Search Results (60)

This study conducted uniaxial creep tests on coal samples under both natural and water-saturated conditions for durations of about 180 days per sample to study the stability of coal pillar dams of the Daliuta Coal Mine underground reservoir. Combined with synchronized acoustic emission (AE) monitoring, the research systematically revealed the time-dependent deformation mechanisms and damage evolution laws of coal under prolonged water immersion and natural conditions. The results indicate that water-immersed coal exhibits a unique negative creep phenomenon at the initial stage, with the strain rate down to −0.00086%/d, attributed to non-uniform pore compaction and elastic rebound effects. During the steady-state creep phase, the creep rates under water-immersed and natural conditions were comparable. However, water immersion led to an 11.4% attenuation in elastic modulus, decreasing from 2300 MPa to 2037 MPa. Water immersion would also suppress AE activity, leading to the average daily AE events of 128, which is only 25% of that under natural conditions. In the accelerating creep stage, the AE event rate surged abruptly, validating its potential as an early warning indicator for coal pillar instability. Based on the identified long-term strength of the coal sample, it is recommended to maintain operational loads below the threshold of 9 MPa. This research provides crucial theoretical foundations and experimental data for optimizing the design and safety monitoring of coal pillar dams in CMURs. Full article

Earth fill dams are susceptible to internal erosion and instability when founded over cavity-prone formations such as gypsum or karstic limestone. Subsurface voids can significantly compromise dam performance, particularly under seismic loading, by altering seepage paths, raising pore pressures, and inducing structural deformation. This study examines the influence of cavity presence, location, shape, and size on the behavior of zoned earth dams. A 1:25 scale physical model was tested on a uniaxial shake table under varying seismic intensities, and seepage behavior was observed under steady-state conditions. Numerical simulations using SEEP/W and QUAKE/W in GeoStudio complemented the experimental work. Results revealed that upstream and double-cavity configurations caused the greatest deformation, including crest displacements of up to 0.030 m and upstream subsidence of ~7 cm under 0.47 g shaking. Pore pressures increased markedly near cavities, with peaks exceeding 2.7 kPa. Irregularly shaped and larger cavities further amplified these effects and led to dynamic factors of safety falling below 0.6. In contrast, downstream cavities produced minimal impact. The excellent agreement between experimental and numerical results validates the modeling approach. Overall, the findings highlight that cavity geometry and location are critical determinants of dam safety under both static and seismic conditions. Full article

Cracks and seepage in dam structures pose a serious risk to their safety, yet traditional inspection methods often fall short when it comes to detecting shallow or early-stage fractures. This study proposes a new approach that uses spectral response analysis to quickly identify signs of seepage in concrete dams. Researchers developed a three-layer model—representing the concrete, a seepage zone, and water—to better understand how cracks affect the way electrical signals behave, thereby inverting the state of the dam based on how electrical signals behave in actual engineering measurements. Through computer simulations and lab experiments, the team explored how changes in the resistivity and thickness of the seepage layer, along with the resistivity of surrounding water, influence key indicators like impedance and signal angle. The results show that the “spectrum-based method” can effectively detect seepage in concrete cracks of dams, and the measurement method of the “spectral quadrupole method” based on the “spectrum-based method” is highly sensitive to these variations, making it a promising tool for spotting early seepage. Field tests backed up the lab findings, confirming that this method is significantly better than traditional techniques at detecting cracks less than a meter deep and identifying early signs of water intrusion. It could provide dam inspectors with a more reliable way to monitor structural health and prevent potential failures. Full article

It is vital to stabilize pillar dams in underground reservoirs in coal mine goafs to protect groundwater resources and quarry safety, practice green mining, and protect the ecological environment. Considering the actual occurrence of coal pillar dams in underground reservoirs, acoustic emission (AE) mechanical tests were performed on dry, naturally absorbed, and soaked coal samples. According to the mechanical analysis, Quantitative analysis revealed that dry samples exhibited the highest mechanical parameters (peak strength: 12.3 ± 0.8 MPa; elastic modulus: 1.45 ± 0.12 GPa), followed by natural absorption (peak strength: 9.7 ± 0.6 MPa; elastic modulus: 1.02 ± 0.09 GPa), and soaked absorption showed the lowest values (peak strength: 7.2 ± 0.5 MPa; elastic modulus: 0.78 ± 0.07 GPa). The rate of mechanical deterioration increased by ~25% per 1% increase in moisture content. It was identified that the internal crack development presented a macrofracture surface initiating at the sample center and expanding radially outward, and gradually expanding to the edges by adopting AE seismic source localization and the K-means clustering algorithm. Soaked absorption was easier to produce shear cracks than natural absorption, and a higher water content increased the likelihood. The b-value of the AE damage evaluation index based on crack development was negatively correlated with the rock damage state, and the S-value was positively correlated, and both effectively characterized it. The research results can offer reference and guidance for the support design, monitoring, and warning of coal pillar dams in underground reservoirs. (The samples were tested under two moisture conditions: (1) ‘Soaked absorption’—samples fully saturated by immersion in water for 24 h, and (2) ‘Natural absorption’—samples equilibrated at 50% relative humidity and 25 °C for 7 days). Full article

This article analyses the necessity of employing an interdisciplinary approach in the geotechnical practice of designing, constructing, and operating industrial hydraulic structures—tailings dams of processing plants. Tailings dam failures often lead to irreversible consequences for the ecological state of the environment. The interdisciplinary approach involves treating the foundation soils of structures and anthropogenic tailings deposits as a multicomponent system. In this system, soil acts as a medium hosting groundwater of varying compositions and contamination levels, containing biotic components and their metabolic products, including the gaseous phase. It has been demonstrated that the justified application of this approach increases the operational safety of existing structures and the long-term stability of starter and tailings dikes built on weak clay foundation soils. Particular emphasis is placed on the biotic component and the dual role of subsurface microorganisms. These bacteria negatively impact the strength and load-bearing capacity of water- and water–gas-saturated clay soils in the foundation of the structures under consideration. The diverse biocenosis in groundwater simultaneously facilitates self-purification from petroleum hydrocarbons to undetectable levels. This aspect holds fundamental importance, as groundwater discharges into river systems. Full article

With the increasing service duration of dams, the analysis of seepage pressure monitoring data plays a crucial role in ensuring the safety of seepage behavior. However, seepage pressure monitoring systems are often subject to environmental disturbances, sensor failures, and other interfering factors, leading to anomalous measurements during data acquisition. To objectively reflect the true operational state of dams and address the limitations of conventional detection and identification methods—such as low efficiency, high subjectivity in evaluation, and ineffective recognition of multi-category outliers—this study constructed an online detection, identification, and correction method for multi-category anomalous values. Specifically, an enhanced particle filter incorporating a Bernoulli probability model is constructed to characterize multi-category outliers in seepage pressure monitoring data, building upon the traditional particle filter framework. Following online detection and identification, the MissForest imputation method is employed to rectify the anomalous values. In the case study, both the false detection rate and missed detection rate ranged between 0% and 10%. Comparative experiments with three alternative methods revealed significant differences in data reconstruction performance, with the proposed method achieving the highest R² score (0.861) and the lowest RMSE (0.050) and MAE (0.052). The results demonstrate that the proposed method effectively identifies outliers, achieves superior reconstruction of seepage pressure data, and minimizes errors. Furthermore, this research provides a novel approach for detecting anomalous seepage pressure measurements and evaluating dam safety conditions. Full article

To overcome the limitations of rigid body limit equilibrium methods in earth rock dam slope stability analysis, this study develops a system reliability framework using the finite element strength reduction method (FEM-SRM). An elastoplastic finite element model simulates dam construction and impoundment, identifying potential slip pathways. Each pathway, treated as a parallel system of shear-failed elements, is analyzed via the response surface method to derive explicit limit state functions. Reliability indices are computed using an improved first-order second-moment method, while interdependencies are assessed through stepwise equivalent linearization. System reliability is determined using Ditlevsen’s narrow bound method. Applied to a 314 m earth rockfill dam, three critical slip pathways were identified: upstream shallow (reliability index is 6.94), upstream deep (reliability index is 6.87), and downstream deep (reliability index is 7.44), with correlation coefficients between 0.26 and 0.89. The system reliability index (6.81) significantly exceeds the code target (4.2), highlighting the method’s ability to integrate material randomness, stress-strain nonlinearity, and multi-slip interactions. This framework provides a robust probabilistic approach for high earth rock dam stability assessment, enhancing engineering safety evaluations. Full article

Thermal stress control is crucial for massive concrete structures during construction. The cooling strategies directly determine the safety of structures, material quality, construction efficiency, and project cost. However, precise spatiotemporal thermal stress regulation and management are difficult to achieve due to the lack of balanced discriminant criteria and multi-objective optimization methods for the selection of traditional strategies. Therefore, an intelligent optimization method for thermal stress management strategy in massive concrete structures, considering the balance of safety, quality, efficiency, and cost (SEQC-TSOM), is proposed. Initially, a Thermal Stress Simulation Mechanism Model (TSSM) is constructed to accurately evaluate the structural state throughout the entire process. Subsequently, a mechanism data-driven surrogate model (MD-SM) is constructed to quickly evaluate the structural response under different cooling strategies. Furthermore, a multi-objective intelligent optimization model and a multi-criteria decision-making model are proposed to filter the intelligent optimal strategy from the Pareto solution set. Finally, a case study based on the Baihetan arch dam project is conducted, and the results show that the safety, quality, efficiency, and cost (SEQC)-balanced strategy increases safety by 42%, improves cooling efficiency by 36%, and reduces cooling costs by 20.6% compared with traditional strategies. Full article

Strategically important objects, such as dams, tunnels, bridges, and others, require long-term structural health monitoring programs in order to preserve their structural integrity with minimal downtime, financial expenses, and increased safety for civilians. The current study focuses on developing a damage detection methodology that is applicable to the long-term monitoring of such structures. It is based on the identification of resonant frequencies from operational modal analysis, removing the effect of environmental factors on the resonant frequencies through support vector regression with optimized hyperparameters and, finally, classifying the global structural state as either healthy or damaged, utilizing the Mahalanobis distance. The novelty lies in two additional steps that supplement this procedure, namely, the nonlinear estimation of the relative effects of various environmental factors, such as temperature, humidity, and ambient loads on the resonant frequencies, and the selection of the most informative resonant frequency features using a non-parametric neighborhood component analysis algorithm. This methodology is validated on a wooden two-story truss structure with different artificial structural modifications that simulate damage in a non-destructive manner. It is found that, firstly, out of all environmental factors, temperature has a dominating decreasing effect on resonance frequencies, followed by humidity, wind speed, and precipitation. Secondly, the selection of only a handful of the most informative resonance frequency features not only reduces the feature space, but also increases the classification performance, albeit with a trade-off between false alarms and missed damage detection. The proposed approach effectively minimizes false alarms and ensures consistent damage detection under varying environmental conditions, offering tangible benefits for long-term SHM applications. Full article

Geotechnical field testing evaluates soil, rock, and groundwater conditions in their natural states, offering critical information about subsurface properties such as the density, strength, permeability, and groundwater flow. These tests are essential in ensuring the safety, reliability, and performance of civil engineering projects and are increasingly used for 3D geographical visualization and subsurface modeling. While point-based tests like the cone penetration test (CPT) and standard penetration test (SPT) are widely used, area-based methods such as the spectral analysis of surface waves (SASW) and electrical resistivity testing significantly enhance the accuracy of such models by providing broader coverage. Furthermore, these non-destructive techniques are particularly effective in identifying subsurface defects. This study focuses on analyzing the data acquisition areas of various field seismic tests, including SASW, downhole, crosshole, and suspension logging (PS logging). While other tests clearly define data acquisition areas based on their array paths, the SASW test posed challenges due to the complexity of data reconstruction. To address this, 69 datasets from four different sites were analyzed to predict the data acquisition areas for SASW as a function of depth. Moreover, a case study demonstrates the practical application of the SASW method in detecting cavities near a dam spillway. The findings of this research improve the understanding and interpretation of geotechnical seismic test data, enabling more precise geotechnical investigations and advancing the detection of subsurface defects using non-destructive methods. Full article

Adopting an appropriate method to analyze the spatial evolution process of tailings flow after tailings dam failure can provide a rational assessment of the inundation range and evaluate the subsequent disaster. Simultaneously, it can offer a foundation for tailings pond construction and safety management. This paper, focusing on a specific iron mine in Xiagao, Guangdong, establishes a three-dimensional simulation of the tailings pond based on the design drawings of the raised tailings pond. Utilizing the depth integral method as the theoretical basis, this research references parameter values obtained through model experiments for numerical simulation. Through the numerical simulation method, the study simulates the disaster range, flow, and spatial state of the tailings flow after a dam break. The tailings flow velocity and the depth of the flow in the affected areas are derived, demonstrating the disasters resulting from dam failure. Moreover, the feasibility of raising the tailings dam is evaluated. The assessment extends to the damage risk of tailings dam failure to critical downstream facilities and provides disaster prevention and control suggestions for high-risk situations. This study ultimately offers technical support for the prevention and control of tailings dam failure accidents and the advancement of mine safety production. Full article

Over the past few decades, a significant number of large concrete structures with deterioration problems related to the alkali–silica reaction (ASR) have been identified in Portugal and worldwide. Assessing the condition of ASR-affected concrete dams involves both diagnosis and prognosis. Diagnosis evaluates the structure’s current state, while prognosis predicts deterioration and safety implications. This is key to estimate the period during which the structure will effectively perform its function, and essential for the timely and cost-effective planning of the necessary mitigation, rehabilitation, and/or reconstruction works. This article aims to contribute to the ongoing discussion of this topic by the scientific and technical community and, therefore, presents the methodology adopted to assess the condition of a severely ASR-affected concrete dam in Portugal, the Alto Ceira dam, in which the concrete was produced with susceptible to ASR quartzitic aggregates and that was decommissioned and replaced by a new one in 2014. The article provides a brief review of the diagnosis and prognosis of the ASR in concrete dams, presents and analyses the results from laboratory testing (including chemical, microstructural, physical, mechanical, and expansion tests), in-situ testing, structural monitoring systems, visual inspections, and numerical modelling, aiming at assessing ASR impacts and evidencing the utility of the reported methodology on the appraisal of ASR-affected structures. Full article

The operation of large reservoirs significantly modifies flow–sediment regimes, and the reaches immediately downstream of the dams are the first to undergo responsive channel adjustments. Considering that the geomorphological responses are directly related to the flood control safety, channel stability and other sustainable functions of rivers, this paper explores the similarities and dissimilarities of the channel adjustments in the two reaches with gravel–sand beds immediately downstream of the Xiangjiaba reservoir and the Three Gorges Dam, respectively. The results show that major erosion primarily occurred during the initial years of reservoir impoundment. And then with the prominent reduction in washable sediment on the riverbed, the erosion intensity further weakened. It takes 6 to 13 years for the two reaches to reach a new state of relative equilibrium. In comparison, after the equilibrium state has been achieved, the reach with significant tributary sediment inflows exhibits alternating erosion and deposition dynamics, while the other remains relatively stable. The tributaries that transport a large amount of sediment during floods are the main sources of sediment deposition in the downstream reaches of the Xiangjiaba reservoir. However, the tributary inflow of the Qing River with low sediment concentrations has little impact on the riverbed evolution of the reaches from Yichang to Zhicheng immediately downstream of the Three Gorges Dam. These findings contribute to a deeper understanding of geomorphic adjustments near dams in response to upstream damming. Full article

Dam foundations are prone to leakage damage after being exposed to long-term water action, which seriously affects the operation safety of the dam. At present, concrete cut-off walls serve an important means of anti-seepage for dam foundations. However, due to construction challenges, the cut-off wall needs to be poured segment-by-segment during the construction process, and the joints between adjacent segments become weak parts for seepage prevention. Therefore, it is crucial to clarify the stress state of segmented discontinuous concrete cut-off walls. Based on the Lee-Fenves framework and the tension–compression constitutive relationship of fracture energy, a plastic damage calculation method was established in this paper to characterize the mechanical behavior of discontinuous cut-off walls. The method was then used to analyze the mechanical performance of discontinuous walls with segment joints containing slurry cake. The research results showed that compared to the continuous cut-off wall, the vertical settlement in the middle part of the discontinuous cut-off wall increased by 5.8%, and the displacement along the river flow direction decreased by 35.3%. As the wall segment width decreased, the joint opening and the degree of tensile damage were reduced accordingly, while the compressive damage in the middle and lower parts of the wall was intensified. As the wall depth decreased, the constraints and load on the bottom of the wall showed obvious changes, leading to a reduced stress and damage level of the wall. The findings provide reference for the design and safety control of cut-off walls. Full article

Nowadays, a detailed safety policy is applied for dams. These policies cover structural safety, monitoring, inspection, safe operation, and emergency plans. For high-risk dams, all these policy elements need to be included in dam safety programs. Deficiencies in embankment dams, which suffer the most damage, can be detected by visual inspection and programmed monitoring of dams. In dams, horizontal and vertical deformation, leakage, pressure, stress, loads acting on structural elements, and environmental factors are generally measured. These behaviors can be numerically modeled to determine the dam behavior. Numerical analysis methods are important for monitoring the safety of the dam. Models created with software such as Plaxis provide information about dam behavior. Although numerical analysis is very important for dams, obtaining the material parameters used in the construction of the dam needed for modeling, recording the construction stages of the dam, not taking the water level change in the dam reservoir instantaneously, and not taking the measurement records of the dam measurement instruments correctly for different reasons constitute problems and difficulties for the analyses. Within the scope of this study, İkizdere Dam in Turkey was modeled with the Plaxis finite element program; the survey and piezometer measurement data taken from the dam were evaluated by comparing with the analysis results; the difficulties and problems encountered in the modeling and analysis phase were stated, and recommendations were made on dam safety and numerical analysis. Thus, in addition to other studies, it was emphasized that it is important for dam engineers to monitor the use of numerical analysis models throughout the entire process, not only in the planning phase but also from the planning phase to the life of the dam, and to keep records of all recording intervals that will be needed in digital analysis models. Full article