Stability Of Dam Research Articles

Stability of the vajont dam

October 9, 1963: the wave of death hits Longarone, Pirago, Villanova, killing 1910 people in just four minutes. A huge mass of water passes the damming of the Vajont dam and devastates the valley below, a narrow gorge that cuts through Mount Toc which is located on the border between the Italian regions of Veneto and Friuli-Venezia Giulia.

SEEPAGE AND SLOPE STABILITY ANALYSIS FOR SAFETY EVALUATION OF PIDEKSO DAM

The Pidekso Dam is one of the National Strategic Projects. The dam is located in Pidekso Village, Giriwoyo District, Wonogiri Regency, Central Java Province. The dam was designed as an earth-fill dam of zonal type with random fill and an upright core. Although the construction of a dam provides huge benefits, it may pose a potential hazard if collapses. Therefore, it is necessary to conduct a study to determine the safety of the Pidekso Dam in various conditions, including during an earthquake occurrence. The study analyzed the seepage on the main dam construction using Seep/W and dam-slope stability using Slope/W by reviewing the cross-section of the dam body and its foundation. The data used as the input in the analysis include the coefficient of soil permeability, soil cohesion, internal friction angle, and soil density based on field investigations and laboratory analysis. For the seepage analysis, manual calculations were also carried out using the Schaffernak and Casagrande method compared to the Seep/W results. From the results of the seepage analysis with Seep/W, the Pidekso Dam is safe against leakage with the largest discharge of 6.480×10 -4 m 3 /s at maximum water level. The safety factor against piping showed safe results with the lowest safety factor of 6.295 at the end of the filter drainage. In the dam stability analysis with Slope/W, several unsafe conditions have the lowest safety factor of 0.926 on the upstream slope at the minimum water level with MDE (Maximum Design Earthquake) of 0.25. In Makdisi-Seed analysis, the highest slope displacement value is 0.862 m with an earthquake magnitude of 8.25; Y/H (Y is the depth from the top of the dam and H is dam height) of 0.25. This value is smaller than the maximum limit of 2.00 m, hence the dam is still in a safe condition.

DESIGNING OF CONTINUOUS DAM MONITORING USING GLOBAL NAVIGATION SATELLITE SYSTEMS

<jats:p>The paper presents the procedure for designing a geodetic system for continuous dam monitoring and equipment necessary for the application of the Global Navigation Satellite System (GNSS). It also points out the conditions that must be respected when choosing the position of the network points and indicates the advantages and disadvantages of this system in relation to systems based on terrestrial methods. Basically, both systems provide the data necessary to monitor dam stability. Theoretical considerations have been applied to monitoring system of Soubella earth-filled dam, in Algeria. The dam created an artificial lake with a capacity of 160,000,000 m3, providing water for irrigation in the settlement below the dam. Due to the settlement vicinity, it is planned to carry out continuous dam monitoring.</jats:p>

Seepage Patterns in an Earth-Rock Fill Dam Evaluation using Electrical Resistivity Tomography (ERT) Method

Seepages in the earth-rock fill dam are usually monitored by pore pressure, seepage water table, and seepage discharge. However, those monitoring are difficult to describe the seepage patterns because they are installed only in certain points. This research evaluated the seepage pattern resulting from Electrical Resistivity Tomography (ERT). The resistivity was measured by installing electrodes upstream of the Dam at every 10 m and downstream at 20 m distances. The seepage pattern was analysed from the resistivity 2 Dimension distribution using the RES2DINV program. The results showed that the seepage pattern resulting from the ERT method’s resistivity data, which was compared with data of surface dam deformation, pore pressure, and seepage water table, could explain the seepage discharge data. Based on those confirming data, the resistivity data of the ERT method was appropriate to explain the seepage pattern in the earth-rock fill dam and can be further utilized for dam stability analysis.

Dynamic behaviour and failure mechanism of coal subjected to coupled water-static-dynamic loads

The stability of a coal pillar dam in a coal mine underground reservoir is affected by water pressure, static geo-stress, and coal mine earthquakes. Thus, it is essential to accurately evaluate the dynamic behaviour of coal under coupled water-static-dynamic loads to reasonably design a coal pillar dam. In this study, an innovative test system was developed based on a split Hopkinson pressure bar (SHPB) device, and a series of impact tests of coal under the coupled action of impact load, static axial preloading, and water pressure were performed with this system. The effects of coupled water-static-dynamic loads on mechanical behaviours, including strength and deformation characteristics, failure mode, and energy dissipation of the coal samples were systematically investigated. Results showed that the dynamic deformation process of the coal samples can be divided into three stages: linear elastic deformation stage, crack unstable propagation stage, and post-peak failure stage. Impact and higher axial static loads were the two negative factors that made the coal samples more prone to damage. In contrast, the presence of water pressure positively affected the sample, which improved the dynamic strength and reduced the failure strain of the sample. Energy dissipation characteristics showed that water pressure enhanced the energy utilisation efficiency of the sample. Furthermore, the microcosmic mechanism of free water protecting coal from the fractures was also examined.

Safety Evaluation of Arch Dam Subjected to Underwater Contact Explosion

The stability of an arch dam can be significantly damaged by an extreme underwater explosion. This study proposed a damage index for assessing the degree of local damage of an arch dam after the dam was subjected to an underwater explosion. The damage index was applied to assess local damage at the middle part of the dam, surcharge holes, and abutment. A model was developed to evaluate the stability of the entire dam based on the spatial distribution of damage and the damage on the base interface. Results showed that local explosion damage at flood discharge holes or abutments might cause instability of the arch dam. When the contact explosion action location is on the abutment, it only needs 310 kg to cause the overall damage of the arch dam, while when the action location is on the middle part of the dam, the quantity of explosive required is 2800 kg.

Exploration and Research on the Propagation Law of Seepage Risk Network in Tailings Storage Facility

The seepage accident of a tailings pond poses a serious threat to the stability of tailings dams and the surrounding environment. To reduce the occurrence of seepage accidents, this paper studies the identification of seepage hazards, the propagation law of seepage risk, the importance of hazards, and the priority of hazard treatment. To overcome the subjectivity and omission of hazard identification, according to the complexity and dynamics of tailings seepage, this paper proposes the evidence-based identification method of three-dimensional seepage hazards (EIMTSH) to identify the hazards of the tailings seepage system and the relationship between hazards. Then, on the basis of identifying the hazards of the tailings seepage system, the propagation network of seepage risk in tailing ponds (PNSRTP) is constructed based on the complex network theory. By analyzing the characteristics of the PNSRTP, it can be found that the propagation of seepage risk is scale-free and small-world. Through the node deletion method, this paper finds that the nodes with a higher degree value can reduce the network efficiency more quickly and should be governed first. By giving priority to the treatment of hazards with higher degree, the propagation of seepage risk can be reduced more quickly and the risk management level of tailings ponds can be improved, which is helpful to realize the sustainable development of mining production.

DYNAMIC RESPONSE AND STABILITY ANALYSES OF AKOSOMBO DAM USING NUMERICAL ANALYSIS

Dams are very important in Ghanas economic development and environmental improvement. Although Ghana dams are seismically far from the active zone, accurately analysed dams should be evaluated since failure could severely impact the people in the flood environment and the regions economy on a large scale. This paper proposes a numerical procedure for the static, slope stability, and dynamic analysis of the Akosombo embankment dam. Nineteen horizontal acceleration time histories recorded data was used based on Maximum Design Earthquake (MDE), Maximum Credible Earthquake (MCE), Design Basis Earthquake (DBE) and Operating Basis Earthquake (OBE) data. The numerical results estimated showed that the Akosombo embankment dam is likely to experience moderate deformations during the different design earthquakes. The result also indicated that non-linear analysis capable of capturing dominant non-linear mechanisms could be used to assess the stability of embankment dams. The factor of safety (FS) calculated was greater than 1.5 for high reservoir, rapid drawdown condition and low reservoir condition whereas, the FS values were found to be 1.42 for slow drawdown condition.

Validation of computational liquefaction for tailings: Tar Island slump

Finite-element analyses using critical state theory proved necessary to understand the development of static liquefaction during three recent large tailing dam failures at Fundao (in Brazil), Cadia (in Australia) and Brumadinho (in Brazil). However, the complexity of these events prevents these analyses being viewed as a complete validation of the methodology. Here the authors evaluate a far simpler case of static liquefaction: the 1974 Tar Island slump (in Canada). This upstream slump involved a rapid drop of 5 m during construction of a 12.5 m high upstream raise over loose tailings. While not a dam stability issue, the event has the attraction for validation of being load-induced, with simple geometry, and with known material properties and in situ state. The computed liquefaction develops from a prior drained condition before propagating rapidly undrained – there are similarities to the video record at Brumadinho (an animation is provided as online supplementary material to illustrate this). A range of scenarios are explored, with the base case of taking reported conditions at face value giving deformations close to those measured. An important aspect was using elastic shear moduli determined by geophysical methods. The analyses were carried out with commercial software (Plaxis) and used critical state theory with largely familiar soil properties measured by standard methods.

Preliminary Risk Assessment of Dam Failure at the Location of the Cukaru Peki Deposit, Bor (Serbia)

Industrial waste landfills, as evidenced by frequent accidents occurring in recent years, are regarded as one of the most hazardous facilities in the world. For the adequate management of a landfill, risk assessments of dam failures should be performed before operations begin. This paper deals with the preliminary risk assessment used for the tailings and pyrite concentrate storage facilities, as well as the drainage waters reservoir, which are currently at the development and construction stage in the Cukaru Peki deposit located in eastern Serbia. The research was conducted to establish the facts and level of risk at an early stage to allow for timely prevention of potential accidents and bring operational practice in line with design requirements. The annual failure probability was estimated using a semi-empirical method, based on the dam stability factor. While, the framework proposed by the New Zealand Society on Large Dams was applied to assess the consequences of potential failures. The risk was assessed as a function of accident probability and the severity of possible consequences, and a 7 × 7 risk matrix was applied for analysis and evaluation. The level of dam failure risk at the location of the Cukaru Peki deposit was preliminarily assessed as moderate and conditionally tolerable, based on a low estimated probability of accident and a significant severity of consequences. Once the operation of these facilities starts risk assessments should be regularly updated, in order to maintain this level, and in accordance with the current situation, the modelling of specific accident scenarios should be included.

The Effects of Internal Erosion on the Physical and Mechanical Properties of Tailings under Heavy Rainfall Infiltration

The stability of tailings dam will be affected by the internal erosion under unsteady seepage caused by heavy rainfall infiltration which changes the physical and mechanical properties of tailings. In this paper, the hydraulic sedimentary model was established to investigate the effects of dry beach slope on the sedimentary characteristics of tailings in upstream tailings dam, and the results indicated that the dry beach with a larger slope has a more obvious stratification of tailings. Additionally, the sand column model was built to investigate the effects of internal erosion on the physical and mechanical properties of sedimentary tailings under unsteady seepage, and the results indicated that the migration of fine-grained tailings was caused by internal erosion increases the permeability and reduces the shear strength of the tailings. After internal erosion of tailings under heavy rainfall in 50 years return period for 24 h, the average particle size of downstream tailings (sample DT), midstream tailings (sample MT), and upstream tailings (sample UT) increased by 6.4%, 12.0%, and 2.4%, respectively, the hydraulic conductivity of the samples DT, MT, and UT increased by 27.2%, 17.9%, and 15.3%, respectively, and the shear strength of each samples decreased by 20.9%, 15.1%, and 12.4%, respectively.

Numerical simulation of concrete face rockfill dam seepage: case study of Miaojiaba dam, China

Concrete face rockfill dams are widely used in hydropower engineering because of their many advantages. As important structures, if the performance of the concrete face slab and the impervious curtain is weakened, leakages and even serious dam failures can occur. Based on an equivalent quasi-continuum medium model, three-dimensional finite-element numerical simulations of the seepage behaviour of Miaojiaba dam, China, are performed. The seepage field and seepage characteristics, including the phreatic line, maximum hydraulic gradient and seepage discharge, are analysed quantitatively and systematically under various abnormal conditions. The results show that cracks in different areas of the face slab and different degrees of degradation in the impervious curtain influence the seepage field in different ways, with cracks in the lower face slab being the most serious. Ensuring that the face slab and impervious curtain are working as intended is very important for the integrity of the dam. Therefore, the design and construction quality of impervious structures should be strictly controlled. Under abnormal conditions, seepage control should be realised to ensure the safety and stability of concrete face rockfill dams.

Influence of dam geometry on the breaching process of landslide dams

The breaching process of landslide dams is influenced by many factors. In this study, several laboratory experiments on the overtopping of landslide dam were conducted to investigate the specific effects of dam geometry on the breaching process of landslide dams. According to the test results, geometric parameters of the dam, including dam height, crest width, and downstream slope, had considerable effects on the breaching process. The breaching process was divided into three stages: (1) breach initiation stage, (2) breach development stage, and (3) attenuating and reequilibrium stage. Dam height reflected the volume of impoundment and affected the breach development stage. With the increase of the dam height, the peak discharge increased, and its time of arrival was delayed. The dam crest width affected the breach initiation stage. The peak discharge increased significantly, and its arrival time was shortened by the decrease in the dam crest width. Downstream slope reflected the dam stability and affected the breach initiation and breach development stages. With the decrease of the downstream slope, the peak discharge decreased, and its time of arrival was delayed considerably.

Hazard Prediction Method of Landslide Damming and Analysis of a Typical Application

Landslide damming occurs frequently, affects a wide range of areas, and is difficult to predict, thus threatening the safety of human life, properties, and engineering structures. However, the studies on early identification remain at an early stage. This paper proposes a hazard prediction method for landslide damming, which includes prediction models of river blockage, landslide dam geometry, landslide dam stability, and dam breach time. On this basis, the landslide damming hazard can be predicted via ten parameters: the repose angle of the landslide mass, the landslide volume, the landslide discharge, the river discharge, the reservoir capacity of the barrier lake, the bottom width of the valley, two slope angles on both sides of the valley, the valley bed inclination, and the sliding surface dip-angle. The proposed method was examined in relation to a typical case, namely, the Baige landslide damming that occurred in 2018 in China, with the application process presented integrally. The results indicated that the river blockage model predicted that the Baige landslide could form a huge landslide dam, which was fully in line with the actual situation. The landslide dam geometry model provided the predicted value of the height, width, and length, as well as the downstream and upstream angles, of the Baige landslide dam, with the maximum relative error between the predicted values and the true values less than 20%. The prediction results of the landslide dam stability model indicated that when the reservoir capacity of the barrier lake is 280 million m3, the dam could breach. In fact, the dam breach time model predicted that the dam could breach within 38 h after the landslide dam formation, which was 11% less than the actual breach time of the Baige landslide dam. The current study provides a useful theoretical reference and technical support for the early identification, prediction, and warning of the disaster chain of landslide-induced river blocking.

Toe drain size and slope stability of homogeneous embankment dam under rapid drawdown

The slope stability of an embankment dam has been always a serious concern of any design team. Unfortunately, the information on the potential influence of a toe drain size on the slope stability of an embankment dam under rapid drawdown conditions is still scarce. This study investigated the potential effect of a toe drain size on the slope stability of a homogeneous embankment dam under rapid drawdown conditions. Three different sizes (5m, 10m, and 15m) of the toe drain were investigated under instantaneous (worst scenario) and 5 days (more realistic) drawdown rates with the help of numerical modeling in GeoStudio. From the results, it was observed that the pore-water pressures at the upstream face of the embankment decreased with the increase in the toe drain size, while the pore-water pressures at the downstream toe were increasing with the increase in the toe drain size. The factor of safety values were also observed to be affected by the changes in the toe drain size.

Integrated Treatment of Mining Dam Wastewater with Quaternized Chitosan and PAN/HPMC/AgNo3 Nanostructured Hydrophylic Membranes

This study was developed a novel nanostructured membrane by electrospinning process, from polyacrylonitrile (PAN) modify by hydroxypropyl methylcellulose (HPMC) polymers containing silver nitrite (AgNO3), to be used as a filter in an integrated wastewater dam treatment process to reuse it as drinking water. Different formulations (108 samples) were electrospun from PAN and (0, 5, 10 w%) HPMC and (0, 0.5, 1 w%) solutions to selected a more efficient formulation in water disinfection and higher hydrophilic character of the membrane to flow performance in the wastewater treatment. The PAN and HPMC phases in membranes were characterize by infrared spectroscopy and thermogravimetric analysis. The nanostructured membranes were characterized by Scanning electron microscopy and the fibers had a diameter between 251 ± 58 and 306 ± 49 nm. The presence of HPMC and AgNO3 in membrane formulation endows superhydrophilicity and permeability increase which up to 21,151 ± 445 L⋅m−2 Permeability h−1. After filtration process with PAN/HPMC/AgNO3, all the tested water potability indexes were achieved. The primary treatment, using quaternized chitosan reduced the turbidity parameter from 19,000 Nephelometric turbidity units (NTU) to 14 NTU, and after filtration with nanostructured membrane, to levels was below 1 NTU and pathogenic potential removed (Total Coliform and Escherichia coli). The results of this study indicated that the hydrophilic nanostructured membranes PAN/10% HPMC/1% AgNO3 have adequate properties to potential wastewater treatment mining for reuse. It’s give a sustainable strategy for managing wastewater which should be reduce the volume of water in the tailing’s dams and contributes to increasing the stability of dams and reducing risks with catastrophic environmental impact.

INVESTIGATING THE EFFECT OF LONGITUDINAL GALLERY ON DYNAMICAL RESPONSE OF GRAVITY CONCRETE DAMS USING FEM

This research aimed to consider the necessity of studying different dimensions of existing galleries in gravity concreted dams regarding design limitations and the dam sustainability provision. In recent years, structural optimization has been studied extensively with various considerations. Concrete volume in concrete dams is higher than in other concrete dams. Therefore, if the concrete volume of these dams can be reduced without reducing the dam safety and stability, the costs of constructing such dams could be significantly reduced. For this purpose, in this paper, the Pine Flat Gravity Dam has been selected, its numerical model has been constructed and stimulated under the Taft earthquake. There are three types of small, medium, and large size galleries in different positions. The dam reservoir and foundation in the current study have been modeled, and the foundation has been assumed to have no mass. Then the results have been examined. The innovation of this research is in identifying the most optimal shape and position of the gallery in the body of the weighted concrete dam, which is based on stress and strain responses. It can be concluded that while the medium gallery was in the middle of the dam, the optimum condition for reducing concrete was achieved by maintaining the dam stability.

Comprehensive Assessment of the Effect of Water Pressure on the Development of Cracks in Gravity Concrete Dams

In recent years, extensive studies have been conducted to ensure the safety and stability of concrete dams. The development of numerical methods in considering more factors affecting the response of dams and also increasing the accuracy of calculation methods has played an important role in ensuring the safety of concrete dams. Therefore, one of the most important points in the design and analysis of concrete dams is to predict the location of cracks, expand it, investigate the phenomenon of hydraulic failure, consider the pressure caused by the infiltration of reservoir water into cracks and joints in static and dynamic states, and find solutions prevention of dam destruction due to this phenomenon. In the study of the effect of tensile strength, with increasing tensile strength, the reservoir water level increases at the beginning of cracking and the final reservoir water level increases, but there is no linear relationship between tensile strength and the two responses. In general, in examining the refractive energy parameter in each of the states with and without taking into account the water pressure inside the crack, the results of the mentioned models are slightly different from each other, but comparing the results shows that in nonlinear analysis considering water pressure inside the crack failure energy change has a greater impact on the results of these models.

Tailings desiccation process studied in environmental chamber experiment

Case studies and numerical simulations show that the long-term stability of tailings dams largely depends on the evolution of their water content. Therefore, desiccation is one of the critical processes influencing the tailing dam's safety. In this work, the air-drying of tailings, starting from a sludge condition, is studied using a fully instrumented column experiment, performed in an environmental chamber with temperature and relative humidity control. Based on the experimental observations, a conceptual model for the desiccation process is proposed. The model consists of the combination of two mechanisms driven by evaporation: shrinkage and capillary rise. The latter is only activated after a granular structure develops (shielding skeleton), capable of sustaining the suction-induced intergranular forces. This evidence explains the tendency of real deposits to develop an unsaturated, dry tailings crust enclosing a body of mud-consistency tailings. In addition, the role of dissolved salts in the desiccation process was observed. Solutes in pore water limit the evaporation rate throughout the test by increasing osmotic suction. Moreover, salt precipitation was observed to cause an interruption of the desiccation process on two occasions during the experiment: first, by the formation of a superficial precipitation crust and later by pore clogging within a shallow layer.

Multifield Coupling Numerical Simulation of the Seepage and Stability of Embankment Dams on Deep Overburden Layers

Multifield Coupling Numerical Simulation of the Seepage and Stability of Embankment Dams on Deep Overburden Layers