharge of plain reservoir is: distance from dam toe > water head > leakage size. Moreover, the seepage discharge increases as the water head, leakage size, and leakage quantity increase, in a linear relation. The opposite trend can be sawed in the seepage discharge when the distance from dam toe rises. Furthermore, a threshold distance is innovatively presented based on the results of numerical analysis. The ranking of three factors has enlightening significance for future scholars to track and study key issues of the leakage of composite geomembrane. The threshold distance presented in this paper is beneficial for engineers to manage and maintain the reservoir. Generally, the findings of this study can be beneficial to deepen the understanding of the influence of composite geomembrane leakage on the plain reservoirs.

Effects of toe configuration on throughflow properties of rockfill dams

Rockfill dams must be equipped with defence mechanisms to counteract the destabilizing effects of throughflow forces under accidental leakage scenarios. A key component of the rockfill dam overtopping system is the rockfill dam toe, constructed in tandem with the downstream rockfill shoulder. Quantitative descriptions of effects of different toe configurations on throughflow hydraulic properties of rockfill dams are currently unavailable in international literature. To address this, experimental investigations were conducted on 1 m high model rockfill dams with disparate toe configurations. Investigation outcomes describe the effects of internal, external and combined toe configurations on pore-pressure distributions within rockfill dam models subjected to throughflow conditions. Research outcomes provide vital information which can facilitate effective decision-making with regards to rockfill dam design. The accumulated data sets could also enable development, calibration and validation of numerical design tools and dam breach models.

3D Numerical Modelling of Tailings Dam Breach Run Out Flow over Complex Terrain: A Multidisciplinary Procedure

Tailings dams, as essential mining structures, are being built globally for containing the chief waste stream of the mining industry. Catastrophic tailings dam breaches have occurred frequently over the past decade, causing severe impacts on the environment, economy, and human health. The foreknowledge of the tailings dam breach overland flow is crucial for the risk assessment and emergency response planning in order to prevent or minimize possible losses. Using unmanned aerial vehicles (UAV) photogrammetry and smoothed particle hydrodynamics (SPH) numerical method, this study proposed a multidisciplinary procedure for modelling a hypothetical tailings dam breach run out flow over the downstream complex terrain. A case study on a 97-m-height tailings dam in Shandong Province of China was carried out. The proposed procedure was proven applicable to determine the overland tailings flow. The submerged area and flow velocities suggested that the downstream G2 highway would hardly be threatened and more concerns should be paid on the factory plants and workers deployed between the dam toe and the highway. Additionally, the application of UAV photogrammetry in the mining industry as a supplementary surveying method can be further expanded, especially for the numerous small-scale mining sites. The proposed procedure is then recommended for the safety management of the tailings’ storage facilities globally.

Study on the failure process and nonlinear safety of high arch dam and foundation based on geomechanical model test

The nonlinear safety is very important for the system of arch dam and its foundation since it is statically indeterminate structure and the geomechanical model test is effective method to evaluate the stability of arch dam. The analysis of failure process for a double-curvature arch dam with 167.5-meter-high, located in the northwest of China, has been carried out based on overload method. A quantitative method for determining the safety factor of initial nonlinear deformation of model test is proposed based on the Pearson product-moment correlation coefficient. Through the defromation evolution of all monitoring points, the nolinear safety has been determined. Then it is verified by acoustic emission data. By comparing the model test results of arch dam with other arch dams, the overall stability and safety of narrow valley arch dam is higher, and its failure mode is more dominated by foundation, while that of wide valley arch dam is more dominated by dam. The safety factor of initial nonlinear deformation, which has the same meaning as the control index of compressive stress safety of arch dam in the design specification, correspond to the compressive stress failure of the downstream dam toe.

Study on the nonlinear deformation and failure mechanism of a high arch dam and foundation based on geomechanical model test

Mengdigou double-curvature arch dam, located in the southwest of China, is a 200-meter-high dam with complex geological conditions. Failure analysis of the arch dam coupled with the foundation is important for evaluation of the stability. In this regard, a geomechanical model test was carried out. The data pertaining to displacements, stresses, and acoustic emissions, and the entire process of the failure occurring during overloading were obtained. During the overloading process, crack initiates in the upstream dam heel. Then, a crack appears downstream at the dam toe as the load increases. After the damage of the dam toe, cracks occur in the faults around the abutment. Meanwhile, cracks develop rapidly in the arch dam. Eventually, the dam-foundation system loses its ultimate bearing capacity and fails. The results of the model test were compared with those of numerical calculation. Then, the nonlinear deformation and failure mechanism was analyzed. Finally, the safety factor of cracking of the arch dam, the safety factor of the initial nonlinear deformation, and the safety factor of the ultimate bearing capacity were obtained, which reveal that the design of the arch dam is reasonable.