Uplift pressure and hydraulic gradient in Sabalan Dam (original) (raw)
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Effects of Upstream Slope of Clay Core and Height of the Rock Fill Dams Against Hydraulic Fracturing
Jurnal Teknologi, 2016
Hydraulic fracturing in rock fill dams may occur in case where the upstream face of the clay core experiencing tension cracks due to the arching effects and water pressure from the reservoir. One of the causes of arching effects was the steep slope of the upstream clay core. A statistical research on the dam experiencing with hydraulic fracturing indicated that rock fill dams with un-compacted rock fill embankment zone with narrow and steep slope of core, where the ratio between height against base width of core > 2 were considered much more likely for hydraulic fracturing to occur, while if the ratio was between 1 to 2 were considered likely to occur. This paper investigates the height limitation of the rock fill dams on the ratio of the height against the base width of core of 2.00 and 2.50, which represent the conditions of more likely and much more likely hydraulic fracturing to occur. The clay cores were obtained from five (5) major dams in Indonesia; Batubulan, Batutegi, Pe...
Effect of Inclined Clay Core on Embankment Dam Seepage and Stability Through LEM and FEM
Geotechnical and Geological Engineering, 2020
Water seepage affects dam stability and loss of water from reservoirs. Consequently, seepage is an important problem in the design, implementation, and operation of embankment dams. One type of embankment dam is a non-homogeneous (zoned) dam with a clay core. Water passes through the core of the dam and loses much of its energy due to friction. Zoned embankment dams can be designed and implemented with inclined or vertical cores. In this study, the performance of inclined and vertical cores are compared using numerical models to simulate the seepage and hydraulic gradients. Also, the Limit of Equilibrium Method is used to calculate slope stability. The permeability ratio of the dam shell to the clay core is a variable. The result of this study shows that seepage with a vertical core is less than that with an inclined core. Meanwhile, the factor of safety for upstream slope failure is higher (about 55.5%) for the embankment with an inclined core compared to the vertical core case. Also, comparisons were made using different methods to calculate the stability of the slope. The Bishop's method showed the highest safety factor and the Fellenius' method predicts the lowest safety factor.
Effect of Width, Length and Position of Cutoff Wall on the Seepage Characteristics of Earth Dam
2019
Seepage is one of the main causes of failure of earthen dam. To encounter the seepage through the foundation of dam, construction of cut off wall is a frequently used and a conventional technique. In this study, several numbers of numerical analysis are performed against different widths and lengths of the cut off wall for different positions along the cross section of the dam to find out the appropriate one. All these analyses are performed for a homogeneous dam with foundation soil being clay and silty clay. Numerical analyses are conducted by SEEP/W (a sub program of geo studio). The numerical results depict that the best possible position of the cut off wall is at the downstream toe of the dam. This is because, in this position, most number of flow lines gets encountered by cutoff wall. It is also observed that the effect of the width of cutoff wall on the total head and pore water pressure (PWP) is negligible but it affects the velocity of seepage and total discharge. On the ot...
Engineering and Technology Journal
In this study, the rate of seepage flow through the dam was investigated using both experimental and numerical modeling techniques. Two different types of soil samples were collected at a depth of 1m from the Auchi site in Edo State, Nigeria. The soil samples were subjected to preliminary tests such as the sieve analysis, the limit state (liquid limit, plastic limit and plasticity index), and the specific gravity test. Notable differences in the Geotechnical properties of two samples of soils were observed. The sieve analysis indicated that the particles passing through a 200-sieve number of size 0.075mm were 14.32% and 13.48% respectively. The liquid limit of sample 1 and sample 2 was determined to be 35% and 30%, the plastic limit 20.5% and 24.3%, the plasticity index 14.5% and 5.7% and the specific gravity of the two samples 2.63 and 2.65 respectively. Shear test was conducted to obtain the bearing capacity of soil using Terzaghi principle thereafter, the finite element analysis ...
Evaluation of the Impact of Having of Expansive Clay Core on the Stability of an Earth Dam
Geotechnical Engineering Journal of the SEAGS&AGSSEA, 2024
The study focuses on the changes in seepage and stability of the dam with a clay core constructed with expansive soils. Heave potential of the expansive clay core was also evaluated in the study. Laboratory testing was conducted to evaluate the swelling potential and hydraulic properties for the compacted expansive soils under various dry unit weights and initial water contents. Numerical modeling was conducted to evaluate the changes in seepage flow and slope stability due to the heaving of the expansive clay core for the dam. The findings suggest that to reduce seepage flow, the swelling soil should be compacted to a lower degree of compaction at a moisture content exceeding the optimum moisture content (OMC), which effectively reduces soil swelling and consequently minimizes seepage. Conversely, if stability is the primary concern, the swelling soil should be compacted to a relatively higher degree of compaction at a moisture content lower than the OMC, providing enhanced strength to the dam. In conclusion, the study demonstrates that for expansive soil used in dam cores, the same traditional compaction conditions utilized for seepage and stability in normal clayey soil can be applied. However, it is crucial to consider the specific characteristics of the swelling soil during the compaction process. By implementing suitable compaction techniques based on the desired outcome, seepage control, and dam stability can be effectively managed when utilizing swelling soil in dam construction. The findings offer valuable insights to engineers and practitioners involved in dam design and construction, aiding in informed decision-making and optimal compaction practices when incorporating swelling soils in dam cores.
Analysis and Design of a Deep Subsurface Dam
ijens.org
A 3-D finite element (FE) numerical model was used to analyze structurally a proposed subsurface concrete dam to serve as a strategic water supply storage for the Holy city of Makkah, S audi Arabia. The work was done mainly to show the behavior of the subsurface dam under the subjecting loads. The plastic concrete was chosen for the construction of the cutoff wall required for the reservoir. Three-dimensional finite element analyses were made for three thicknesses of the cutoff walls: 0.6 to 0.8 m, 0.8 to 1.0 m and 1.0 to 1.2 m for the alluvium depths of 30, 50 and 70 m, respectively. The change in soil rigidity with depth was taken into account. The vertical and horizontal boundary conditions were designed to simulate the proper behavior of the structure It was found that increasing the thickness of the wall improves the distribution of the mobilized passive pressure opposite to the water pressure acting on the upstream face of the cutoff wall, while, the vertical and horizontal stresses developed in the wall due to the applied loads increased. In addition, stresses in the wall increase incrementally with the increase of wall height. The maximum horizontal and vertical stresses developed in proportion to the 1/6 bottom height of the wall. In the lower part of the wall, the mix with rich cement content must be used. It is recommended also to use vertical reinforcement imbedded by the anchorage length in the lock of the wall inside the bedrock and extended 1/20 the wall height. Results showed that the two vertical boundaries in the FE mesh must be placed at minimum distance equaling twice the height of the alluvium deposits from the centerline of the cutoff wall.. Index Termsubsurface dam analysis, cutoff wall analysis, underground dam analysis, structural analysis of dams. I.
Effects of material properties on behavior of embankment dam clay cores in narrow valleys
Scientia Iranica, 2015
In this study, stress-strain analyses of embankment dams with clay core in narrow valleys are evaluated by means of numerical modeling, considering the longitudinal section along an embankment dam centerline. Emphasis is placed on effects of cross valley differential settlements, and the end of construction core load-settlement behavior, particularly in vicinity of abutments. The effects of core material type (mixed clayey sand material versus pure clay), on stress-strain behavior are examined. As a case study the Masjed Soleyman clay core is analyzed considering different types of materials, and a range of core material deformation properties. A 70% reduction in depth of tensile zones near the core- abutment interface was achieved by inclusion of contact clay material at the core bottom. Comparison of analysis results and instrumentation data suggested a good agreement between results.
Analysis and Design of Earth and Rockfill Dams
2016
Hydropower or water power is a reliable, environment friendly and affordable source of electricity generation. The increased development and expansion of population in India’s north eastern region, has created a definite need of hydropower for electricity generation. To meet the current as well as future demands, the available hydropower needs can be harnessed by building dams for storage and management of water for hydropower, and also addition of additional storage at existing dams for the same. As such, this paper concentrates on a case from a proposed dam of a hydro-electric project in the North East region, which has been taken up for analysis and design. The concerned dam is to be built as an earth dam. The dam section has been assumed as per the required criteria and analyzed using GEOSTUDIO software. Analysis is done for the static case. Seepage analysis and stability investigation are very important issues that should be considered for design. Hence, seepage analysis is con...
Effect of Variation in Vertical Core Thickness on Stability Analysis of Earth and Rockfill Dams
Construction of earth and rockfill dams allows the use of available soil of different gradations in appropriate zones of dam cross section. Moreover the flexibility of the materials provides excellent seismic stability to the structure. Thus it requires evaluating the stability analysis of zoned dam with different materials and hydraulic properties of the construction materials. The stability of the dams depends on its geometry, materials properties and the forces to which it is subjected. These forces include the effects of water in the form of pore water pressure and seepage forces. This paper presents stability analysis carried out on 185 m high earth and rockfill dam with upstream slope of 1V:2.50H and downstream slope of 1V:1.80H. Thickness of the vertical core was varied from 1V:0.25H to 1V:2.65H and its effect on slope stability was analyzed under three critical conditions i.e. during and end of construction, steady state seepage and rapid draw down for both upstream and downstream slope of dam in static condition by Limit Equilibrium Method using SLIDE 5.0 software. It was observed from the analysis that by varying the thickness of vertical core of earth and rockfill dam, thinner core up to 1V:1.30H gives more stability and further increase in thickness of core tends to sharp decline in factor of safety both for upstream and downstream slope under different critical conditions.
Numerical Analysis of Seepage in Earth-Fill Dams
Civil Engineering Journal, 2020
In an earth-fill dam, the effect of seepage has been studied by applying a finite element method using the SEEP2D program. This is in order to determine the quantity of seepage through the dam. The total head measurements, core permeability, and anisotropy ratio (kx/ky) (Case study: Khassa Chai Dam, Iraq) are taken as the main parameters. The effect of the different water heads of the reservoir were tested on the seepage. The results showed that any increase in the water heads caused an increase in seepage quantity. Also, it was found that the seepage rate decreases by about 8.7%, 13.2%, and 15.3% at levels of water 454, 471, and 485 m.a.s.l, respectively by changing the core permeability from 10-6 m/s to 10-7 m/s. It has been concluded that the clay core plays a significant role in decreasing the seepage quantity and existing gradient. The results of testing the effect of anisotropy ratio on seepage showed that an increase in (kx/ky) ratio leads to an increase in seepage quantity. ...