Dam Slope Research Articles

Seepage and Pore Pressure in the Core of a Earth-and-Rockfill Dam

A numerical solution to the anisotropic seepage problem for an earth dam is examined. Results are presented for solution of the problem and analysis of the stability of an earth dam slope with due regard for the influence seepage anisotropy.

Deformation-based safety monitoring model for high slope in hydropower project

Because of the outstanding issue of high slope stability in hydropower project, the statistical slope stability analysis is studied by applying deformation monitoring data based on the probability and catastrophe theory. According to the analysis of geological conditions and measured information of high slope, the mechanical slope stability analysis is established. The EMD (empirical mode decomposition) method is introduced, which is used to fitting parameters and solving the aging component of slope deformation by breaking through the traditional regression model, and a method to abstract stationary and nonlinear aging component is proposed eventually. Combining with the theory of catastrophe, a cusp catastrophe model of slope stability is established. The early warning indexes of slope stability are put forward in terms of the deformation acceleration. Applying these above methods, the stability of the spillway high slope of a certain concrete face rockfill dam during operation period is analyzed and evaluated.

하천제방의 제내지 비탈면의 훼손에 따른 영향성 평가

하천제방의 제내지 비탈면의 훼손에 따른 영향성 평가

A study of turbulent flow in large-scale porous media at high Reynolds numbers. Part I: numerical validation

ABSTRACTAnalyses of turbulent flows through the downstream slopes of embankment dams are important for dam safety assessments, especially considering high-risk scenarios such as a sudden release of water due to internal erosion. Flow prediction is difficult in such situations due to coarseness of construction materials and high Reynolds numbers. The present study addresses this issue through comprehensive numerical modelling. The novelty of the proposed approach lies in a combination of large-scale experiments and three-dimensional numerical simulations, leading to a fully calibrated and validated model that is applicable to flows through cobble-sized materials (100–160 mm in diameter) at high Reynolds numbers (>104). Comparing the results of the standard turbulence models to data from the large-sale experiments, the renormalization group theory-based model yielded the smallest relative errors based on the hydraulic gradients. Considering the flow field, the turbulent shear stress increased by a factor of 17, and the time-averaged vorticities intensified by factors of 2, 6 and 10 for vorticities in the x-, y- and z-directions, respectively, due to the presence of cobbles.

Computation of Seepage through Homogenous Earth Dams with Horizontal Toe Drain

This investigation concerns to find a new equation for computing the quantity of seepage through homogenous earth dam with horizontal toe drain. For this purpose the computer program SEEP/W (which is a sub-program of Geo-Studio) was used. The SEEP/W runs were carried out with three different downstream slopes of the dam, three different upstream slopes, three variable horizontal toe drain lengths, three different free boards, three different top widths and three different heights of the dam. For each run the quantity of seepage was determined. The results show that the seepage discharge increased with increasing upstream slope, downstream slope, upstream reservoir water depth and length of horizontal toe drain. Also, the results show that the seepage discharges decreased with increasing the top width of the dam and the height of the free board. Using SEEP/W results with helping a dimensional analysis theory, a new easy and reliable empirical equation for computing seepage discharge through homogenous earth dams with horizontal toe drain was developed. The analysis of the results by Artificial Neural Network (ANN) shows that the length of horizontal toe drain (L) is the more geometrical variable effect on the seepage discharge, while the upstream slope (tanθ) of the earth dam has a little effect.

Taludes de barragem: análises determinísticas e probabilísticas – estudo de caso

Atualmente, as análises determinísticas são utilizadas com grande frequência para a obtenção de um fator de segurança de taludes, apresentando todavia limitações na consideração das incertezas associadas à variabilidade dos parâmetros de resistência dos materiais. As análises probabilísticas permitem resolver este problema, porém, são pouco difundidas no meio técnico. Assim, apresenta-se neste trabalho comparações entre análises determinísticas, pelos métodos de Bishop simplificado e Spencer, e probabilísticas, pelo Método de Monte Carlo, através do estudo de caso de uma barragem utilizando o software Slope/W da GeoStudio. Também são feitas comparações com os critérios estabelecidos pela Eletrobrás e pelo USACE. Verificou-se que a barragem possui seus fatores de segurança dentro dos limites estabelecidos por ambos os critérios. Verificou-se ainda a facilidade de utilização do método probabilístico, desde que existam dados suficientes disponíveis para as análises.

Design Optimization of a Concrete Face Rock-Fill Dam by Using Genetic Algorithm

This paper combined with the adaptive principle to improve the genetic algorithms (GA) and applied it to optimal design of the shape of the concrete face rock-fill dam (CFRD). Based on the improved GA, a mathematical model was established for the design optimization of CFRD. CFRD utilizes dam cost as objective function and dam slope and geometries of the dam material partition as design variables. Dam stability, stress, displacement, and stress level are used as the main condition constraints. The calculation procedures were prepared, and the GA was used to optimize the design of Jishixia CFRD. Results show that the GA could solve the global optimal solution problem of complex optimization design, such as the high degree of nonlinearity and the recessiveness of constraint conditions, and using the GA to optimize the CFRD design can reduce the quantities of projects and engineering safety costs.

ASSESSMENT OF RELIABILITY AND RISK DEGREE FOR ACCIDENT INITIATION AT SLIME STORAGES OF 4th MINING ADMINISTRATION, JSC “BELARUSKALI”

Definition of reliability for dams of slime storage embankment is given on the basis of reliability theory and characteristics of reliability and their analysis are presented in the paper. The paper specifies qualitative indices for earth dams which are subdivided in two groups: applicability factors and structural reliability factors. A short analysis of all possible causes for accident initiation at earth dams has been made and the analysis has permitted to pinpoint eleven main objects for diagnosis for slime storage dams. In order to assess risk degree of accident initiation at JSC “Belaruskali” slime storages all possible causes of emergency cases and their probability of occurrence have been analyzed in the paper. The paper acknowledges the fact that dam malfunction is possible, as a rule, due to violation of operational rules and regulations. Main parameters of slime storage state which are to be controlled regularly in the process of its operation have been noted in the paper. Observation results over slime storages, calculations of dam slope stability for normal operation (a principal calculation case) and operating irregularities in water seals (a special calculation case). As a stability margin factor is close to 1.0 for a special calculation case, an extreme position of depression curve has been determined for all design sections. It has been recommended to carry out a constant control over its position, and in the case when it reaches its peak value it is necessary to undertake appropriate measures in order to reduce its value. Final expert estimations on probability of accident initiation at the investigated slime storage dams of the 4th Mining Administration, JSC “Belaruskali” have been prepared on the basis of the analysis comprising all the required factors. A conclusion has been made about low risk degree of their destruction.

Earthquake-induced slope failure susceptibility in eastern Nepal

Nepal is considered as one of the earthquake-prone countries in the region. Earthquake is a major concern of Nepal because of rapid population growth, poor land use planning, precarious settlement patterns, and poorly implemented building code. Earthquakes in Nepal have been reported since 1255 while major earthquakes were recorded in 1408, 1681, 1810, 1833, and 1866, 1934, 1980, 1988, 2011, and 2015. An earthquake in September 18, 2011 measuring 6.9 in Richter scale, killed 6 people and injured 30 people in Nepal. There were many roadside slope damages near the epicenter area. To assess the roadside slope damages after this earthquake, a field visit was conducted and a landslide inventory map along the roadside slope was prepared for most damaged area. This paper provides a comprehensive information about earthquake-induced slope failures occurred in the Mechi Highway of eastern Nepal and also discusses an approach of earthquake-induced slope failures hazard mapping in Nepal.

Physical Model Test Study of the Relationship Between Loess Landslide and Rainfall

Launching research has important theoretical and practical value on model test study of the relationship between loess landslide and rainfall. According to the monitoring data of model test of loess slope, formula expression of safety factor has been fitted on landslide. Firstly, the loess slope damage process was monitored at different rainfall intensity, rainfall duration through rainfall landslide model tests. Secondly, some parameters were determined by laboratory tests, such as loess unit weight, moisture content, shear strength. Thirdly, the relational expression was fitted between moisture and rainfall intensity, rainfall duration, cohesion, internal friction angle, unit weight. Finally, moisture content being an intermediate variable, the expression was got between landslide safety factor and rainfall intensity, rainfall duration.

Geochemical assessment of mine waste cover performance post reclamation at Parc mine, North Wales

Parc mine in north Wales was abandoned after closure in 1963 and spoil heaps were left to erode into the Nant Gwydyr and Conwy River. A storm event in 1964 caused the west slope of the tailings dam to collapse into the river, polluting 11 ha of farmland with lead and zinc. Reclamation work commenced in 1978 and involved reshaping the tailings pile and capping the north and central sections of the site with limestone quarry waste. The north section was also sown with metal-tolerant vegetation ( Festuca rubra, Argostis tenuis and Trifolium repens ). The aim of the study was to understand how different reclamation surfaces affected soil chemistry using GIS. The uncapped south section, whilst having the most heavily polluted soil (74 mg/kg As, 24,000 mg/kg Pb, and 19,000 mg/kg Zn), supported the establishment of patchy but diverse metal-tolerant vegetation ( Alnus incana, Fagus sylvatica, Ulex, Sorbus aucuparia) . The capped north section had the least polluted soil (19 mg/kg As, 478 mg/kg Pb, and 1400 mg/kg Zn), densely vegetated with a nitrogen-fixing legume ( Trifolium repens ), and was able to support grazing animals, but remained visually incongruous and failed to support the re-establishment of native vegetation. The central section, which combined capping with native vegetation ( Betula pubescens and Quercus petraea ), was considered moderately polluted (26 mg/kg As, 3908 mg/kg Pb, and 9000 mg/kg Zn). Zinc was found to be the limiting contaminant for vegetation growth with soil concentrations exceeding 12 000 mg/kg corresponding to areas of bare ground in the south and central sections. Barium was the only element to increase in the capped sections, indicating the limestone quarry waste used to cap the tailings was most likely barium-rich.

The possible role of brittle rock fracture in the 1963 Vajont Slide, Italy

We use a state-of-the-art numerical simulation approach to investigate the Vajont slope failure, a large catastrophic landslide that resulted in the loss of 1910 lives. This study represents the first three-dimensional (3D) brittle fracture simulation of the Vajont Slide that includes the effect of groundwater on the failure process. A realistic representation of the Vajont slope geometry, failure surface and discontinuities in a 3D lattice spring code allowed us to study the kinematics of the landslide. Using a lattice-spring block model approach, the relations among the number of blocks, slope damage, and stability are investigated. The influence of an elevated groundwater table on displacements and cracking within the model is evaluated. The results show a good agreement with the reported microseismic events prior to the failure. Two new techniques, “damage intensity”, D32, and the “ellipsoid of damage”, are introduced and used to quantify brittle damage within the numerical simulations.

Microseismic monitoring and numerical simulation on the stability of high-steep rock slopes in hydropower engineering

For high-steep slopes in hydropower engineering, damage can be induced or accumulated due to a series of human or natural activities, including excavation, dam construction, earthquake, rainstorm, rapid rise or drop of water level in the service lifetime of slopes. According to the concept that the progressive damage (microseismicity) of rock slope is the essence of the precursor of slope instability, a microseismic monitoring system for high-steep rock slopes is established. Positioning accuracy of the monitoring system is tested by fixed-position blasting method. Based on waveform and cluster analyses of microseismic events recorded during test, the tempo-spatial distribution of microseismic events is analyzed. The deformation zone in the deep rock masses induced by the microseismic events is preliminarily delimited. Based on the physical information measured by in situ microseismic monitoring, an evaluation method for the dynamic stability of rock slopes is proposed and preliminarily implemented by combining microseismic monitoring and numerical modeling. Based on the rock mass damage model obtained by back analysis of microseismic information, the rock mass elements within the microseismic damage zone are automatically searched by finite element program. Then the stiffness and strength reductions are performed on these damaged elements accordingly. Attempts are made to establish the correlation between microseismic event, strength deterioration and slope dynamic instability, so as to quantitatively evaluate the dynamic stability of slope. The case studies about two practical slopes indicate that the proposed method can reflect the factor of safety of rock slope more objectively. Numerical analysis can help to understand the characteristics and modes of the monitored microseismic events in rock slopes. Microseismic monitoring data and simulation results can be used to mutually modify the sensitive rock parameters and calibrate the model. Combination of microseismic monitoring and numerical simulation provides a more objective basis for the numerical model and parameters and a solid mechanical foundation for the microseismic monitoring.

Research on shape optimization of CSG dams

The multi-objective optimization method was used for shape optimization of cement sand and gravel (CSG) dams in this study. The economic efficiency, the sensitivities of maximum horizontal displacement and maximum settlement of the dam to water level changes, the overall stability, and the overall strength security were taken into account during the optimization process. Three weight coefficient selection schemes were adopted to conduct shape optimization of a dam, and the case studies lead to the conclusion that both the upstream and downstream dam slope ratios for the optimal cross-section equal 1:0.7, which is consistent with the empirically observed range of 1:0.6 to 1:0.8 for the upstream and downstream dam slope ratios of CSG dams. Therefore, the present study is of certain reference value for designing CSG dams.

Effect of seismic permanent deformation on safety and stability of earth-rock dam slope

In order to study the effect of seismic permanent deformation on the safety and stability of earth-rock dam, the permanent deformation is considered as the non-design permanent load, and the stress-strain hysteresis curve is also considered when the earth is under cyclic load. The research work can make the calculation results of plastic collapse more accurate by including the effect of the post-earthquake degree of plastic deformation on the stability of the earth-rock dam, and the dam safety factor decreases from 2.50 to 1.90 after the magnitude-8 earthquake. Moreover, the research work will also improve the design of the earth-rock dam under abnormal operating conditions.

댐 비상방류 설계기준 선정을 위한 수리수문학적 검토(I)

It is well known that emergency outlet works have to be provided for the safety of dams. However, concept of emergency outlet works did not applied for the design of the most dams in Korea. Korean design standard for low-level outlet works does not provide enough design criteria which could be used in design of emergency outlet works. In this research, as-built status and hydraulic design criteria of outlet works, such as drawdown rate or hydraulic pressure due to the impounded water depth, were examined. Another relationship between drawdown rate and the dam slope stability was also examined with SEEP model. It was found that 25% reduction of impounded water depth decreases the pressure forces about 50%. Therefore, outlet works should be designed to drawdown properly at the beginning of the emergency. Seepage analysis of dam bodies showed that most of Korean dams could safely stand for 1m/day drawdown rate. Higher drawdown rate could result high discharge so the drawdown rate must be related with the flood risk of downstream. Finally, multi-stage design was recommended that faster discharge for the initial 25% of water depth in 7-10 days than the rest of it in 1-2 months.

댐 비상방류 설계기준 선정을 위한 수리수문학적 검토(II)

It is well known that emergency outlet works have to be provided for the safety of dams. However, concept of emergency outlet works did not applied for the design of the most dams in Korea. Korean design standard for low-level outlet works does not provide enough design criteria which could be used in design of emergency outlet works. In this research, as-built status and hydraulic design criteria of outlet works, such as drawdown rate or hydraulic pressure due to the impounded water depth, were examined. Another relationship between drawdown rate and the dam slope stability was also examined with SEEP model. It was found that 25% reduction of impounded water depth decreases the pressure forces about 50%. Therefore, outlet works should be designed to drawdown properly at the beginning of the emergency. Seepage analysis of dam bodies showed that most of Korean dams could safely stand for 1m/day drawdown rate. Higher drawdown rate could result high discharge so the drawdown rate must be related with the flood risk of downstream. Finally, multi-stage design was recommended that faster discharge for the initial 25% of water depth in 7-10 days than the rest of it in 1-2 months.

Stability Analysis of Dam Slope by Double Safety Factors of Dynamic Local Strength Reduction Method

When calculating the dam slope failure process, traditional strength reduction method doesn't consider the difference of decay rate between cohesion and internal friction angle and discount the strength parameters for all elements. This paper uses two different reduction factors for material strength parameters, slope cohesion and internal friction angle. Based on the yield approach index criterion, we change the reduction region in time and put forward a double safety factor of dynamic local strength reduction method for engineering analysis of dam slope stability.

Impact of Geotechnical Factors on the Safety of Low Embankment Dams From the Perspective of Technical and Safety Supervision

Abstract Our research deals with a broad spectrum of problems concerning the variability of geotechnical factors and their influence on the safety of the biggest group of dam constructions in Slovakia, i.e., low earthfill dams. Its specific aim is the observation of their risk factors by using our experience and knowledge gained while working in the sector of technical and safety supervision. To achieve the aims of a research thesis, we analyzed 39 low earthfill dams. We performed observations and documented their conditions with the aim of clarifying the risk factors. After an analysis of the information materials that characterize dams and after a statistical analysis of the measurement results in situ, including measurements from technical and safety supervision databases, we performed an analysis by using mathematical modeling to evaluate the safety of the dam constructions. Out of the total number of 39 dam constructions, an analysis of the stability of the dam slopes was performed on 37 dams, and deformation problems were analyzed on 28 of the dams. Filtration problems were analyzed at 26 dams, and a complete evaluation of the intensity of filtration movements was performed on 19 of the constructions. On the basis of a detailed analysis of the 39 dam constructions, we specified their problems and the concomitant consequences of the problems. Geotechnical risk factors and specific risks that determine the safety of water constructions were characterized. The analysis confirmed the importance of an engineer-geological and geotechnical checkup in the process of preparation and building (alternatively, during reconstructions and sanitation work) of such water constructions and also the importance of monitoring in the process of dam usage. Technical and safety checkups were also shown to be important when analyzing risk factors. The conclusions of the knowledge gained and the recommendations for the practice deal with recommendations to change the flow policy, develop a central project register, and develop documents and databases that are needed for analyses of the safety of low earthfill dam constructions in the Slovak Republic.

Analysis on Seismic Response Spectrum of Different Slope Ratio Dam

The actual tailings dam as an object, analyzes on tailings dam of the different slope ratio, which under earthquake dynamic response characteristics and stability. The results show that, with the increase of the tailings dam slope than the maximum relative displacement becomes larger, the absolute acceleration amplification factor decreases. In the same slope ratio, the tailings dam displacement and maximum acceleration dam piled high with increased accumulation becomes larger. Sand soil absorption of seismic waves of high frequency, low frequency component.