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Embankment Dam Seepage and Slope Stability Analysis: The Case of Arjo-dedessa Dam, Ethiopia
Issue:
Volume 6, Issue 4, August 2021
Pages:
104-109
Received:
25 June 2021
Accepted:
10 July 2021
Published:
2 August 2021
Abstract: Dams have one of the greatest significant roles in operating water resources. Seepage and slope stability failures cause completely failure of embankment dams. Dam disasters not only hazard community safety, they also can cost our economy millions of dollars in compensations. The study area is found in Oromia regional state between East Wollega and Bunno Bedele Zone. The dam is located on Dedessa River, tributary of Blue Nile River. Analysis of seepage quantity was done by Darcy’s phreatic line, and SEEP/W software model for both homogeneous and zoned dam. The expected quantity of seepage estimated with the SEEP/W software model analysis that includes foundation seepage is 6.6*10-6m3/sec. Slope stability study is to contribute to the safe and economic design of upstream and downstream slope of the dam. The factory of safety obtained by Morgenstern-Price method for end construction is (FOS=1.99), for steady state (FOS=2.03) and rapid drawdown (FOS=2.91). However, at the design document shell material hadn’t been designed properly. Finally the paper concluded that the likely corrective measures for seepage controls are impermeable blanket, grouting, and the downstream slope miscarriage by eliminating the pathetic zone and seal with like graded quantifiable, regular repairs and shield the downstream slope with grasses.
Abstract: Dams have one of the greatest significant roles in operating water resources. Seepage and slope stability failures cause completely failure of embankment dams. Dam disasters not only hazard community safety, they also can cost our economy millions of dollars in compensations. The study area is found in Oromia regional state between East Wollega and...
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Assessment of the Semi-Adiabatic Temperature Rise of Mass Concrete Containing Bagasse Ash
Amanuel Bersisa,
Adil Zekaria
Issue:
Volume 6, Issue 4, August 2021
Pages:
110-119
Received:
16 July 2021
Accepted:
4 August 2021
Published:
27 August 2021
Abstract: Previous studies show that pozzolan materials are a wise choice for retarding significant heat in mass concrete placements. This research aims at studying the early age thermal property of concrete containing bagasse ash under different ambient temperatures. Moreover, the compressive strength of concrete specimens with varying ratios of the mix is assessed. Semi-adiabatic temperature rise data of four different concrete mixtures (containing pure Portland cement, 6.5%, 13%, and 20% dosage of bagasse ash by volume) are determined. Concrete specimens of size 30cm*30cm*40cm were cast and insulated using Styrofoam. The temperature measurement is taken at three different locations for every 30 minutes of interval. The influence of ambient temperature on specimens' early age thermal response is studied using a temperature chamber capable of simulating 25.15°C, 35.54°C, and 43.77°C average ambient temperatures. The results indicated that bagasse ash could replace the cement up to an optimum replacement level of 10 percent even if an early age strength drop is observed. The experiment revealed that the bagasse ash in the concrete mixture shift the temperature rise-time profile, reduces the total heat of hydration, and decreases the thermal gradient in the specimens. The peak temperature gauge of all mixes elevated as the ambient temperature increased, but mixtures containing bagasse ash show a slower heat liberation rate relative to the control group. The study proves pozzolan reaction is slow, releasing heat over a long period and not taking place early. It has merit in a massive concrete placement where cooling can lead to cracking following a significant temperature rise.
Abstract: Previous studies show that pozzolan materials are a wise choice for retarding significant heat in mass concrete placements. This research aims at studying the early age thermal property of concrete containing bagasse ash under different ambient temperatures. Moreover, the compressive strength of concrete specimens with varying ratios of the mix is ...
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Study of Eccentric and Buckling-Restrained Bracing Systems Used in Frames
Issue:
Volume 6, Issue 4, August 2021
Pages:
120-125
Received:
16 May 2021
Accepted:
15 August 2021
Published:
31 August 2021
Abstract: The present paper studies eccentric braces (EBs) and buckling-restrained braces (BRBs) used in steel frames. The eccentrically braced frames (EBFs) and buckling-restrained braced frames (BRBFs) that have respectively employed the EBs and BRBs are considered with different types of links as shear, moment-shear and moment links depending on their link length which is an important factor in the design of the EBFs and BRBFs. The BRB consists of a steel core and its surrounding steel tube filled with concrete. The concrete confinement prevents buckling of the steel core. The analysed EBFs and BRBFs by the finite element software ABAQUS under earthquake records are taken into account. Effects of the links of the EBFs and BRBFs on the performance of the frames are discussed. The results uncover that most of the lateral displacements of the EBFs and BRBFs having the shear link are smaller than their counterparts having the moment-shear and moment links, whilst, all the base shear capacities of the former are the greatest. However, majority of the EBFs and BRBFs with the moment link dissipate less energy than their counterparts with the shear and moment-shear links, whereas, most of the link rotations of the former are smaller than the latter. In addition, the BRBFs generally demonstrate better performance than their EBF counterparts.
Abstract: The present paper studies eccentric braces (EBs) and buckling-restrained braces (BRBs) used in steel frames. The eccentrically braced frames (EBFs) and buckling-restrained braced frames (BRBFs) that have respectively employed the EBs and BRBs are considered with different types of links as shear, moment-shear and moment links depending on their lin...
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