Dam Core Research Articles

Pressurised flow in cracks in embankment dam cores

A major hazard to embankment dams is internal erosion and piping arising from concentrated leaks through cracks in the core due to differential settlement. Previous work (Peirson et al., 2023) quantified the hydraulics of flow through near-surface transverse cracks subject to near-horizontal pressure gradients. This present short note extends the previous work to address pressurised flow through cracks that might occur deeper within the core. Water speeds, hydraulic shear stresses, flows are computed as a function of the applied hydraulic gradient. These results extend previous work addressing the hydraulics of very narrow cracks.

A hybrid approach combining UD and GA-CV-SVM to evaluate shear performance in high asphalt concrete core

The shear effect on high asphalt concrete core is significant. However, studies on the reliability of 100-meter-scale cores against shear damage remain limited. A key challenge in this research field is establishing the control criteria for the core and improving the computational efficiency of implicit limit state function (LSF). Additionally, the impact of material parameter uncertainty on the shear failure reliability of the core during the dam construction and impoundment stages remains unclear. To address this, a safety evaluation method based on time discretization was proposed, combining uniform design (UD), K-fold cross-validation (K-CV), and genetic algorithm (GA) to optimize the support vector machines (SVM). The core parameters of 52 asphalt concrete-core rockfill dams (ACCRDs) were analyzed, with the statistical values of the basic variables considered in determining the reliability index. The theoretical derivation of the critical shear failure safety index established a stability formula to assess the safety state of the dam core. The significance parameters were identified, and the sample points were generated at each stage using UD, and the Support Vector Regression (SVR) was applied to reconstruct the LSF, and reliability was calculated through the checking point method.

Seismic analysis of asphalt concrete core rockfill dams considering the bimodulus effect

In China, with the extensive development of pumped storage power stations, asphalt concrete core rockfill dams have become the preferred dam type because of their good deformation adaptability and impermeability. In seismic-prone western regions of China, the seismic safety of asphalt concrete cores is particularly important. However, asphalt concrete materials used in hydraulic engineering exhibit significant differences in their tensile and compressive moduli under low-temperature conditions, which has not been considered in existing constitutive models. In this study, a dynamic constitutive model considering the bimodulus effect of asphalt concrete was developed on the basis of dynamic tension and compression tests. Using this model, the influence of the bimodulus characteristics on the dynamic response of the core was investigated. The results indicate that a bimodulus constitutive model can effectively simulate the stress‒strain relationship of asphalt concrete materials at low temperatures. Compared with the bimodulus model, the use of the monomodulus model for calculations results in a significant decrease in compressive stress and a substantial increase in tensile stress of the core. Specifically, using the tensile and compressive monomodulus models led to maximum reductions in tensile stress of 42.9 % and an increase by 336.8 %, respectively. Neglecting the bimodulus effect may lead to misjudgment of the damage area, so the bimodulus effect on the seismic safety of dam cores should not be ignored.

Experimental Study on Key Techniques for the Construction of High Asphalt Concrete Core Rockfill Dam under Unfavorable Geological Conditions

Asphalt concrete core dams (ACCDs) have been widely constructed in Xinjiang, yet the design of materials and structures has mainly relied on empirical knowledge without substantial theoretical grounding. In this study, we carried out a large-scale relative density test of gravel material in Bamudun dam, studied the compaction characteristics of gravel material, and determined the relative density characteristic index, in order to provide a basis for the subsequent dam material rolling test and construction quality inspection. Furthermore, in order to improve the efficiency of dam construction in narrow valleys, we optimized the connection type between asphalt concrete core wall and bedrock, and proposed a rapid construction method of paving core wall after pouring mass concrete base on bedrock. Finally, we established a three-dimensional finite element model to systematically analyze the stress and deformation patterns of the dam body, core wall, and base of the ACCD at Bamudun. The results show that the maximum compressive stress suffered by the core wall during the full storage period is 1.62 MPa, there is no tensile stress, and the risk of hydraulic splitting is small. The stress and deformation levels of each part are within the safe range. This verifies the rationality of the rapid construction method. The research findings can provide a great theoretical significance and engineering value for the safe design and construction of ACCDs.

Presenting the AI models in predicting the settlement of earth dams using the results of spatiotemporal clustering and k-means algorithm

In this work, the results of instrumentation over 8 years, including the phases of construction, first impounding, and operation, have been used to analyze the location of the Eyvashan Dam settlement. Mohr–Coulomb behavioral model and numerical model of Plaxis 2D software were used to verify the monitoring results. The results demonstrated that settlement of the dam has increased in the dam's core since the beginning of construction, and they eventually stabilized during the operation phase. After the completion of the construction phase, the maximum settlement of the dam core was recorded as 809 mm, which is equivalent to 1.2% of the height of the dam at the middle level. Also, an approach to interpreting the settlement behavior of earth dams has been presented that is based on spatiotemporal clustering. Also, RF, MARS, and GMDH models were created based on a proposed scenario to predict settlement using points located in a cluster. Therefore, the settlement location of the studied dam was determined using the results of the k-means clustering algorithm in the aforementioned AI models. The high accuracy of the results of the proposed method confirms the proper performance of using AI models in predicting and diagnosing the settlement of earthen dams using the results of k-means spatiotemporal clustering algorithm. The evaluation of the models shows that the ENN model is a more suitable and efficient tool in this field and can be useful in monitoring the settlement of earth dams.

Random dynamic response analysis of an asphalt concrete core wall dam on deep overburden with double random factors

The spatial variability of material parameters and the randomness of ground motion are factors that influence the seismic response of a dam. To obtain more reliable seismic response results, it is crucial to study the influence of various uncertain factors on the response to earthquakes. In this paper, the K-L series expansion method and LH sampling technique are combined to characterize the spatial correlation of material parameters using a Gaussian autocorrelation function. This allows for the simulation of random fields of material parameters. By improved the Clough-Penzien power spectrum model and incorporating the concept of a random function, it becomes possible to generate nonstationary random ground motion that accurately reflects the site conditions. Taking an asphalt concrete core dam on deep overburden as an example, a random dynamic response analysis was conducted, considering various random factors. Statistical analysis and distribution testing were conducted on the horizontal acceleration and vertical permanent deformation responses. The process of the evolution of the probability density of the horizontal acceleration at the top of the dam was determined using the generalized probability density evolution method. This method helps to reveal the influence of various random factors on the response of the dam body. The research results show that among the spatial variability of material parameters and the randomness of ground motions, the randomness of ground motions is the main influencing factor of the random response results of the dam body. The mean response of two random factors is significantly larger than that of a single random factor. When considering dual random factors simultaneously, the complexity of the random factors increases, resulting in statistical properties that differ from those of single random factors. Therefore, to obtain more reliable random seismic response results, it is necessary to consider both the spatial variability of material parameters and the randomness of ground motions.

Monitoring of Älvkarleby test embankment dam using 3D electrical resistivity tomography for detection of internal defects

Electrical resistivity tomography (ERT) is a potential-based method for detecting internal erosion in the core of embankment dams using the electrodes installed outside. This study aims at evaluating the practical capability of ERT monitoring for detecting internal defects in embankment dams. A test embankment dam with in-built well-defined defects was built in Älvkarleby, Sweden, to assess different monitoring systems including ERT and the defect locations were unknown to the monitoring teams. Between 7500 and 14,000 ERT data points were acquired daily, which were used to create the distribution of electrical resistivity models of the dam using 3D time-lapse inversion. The inversion models revealed a layered resistivity structure in the core that might be related to variations in water content or unintentional variations in material properties. Several anomalous zones that were not associated with the defects were detected, which might be caused by unintentional variations in material properties, temperature, water content, or other installations. The results located two out of five defects in the core, horizontal and vertical crushed rock zones, with a slight location shift for the horizontal zone. The concrete block defect in the core was indicated, although not as distinctly and with a lateral shift. The two remaining defects in the core, a crushed rock zone at the abutment and a wooden block and a crushed rock zone in the filter, were not discovered. The results cannot be used to fully evaluate the capability of ERT in detecting internal erosion under typical Swedish conditions due to limited seepage associated with the defects. Furthermore, scale effects need to be considered for larger dams.

Spatiotemporal clustering of dam settlement monitoring using instrumentation data (case study: Eyvashan Earth Dam)

The integrity of monitoring data is important for studying the amount and location of deformation in earth dams. In this research, the meeting of the Eyvashan Earth Dam was analyzed using the results of precision instruments over a period of eight years during three periods of construction, first impoundment, and exploitation. To verify the accuracy of the results, the numerical model of the largest section of the dam was constructed with Plaxis software and analyzed according to the Mohr–Coulomb behavior model. The results showed that since the beginning of construction, the occurrence of settlements in the core of the dam has been increasing, and with the passage of time, settlements reach a constant value in the operation phase. The maximum settlement of the dam core at the end of the construction stage was 809 mm, which was equal to 1.2% of the dam height in the middle level. Additionally, an approach based on spatiotemporal clustering has been presented to improve the interpretability of the settlement behavior of earth dams. Clustering analysis of spatiotemporal data is used as a measure to determine the similarity of settlements and to select relevant data. Therefore, k-means clustering algorithms and two-step clustering were used to determine the displacement of earth dams. By comparing the correlation results, the proposed method of detecting settlement areas using a spatiotemporal clustering model can be considered a reliable method for monitoring the settlement of earth dams.

Influence of difference in deformation modulus between asphalt concrete core and transition layer on core behavior and difference threshold determination

Asphalt concrete core is the main impermeable structure of asphalt concrete core dams (ACCDs). The deformation modulus difference between the core and transition layer is directly related to the core behavior, especially the arch effect. This paper mainly studies the threshold of the deformation modulus difference between the transition and asphalt concrete core and the core arc safety. A database of 54 ACCD cases from domestic and abroad is collected. The thickness and material characteristics of the transition and core are statistically analyzed, and the range of deformation modulus ratio η between them is determined. A numerical model is established, and the impact of different interface models on the core behavior is compared and analyzed. By comparing measured data and numerical calculation results, an appropriate interface simulation method is selected to study the influence of deformation modulus ratio η on the core performance. On this basis, the threshold ηmax is determined using a cusp catastrophe model. A new valley shape characterization parameter δ is proposed, and the arch safety area under different δ is studied based on ηmax for reference in ACCDs design and construction. Finally, engineering measures to enhance the arch safety of the core are discussed.

Wall and pillar drains in puddle clay embankment dams

Puddle clay core embankment dams were built prior to the use of rolled clay core dams and comprise a large proportion of UK dams, with the dams relying for their watertightness on the addition of water to (puddle) the clay until it has an undrained shear strength of around 10 kPa, and thus has increased ability to deform without cracking. Such dams sometimes had early forms of unfiltered drains, comprising coarse cobbles, in the downstream shoulder, either to assist construction and/or to lower the phreatic surface and improve the slope stability once the reservoir is in operation. These drains are separate from foundation drains dealing with springs encountered in the foundation excavation and drains to deal with surface runoff. This paper gives examples of such drains in dams constructed between 1863 and 1940. These drains were installed prior to the development of classic filter design rules and tools to analyse seepage. This is important as the drains have no filter, and are thus vulnerable to internal erosion which, if not detected, could lead to failure of the dam. These drains may also be the true root cause of historic incidents at these dams, due to embankment fill materials washing into the drain and creating sinkholes.

Утилизация промышленных и муниципальных отходов для предотвращения опасного роста температуры атмосферы Земли

In order to assist enterprises in solving their environmental problems, the author has spent over 60 years developing methods (compositions and technologies) for using about 100 different types of industrial and municipal waste (IMW) as raw materials for producing new environmentally friendly materials with the properties of concrete without Portland cement, ceramics, glass ceramics, refractories, plaster, heat and sound insulators, new types of fuel with increased calorific value, foundations for highways, airfields, urban and industrial landfills, dam cores, etc. As a result of field tests conducted in various regions, including Siberia and the North of the country, the developed compositions and technologies for creating foundations for highways were included in the building codes SN 25-74 [3] of the former USSR and are widely used in construction practice. Currently, the author is implementing projects for branches of international concerns RENAULT, VOLVO, BOSCH, ODEBRECHT, PETROBRAZ, SANEPAR, KOSELPA and other enterprises and municipalities of Brazil on the use of their PMO for the production of new, primarily building materials with high economic and environmental efficiency.

Model tests and numerical simulation of overtopping-induced breach process of the asphalt concrete core dam

Although asphalt concrete core dams have been widely constructed, the mechanism of overtopping-induced dam breaches during catastrophic floods remains unclear, especially concerning the structural failure process of the core wall. This study utilizes a flume model test system to examine the overtopping-induced breach process of an asphalt concrete core dam based on the Sheyuegou Dam breach case in Xinjiang, China. The model tests showed the continuous erosion of dam shell material and structural failures of the core wall during dam breaching, highlighting the significant impact of the erosion-resistant asphalt concrete core wall on the dam breach process. The overtopping breach process of an asphalt concrete core wall dam can be divided into three stages: the asphalt concrete core wall is gradually exposed by backward erosion of the dam shell material until the first structural failure occurs; one or multiple structural failures of the core wall happen due to breach enlargement by continuous erosion of dam shell material until peak breach flow is reached; multiple structural failures of the core wall take place as the breach in the dam shell deepens and widens until breach morphology stabilizes. A numerical model is developed to simulate the overtopping-induced breach process of the asphalt concrete core dam based on the breach model tests. This model utilizes a soil erosion formula to estimate the dam shell material's erosion rate and calculate the exposed length of the asphalt concrete core wall. In addition, the moment balance method is employed to determine the overturning moment and length at each structural failure and the overturning instances of the exposed core wall due to hydrodynamic force and soil pressure. A notable feature of the numerical model is its ability to depict the coupled effects of soil erosion and structural failures of the asphalt concrete core wall during dam breaching. This numerical model is applied to a back analysis of the Sheyuegou dam breach process. The comparison between measured and calculated results indicated that the breach hydrograph and breach evolution process accurately represent the actual breach process of the Sheyuegou dam, with the relative errors of essential dam breaching parameters remaining within ±25 %. Sensitivity analysis showed that the thickness variation of the asphalt concrete core wall significantly influences the dam breach process, with the order of impact on critical breaching parameters being time to peak, final breach size, and peak breach flow. The results provide valuable insights into the simulation of the overtopping failure process of asphalt concrete core dams.

Use of recycled ceramic beads to enhance mechanical behavior of low-plastic clays

Due to the huge amount of annual non-renewable ceramic waste disposal, it is in favor of eco-system to reuse the ceramic waste in earthwork structures. Thus, among several different applications of ceramic components, they can also be used to replace aggregates in the core of embankment dams, waste disposal projects and to form subgrade of roads and railways. The main issues addressed in this study are the effect of the volumetric content and size of the ceramic inclusions on the mechanical properties of ceramic-clay mixtures. Using an experimental approach, strain-controlled monotonic, stress-controlled cyclic, and post-cyclic monotonic triaxial undrained tests were made. The innovation of this study is that sphere beads of ceramic with different diameters were added to low-plastic clay to explore the role of bead size on the mechanical properties of bead and clay mixtures under monotonic, cyclic and post-cyclic loadings. Thus, we tested four types of specimens consisting of merely pure clay, 80% clay–20% bead, 60% clay–40% bead, and 40% clay–60% bead. Scanning electron microscope (SEM) images were additionally used to investigate the fabric of the clay between the ceramic beads. Test results revealed, firstly, that effective friction angle and undrained shear strength increase with the bead content. Secondly, dilative behavior was captured in all the bead and clay mixtures. Further, both dynamic shear modulus and damping ratio increase with the bead content. Similarly, post-cyclic shear strength increases with the bead content. Finally, different bead diameters did not change the observed trend.

Assessing dam spillway discharge capacity in response to extreme floods in Perak river hydroelectric scheme: Simulation and proposed mitigation measures

The aged dams in Perak river Hydro-Electric Scheme (HES) have been constructed decades ago and a common concern raised during dam safety reviews is that they were not designed to safely reroute the Probable Maximum Flood (PMF) but rather the Inflow Design Flood (IDF) of 1,000 years’ design floods. Failure due to the insufficient spillway discharge capacity has been identified as one of the primary causes leading to overtopping. This applied research has thus been initiated to evaluate the spillway discharge capacity of dams in response to PMF extreme flooding. Besides, the safety of the dams has been evaluated by calculating the highest flood level achieved in response to the specified extreme floods. In order to simulate PMF hydrographs, various durations of Probable Maximum Precipitation (PMP) have been calculated using Hershfield statistical approach based on historical annual maximum rainfall statistics. Using a calibrated and validated hydrological model developed in HEC-HMS, PMF simulation was performed. It was discovered that the PMF generated at 120 hrs (5 days) resulted in the maximum flood level for all dams/reservoirs. The achieved highest PMF flood levels are still lower than the designated dam core and crest level in respective dams, indicating that the dams in Perak river HES are safe from overtopping failures during the occurrences of extreme events up to PMF level. While routing the worst-case scenario over 120 hr, the maximum spillway discharges predicted for Temengor and Bersia are beyond their design capacity, while Kenering and Chenderoh remain within design limits. Mitigation that will be implemented to minimize the possibility of risks to occur include improvement of emergency management system and dams monitoring data collection. It is anticipated that the outcomes of this applied research will be adopted for development of Risk Informed Decision Making (RIDM) frameworks for dams in Perak river HES in future.

Dynamic Characteristics of Asphalt Concrete as an Impervious Core in Embankment Dams under Varying Temperatures and Stress States.

To reveal the dynamic characteristics of asphalt core embankment dams (ACEDs), we carried out a dynamic triaxial experiment on hydraulic asphalt concrete (HAC) under different temperatures (T = 4 °C, 10 °C, 16 °C, and 22 °C) and stress states (Kc = 1.0, 1.2, 1.4, and 1.6; σ3 = 0.5, 0.6, 0.7, and 0.8 MPa). The results indicate that HAC's maximum dynamic elastic modulus increased with decreasing temperature, increasing principal stress ratio, and increasing confining pressure. However, the damping ratio showed the opposite trend. Moreover, in order to study the deformation capacity of HAC, 300 cyclic loads were applied to some specimens. At a temperature of 22 °C, the specimens had a tendency to deform axially, but not significantly. With a decrease in temperature, the axial deformation tendency of the specimen gradually weakened or even disappeared. However, a small number of cracks appeared in the aggregate and between the asphalt and the aggregate of the specimen. In order to quantify the dependence of dynamic parameters on temperature, the temperature influence factor of the maximum dynamic elastic modulus and the temperature sensing factor of the damping ratio were defined. The variation in the temperature influence factor of the maximum dynamic elastic modulus with temperature can be described by a logistic function. The temperature sensing factor of the damping ratio increased with an increasing principal stress ratio and peripheral pressure. Finally, maximum dynamic elastic modulus and damping ratio computational models for the interaction of temperatures and stress states were developed using the normalization method. Upon comparison, the dynamic parameters were observed to be very close to those listed in the literature, which verifies the applicability of the computational models of the maximum dynamic elastic modulus and damping ratio.

Relationship between Porosity and the Modified Constitutive Model Parameters of Asphalt Concrete Core Material

Porosity is a key control index for ensuring the compaction quality of rockfill dams with asphalt concrete cores. The porosity of the asphalt mixture is an important factor for an asphalt concrete core dam to obtain adequate strength and control the core deformation. However, the compaction quality (i.e., porosity) of the asphalt core wall inevitably exhibits spatial differences during actual construction process. To analyze the quantitative relationship between the porosity of the asphalt concrete core and the Duncan-Chang model parameters, triaxial tests under different confining pressures were carried out with asphalt concrete samples of different porosities. Based on the test results, the applicability of the Duncan-Chang model was assessed. Aiming at the limitation of the Duncan-Chang model, which is unable to characterize the strain softening and shear dilatancy of materials, a modified constitutive model of the asphalt concrete core was proposed. The determination method of the proposed model parameters was provided and verified by triaxial test results. A regression relationship was established between the porosity of the core material and the parameters of the modified constitutive model. This study provides a prerequisite for conducting refined finite element analysis on the mechanical performance of the asphalt core rockfill dams, taking into account the spatial differences in compaction quality of the asphalt concrete core.

Simulating the Hydraulic and Volume Change Behavior of Compacted Highly Expansive Soil under Potential Field Stress and Seasonal Climatic Variation

A sustainable design of some engineering applications, such as earth dam cores, landfill liners, clay barriers, and radioactive waste disposal systems, that utilize compacted expansive soils requires simulation for probable field conditions. This study investigated the hydraulic and volume change (H-VC) behaviors of highly expansive compacted soils in Al-Qatif city under different seasonal climatic variations for a wide range of stress conditions, aiming for more economical and rational design and practices. The extent of the effect of the start cycle condition of the cyclic wetting and drying (W/D) process on the examined properties is examined, as well. Two testing series of the cyclic W/D process, representing the probable seasonal climatic variations, were executed for varied axial stress conditions. The H-VC behaviors of expansive soils are affected by the simulated seasonal variation (i.e., cyclic W/D process), with the first cycle of W/D being the most effective cycle and an elastic state being attained by the third to fourth cycle. Swell fatigue is noted for both testing series, and this is attributed to the initial placement condition. Analysis of results recommends exposure of the compacted expansive soil layers in the field to drying after compaction to reduce their equilibrium wetting potential. As a consequence of the noted shrinkage accumulation, a reduction tendency of saturated hydraulic conductivity (ksat) with repeated W/D cycles is reported for both series under all the stress states applied. Finally, it is recommended for clay barrier projects to be submerged once compacted to obtain barriers with the lowest values of hydraulic conductivity.

Influences of Paraffin-Based Phase Change Material on Soil Engineering Properties

Paraffin-based phase change materials (PPCMs) have been recognized as a potential tool to regulate soil temperature and reduce the freeze–thaw impact on soil. However, as a new filling material for geotechnical structures, such as dam core walls, the engineering applicability of PPCM-mixed soil (PS) needs to be further studied. In this paper, the influences of PPCM on the soil engineering properties (i.e., compaction characteristics, consolidation properties, mechanical behaviors, and permeability) and the PPCM leakage behavior were studied through a series of laboratory experiments. The results showed that the addition of PPCM results in an obvious decrease in the maximum dry density and optimum water content, a slight change in the compression coefficient, a significant reduction of the plasticity and cohesion, and an enhancement of the friction angle and impermeability. In addition, the PPCM in PS specimens will leak under the constant hydraulic gradient or vacuum saturation, and the leaked mass is positively related to the initial PPCM content. The PS specimens after 64-day seepage will still have a good impermeability. This paper is an important prerequisite for the practical applications of PS and provides a basis for its performance improvement.

Seismic Response of a Rockfill Dam with an Asphalt–Concrete Core under P Waves with Arbitrary Incident Angles

The incident angles of seismic waves have a significant influence on the seismic response of asphalt–concrete core rockfill dams. This paper constructs the free field of elastic semispace under P waves with arbitrary incident angles and clarifies the variation law of the seismic intensity on the ground surface with incident angles γ and α. The free field on the foundation boundary under arbitrary combinations of angles γ and α are derived according to the wave-field superposition principle. Combined with the viscoelastic artificial boundary, the free field is transformed into the equivalent load on the boundary node, and the input method of the P wave with arbitrary incident angles is established. Finally, the seismic response of the asphalt–concrete core dam under P waves with arbitrary incident angles is studied. The results show that when the incident direction is perpendicular to the dam axis, the dynamic shear stress is the highest, and the local seismic safety factor of the dam is the largest. When the incident direction is parallel to the dam axis, the tensile stress of the asphalt core is the highest, there is a possibility of cracking at the contact part of the lower part of the asphalt core with the canyon, and the seismic subsidence rate of the dam crest is the highest. For the tensile stress of the asphalt core and the dam-crest subsidence rate, the most unfavorable incident angle α is 75° when the incident angle γ is the same.

Studi Karakteristik Propertis Tanah di Kecamatan Polen Kabupaten TTS

Knowing soil characteristics is very important for an engineer to ensure the safety of buildings above the ground. Therefore, conducting a soil investigation in the laboratory and field testing The island of Timor, especially in the Polen sub-district, Timor Tengah Selatan district, has fine-grained soil deposits. In the sub-district area, a large dam is being built, namely the Temef Dam and the main road link connecting one city and four regencies on the island of Timor also. This study aims to determine the characteristics of the soil both physically and mechanically through laboratory testing. The results showed that the location in Puna Village was clay of low plasticity, while the Loli Village had high plasticity clay deposits. The higher of soil's plasticity index, the higher the potential for swelling of the soil. The increased swelling potential causes the low shear strength of the soil. Clay with low shear strength cannot support the construction load on it. Therefore, before the construction of the building on it, it is necessary to improve the soil. In addition to its weaknesses, on the other hand, impermeable clay is used in the dam core material, where the location of material extraction is still within reach so that the work becomes economical.