Dam Slope Stability Research Articles

Seismic reliability assessment of earth-rockfill dam slopes considering strain-softening of rockfill based on generalized probability density evolution method

This paper investigates the seismic reliability of earth-rockfill dam slopes under stochastic earthquake excitation considering strain-softening behaviour of rockfill materials. A new and efficient methodology that couples a recently developed generalized probability density evolution method (GPDEM) with a spectral representation-random function method is presented to assess the seismic reliability. To solve the GPDEM equation, the stochastic seismic responses analysis of a 242-m concrete face rockfill dam (CFRD) is translated into a series of deterministic dynamic calculations. The probability information and seismic reliability of the safety factor demonstrate that the results between the simulations considering unsoftening and softening behaviour of the rockfill materials become increasingly different as the earthquake intensifies, and strain-softening behaviour gradually appear under seismic excitation. Thus, considering the softening characteristic of rockfill materials, is of great significance to analyze the seismic safety of high earth rockfill dams. The traditional index for evaluating dam slope stability with safety factor is compared with a new index the cumulative time of the safety factor less than 1.0 (Fs < 1.0), suggesting that the new index is more reasonable to assess the seismic reliability of dam slopes. The results indicate that the GPDEM is an effective approach to seismic reliability assessment from the stochastic viewpoint and can directly reflect the failure probability.

Grouting design for slope stability of kedung uling earthfill dam

Kedung Uling earthfill dam locates at Wonogiri Regency, Central Java, Indonesia. The dam encountered sliding and settlement at the embankment wall. To minimize sliding and settlement and to optimize the dam, both field investigation and laboratory tests have been proceeded for slope stability analysis and remedial embankment wall. Soil and rock investigation around the dam, which is followed by 10 core drillings, have been conducted. Laboratory tests such as direct shear and index properties have also been carried on. The results were further used for dam slope stability model using slide 6.0 and were used to analyzed factor of safety (FS) of Kedunguling dam. 10 conditions of dam were simulated and strengthening body of dam with grouting was designed. The results showed two conditions, which are condition of maximum water level with and without earthquake at downstream, were unsatisfy Indonesia National Standard (SNI) for building and infrastructure. These conditions can be managed by using grouting for increasing stabilization of embankment wall. By setting up grouting, factor of safety increases and meet the SNI standard requirement.

Slope Stability Evaluation of Reinforcement Effect for Fengchan Earth Dam

Based on the typical section of the dam and geological survey data, the model for analyzing the stability of the typical section of the dam slope is established. In this paper, the calculation model is used to compute the stability of dam slope in the Fengchan reservoir before and after the reinforcement. The results show that the condition of dam slope stability is better. After the reinforcement, the seepage slope of each partition and seepage discharge decrease significantly and the stability safety factors of dam slope in various engineering conditions increase obviously, which can meet the requirements of specification.

Major Technologies for Safe Construction of High Earth-Rockfill Dams

Abstract The earth-rockfill dam is one of the primary dam types in the selection of high dams to be constructed in Western China, since it is characterized by favorable adaptability of the dam foundation; full utilization of local earth, rock, and building-excavated materials; low construction cost; and low cement consumption. Many major technical issues regarding earth-rockfill dams with a height of over 250 m were studied and solved successfully in the construction of the 261.5 m Nuozhadu earth core rockfill dam. This paper describes research achievements and basic conclusions; systematically summarizes the accumulated experiences from the construction of the Nuozhadu Dam and other high earth-rockfill dams; and discusses major technical issues, such as deformation control, seepage control, dam slope stability, safety and control of flood discharging, safety and quality control of dam construction, safety assessments, early warning, and other key technical difficulties. This study also provides a reference and technological support for the future construction of 300 m high earth-rockfill dams.

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.

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.

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.

Research on Safety Factor of Dam Slope of High Embankment Dam under Seismic Condition

With the constant development of construction technology of embankment dam, the constructed embankment dam becomes higher and higher, and the embankment dam with its height over 200m will always adopt the current design criteria of embankment dam only suitable for the construction of embankment dam low- er than 200m in height. So the design criteria of high embankment dam shall be improved. We shall calculate the stability and safety factors of dam slope of high embankment dam under different dam height, slope ratio and different seismic intensity based on ratio of safety margin, and clarify the change rules of stability and safety factors of dam slope of high embankment dam with its height over 200m. We calculate the ratio of safety margin of traditional and reliable method by taking the stable, allowable and reliability index 4.2 of dam slope of high embankment dam with its height over 200m as the standard value, and conduct linear regression for both. As a result, the conditions, where 1.3 is considered as the stability and safety factors of dam slope of high embank- ment dam with its height over 200m under seismic condition and 4.2 as the allowable and reliability index, are under the same risk control level.

Analysis of Unsteady Seepage Behavior of Rumei High Core Wall Rockfill Dam by FEM

The Rumei core wall rockfill dam hydropower station is in Lancang River in the Mangkang county of the Tibet autonomous region with maximum height of 315m and crest length of 666.2m. Due to the high core wall rockfill dam has been more than 300m high, water level sudden drawdown of the unsteady seepage condition shall be taken into consideration, according to the given water level drop speed (5m/d) calculate condition, analysis of the seepage field distribution of the different water level, free surface of different time, each material partition of the dam and foundation soil seepage gradient, etc are given. The results showed that the free surface of the upstream dam shell rockfill body dropping fast than the water level dropping speed of the reservoir. The seepage gradient of the upstream shell is very small, which will not cause adverse effect on the upstream dam slope stability. The free surface of the downstream dam shell rockfill body changes little, which will not cause adverse effect on the downstream of the dam slope stability. As the water level falls, the free surface of the core wall dropping speed is slow, far less than the water dropping speed of the reservoir. In the process of emptying reservoir, the free surface of the core wall remains in a high position, which should cause enough attention.

Analysis of dam slope stability by double safety factors and dynamic local strength reduction method

Strength reduction method has been widely used in dam slope stability analysis. However the traditional strength reduction method does not take into account the difference of decay rate of cohesion and internal friction angle in the dam slope failure process. Besides, this method discounts the strength parameters of all elements. This paper adopts different reduction factors for material strength parameters, such as slope cohesion and internal friction angle. Based on the yield approach index (YAI) criterion, this paper adjusts the reduction region gradually and puts forward the double safety factor and the dynamic local strength reduction method for the dam slope stability analysis. A case study with a typical example shows that this method can better reflect the decay rate difference of cohesion and internal friction angle in the dam slope failure, further it can provide better simulation for the slope failure processes. The safety factor of this method is generally less than that of traditional strength reduction and dynamic local strength reduction method. This new method can better overcome the two defects encountered in the traditional strength reduction methods.

Analysis about the Influence of Clay Core Wall Structure towards the Slope Stability of High Embankment Dam

As the main part of the anti-seepage system, core wall is a key point in the design of high em-bankment dam. The dam slope stability is a major factor for the type of core wall. But it is still unclear what effects the core wall structure might have on the slope stability. Based on practical projects of high embankment dam in Nuozhadu, Lianghekou and Shuangjiangkou, this paper analyzes safety factors and dangerous slip sur-faces of dam slopes of high embankment dams in both straight and slanting core wall structures and compares the influences of different core wall structures on the slope stability of high embankment dam through numerical calculations. The safety margin of the embankment dam of straight core wall is larger than that of slanting core wall in the operating condition of the reservoir water level’s drawdown. Compared with that of the straight core wall scheme, the position of the dangerous slip surface of the downstream dam slope is closer to the dam crest in the slanting core wall scheme.

Impact of Seismicity on Stability of Earthen Dam Slopes

The impact of seismicity on stability of earthen dam slopes is discussed in the article. The analysis of the slope stability of the Domaša Dam was carried out. Petterson, Bishop and Sarma methods were employed for the calculations while taking into account the seismic actions according to EN1998-1.

Methods for Analyzing the Stability of an Earthen Dam Slope

The slope stability of a water construction in four cross-profiles is analyzed in the article and the factors of safety reviewed. The GEO 5 software package for slope stability calculations is an essential component of work. The computer software was employed to simulate and calculate the stability in the particular profiles of the downstream and upstream slopes of the Domaša Dam. Bishop, Petterson and Sarma methods were applied to determine the critical factors of safety.

Research of Embankment Dam Structural Safety

A concrete embankment dam, for example, to run for the water control dam for many years conducted a vertical displacement, horizontal displacement data analysis and research; and the review of the dam slope stability, structural stability of the main dam crest review, analysis and research of the results,give the conclusion of the reasonable evaluation. Provide reference for the safety evaluation about the aging and dangerous water Construction.

Seismic Analysis of an Earth-Rock Dam on Thick Alluvial Deposit

The nonlinear dynamic FEM was applied to analyze the dynamic response of a core-wall earth-rock dam on thick loess alluvial deposit. The dynamic responses of acceleration, dynamic displacement, permanent deformation and the liquefaction state of the dam were obtained. Meanwhile, both dynamic FEM limit equilibrium method and pseudo-static method were used to access the seismic resistance of dam slope stability. The results show that dynamic responses of acceleration and dynamic displacement are reasonable. The permanent deformation is mainly concentrated in the core wall. The downstream dam slope has enough seismic resistance stability. However, there will be big dynamic pore-water pressure in the dam foundation and the loess alluvial deposit will be liquefied during the earthquake. Therefore the resistance method of liquefaction should be adopted for the foundation.

Safety Analysis of the Temporary Dam Body of Concrete Faced Rockfill Dam during Construction Period

Concrete faced Rockfill dam (CFRD) is a safe and economical dam type in hydraulic engineering. The temporary dam body for flood control during construction period is usually used for CFRD, so the safety of temporary dam body during construction period is very important. Based on numerical simulation of the seepage field of the temporary dam body of CFRD using nonlinear FEM (Finite Element Method) under the action of flood of the river during construction period, the stability of the dam slope is studied. The effectiveness and applicability of the method introduced is certified through computation in the study on the practical project. The paper provides an effective analysis method for the study on the stability of dam slope of the temporary dam body of CFRD for flood control during construction period.

Analysis of Earth-Rockfill Dam Slope Stability by Strength Reduction Method Based on Nonlinear Strength

In the design process of the earth-rock dam, the slope stability problem was always focused on. The shear strength of rockfill in the earth-rock dam had strong nonlinear characteristics. The characteristic directly affected the factor of safety (FOS) of stability of dam slope and the determination of the critical slip surface. The shear strength parameter of rockfill was related to the minimum principal stress σ3 closely. And the value of σ3 had close relationship with the deformation characteristics of filling material and the process of dam filling etc. Strength reduction method has been widely used in solving the FOS of slope stability, and this method has the advantage on the searching of the critical slip surface. Combining the deformation and stress analysis of earth-rockfill dam filling process and the strength reduction method, this paper proposes a comprehensive method of dam slope stability analysis.