Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone

Simeon Stevenson Turay; Osman Koroma; Abdul Ahmed Koroma

doi:doi:10.11648/j.ijmsa.20200906.11

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Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone

Simeon Stevenson Turay, Osman Koroma, Abdul Ahmed Koroma

Published in International Journal of Materials Science and Applications (Volume 9, Issue 6)

Received: 21 June 2020 Accepted: 10 July 2020 Published: 16 December 2020

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Abstract

Earth slopes stability analysis is important in the design and construction of earth dams under different loading conditions. Several factors such as difference in water level or rapid drawdown in the reservoir, right after construction, and steady - state seepage may result in instability of Earth Dams for all possible combinations. In this study, three scenarios were evaluated for the Gbeni Earth Dam (GB3) at Sierra Rutile Mining Company in Sierra Leone. It is a zoned earth-filled embankment dam with respective upstream and downstream slopes of 1:3 and 1:2, having a horizontal sand blanket downstream. The upstream slope was subjected to both rapid drawdown in the reservoir of the earth dam and end of construction condition when there is no water present in the reservoir, whilst the downstream slope was assessed for steady seepage and end of construction conditions. The shape of the critical slip surface of both slopes was evaluated using a circular failure surface. The objective of this study was to assess the stability of these slopes under the above conditions using traditional analysis according to the theory of limit states and safety factor in GEO 5 software and its subprograms. The level of water on the upstream and downstream banks, the geotechnical properties of soil materials and boundary conditions of the dam were used as contribution variables and safety factors as the desired output. The study found out that the factor of safety against sliding of the upstream slope marginally drops within the short period after the start of rapid drawdown of water in the reservoir of the dam. Also, the downstream slope was found to be more stable under steady seepage. This accounts for the uncertainties involved in the strength of material, pore pressures in impervious clay core material, and long-term loading condition.

Published in	International Journal of Materials Science and Applications (Volume 9, Issue 6)
DOI	10.11648/j.ijmsa.20200906.11
Page(s)	66-70
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2020. Published by Science Publishing Group

Keywords

Rapid Drawdown, Steady – State Seepage, Limit States Equilibrium, Safety Factor, GEO 5 Software

References

[1]	Bishop, A. W., & Bjerrum, L. (1960). The relevance of the triaxial test to the solution of stability problems. Proc. Research Conference Shear Strength of Cohesive Soils, (pp. 437-501).
[2]	Coduto, D. P. (1999). Geotechnical Engineering Principles and Practices. New Jersey: Alan Apt.
[3]	Craig, R. F. (2004). Craig’s Soil Mechanics (7th ed.). Spon Press.
[4]	Das, B. M. (2007). Advanced Soil Mechanics (Third ed.). Taylor & Francis.
[5]	Duncan, J. M. (1996). State of the Art: Limit equilibrium and finite element analysis of slopes. J. Geotech. Eng, ASCE, 122, 577-596.
[6]	Fattah, M. Y., Omran, H. A., & Hassan, M. A. (2015). Behavior of an Earth Dam during Rapid Drawdown of Water in Reservoir – Case Study. International Journal of Advanced Research, 110-122.
[7]	Fellenius, W. (1936). Calculation of the Stability of Earth Dams. Transactions, 2nd International Congress on Large Darns (pp. 445-459). Washington, DC: International Commission on Large Dams.
[8]	Khanna, R., Datta, M., & Ramana, G. V. (2014). End-of-construction stability of earth and rockfill dams. Proceedings of Indian Geotechnical Conference IGC-2014. Kakinada, India.
[9]	Paton, J., & Semple, N. G. (1961). Investigation of the stability of an earth dam subjected to rapid drawdown including details of pore pressure recorded during a controlled drawdown test. Pore pressure and suction in soils. 85-90.
[10]	Sherard, J. L., Woodward, R. J., Gizienski, S. F., & Clevenger, W. A. (1963). Earth and earth-rock dams. New York: John Wiley and Sons.
[11]	Stark, T. D., & Jafari, N. H. (2017). Rapid Drawdown Stability Analysis of San Luis Dam. 3rd North American Symposium on Landslides. Roanoke, Virginia, USA.
[12]	Terzaghi, K., & Peck, R. B. (1948). Soil Mechanics in engineering practice. New York: Wiley.

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APA Style

Simeon Stevenson Turay, Osman Koroma, Abdul Ahmed Koroma. (2020). Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone. International Journal of Materials Science and Applications, 9(6), 66-70. https://doi.org/10.11648/j.ijmsa.20200906.11

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ACS Style

Simeon Stevenson Turay; Osman Koroma; Abdul Ahmed Koroma. Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone. Int. J. Mater. Sci. Appl. 2020, 9(6), 66-70. doi: 10.11648/j.ijmsa.20200906.11

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AMA Style

Simeon Stevenson Turay, Osman Koroma, Abdul Ahmed Koroma. Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone. Int J Mater Sci Appl. 2020;9(6):66-70. doi: 10.11648/j.ijmsa.20200906.11

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@article{10.11648/j.ijmsa.20200906.11,
  author = {Simeon Stevenson Turay and Osman Koroma and Abdul Ahmed Koroma},
  title = {Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone},
  journal = {International Journal of Materials Science and Applications},
  volume = {9},
  number = {6},
  pages = {66-70},
  doi = {10.11648/j.ijmsa.20200906.11},
  url = {https://doi.org/10.11648/j.ijmsa.20200906.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijmsa.20200906.11},
  abstract = {Earth slopes stability analysis is important in the design and construction of earth dams under different loading conditions. Several factors such as difference in water level or rapid drawdown in the reservoir, right after construction, and steady - state seepage may result in instability of Earth Dams for all possible combinations. In this study, three scenarios were evaluated for the Gbeni Earth Dam (GB3) at Sierra Rutile Mining Company in Sierra Leone. It is a zoned earth-filled embankment dam with respective upstream and downstream slopes of 1:3 and 1:2, having a horizontal sand blanket downstream. The upstream slope was subjected to both rapid drawdown in the reservoir of the earth dam and end of construction condition when there is no water present in the reservoir, whilst the downstream slope was assessed for steady seepage and end of construction conditions. The shape of the critical slip surface of both slopes was evaluated using a circular failure surface. The objective of this study was to assess the stability of these slopes under the above conditions using traditional analysis according to the theory of limit states and safety factor in GEO 5 software and its subprograms. The level of water on the upstream and downstream banks, the geotechnical properties of soil materials and boundary conditions of the dam were used as contribution variables and safety factors as the desired output. The study found out that the factor of safety against sliding of the upstream slope marginally drops within the short period after the start of rapid drawdown of water in the reservoir of the dam. Also, the downstream slope was found to be more stable under steady seepage. This accounts for the uncertainties involved in the strength of material, pore pressures in impervious clay core material, and long-term loading condition.},
 year = {2020}
}

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TY  - JOUR
T1  - Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone
AU  - Simeon Stevenson Turay
AU  - Osman Koroma
AU  - Abdul Ahmed Koroma
Y1  - 2020/12/16
PY  - 2020
N1  - https://doi.org/10.11648/j.ijmsa.20200906.11
DO  - 10.11648/j.ijmsa.20200906.11
T2  - International Journal of Materials Science and Applications
JF  - International Journal of Materials Science and Applications
JO  - International Journal of Materials Science and Applications
SP  - 66
EP  - 70
PB  - Science Publishing Group
SN  - 2327-2643
UR  - https://doi.org/10.11648/j.ijmsa.20200906.11
AB  - Earth slopes stability analysis is important in the design and construction of earth dams under different loading conditions. Several factors such as difference in water level or rapid drawdown in the reservoir, right after construction, and steady - state seepage may result in instability of Earth Dams for all possible combinations. In this study, three scenarios were evaluated for the Gbeni Earth Dam (GB3) at Sierra Rutile Mining Company in Sierra Leone. It is a zoned earth-filled embankment dam with respective upstream and downstream slopes of 1:3 and 1:2, having a horizontal sand blanket downstream. The upstream slope was subjected to both rapid drawdown in the reservoir of the earth dam and end of construction condition when there is no water present in the reservoir, whilst the downstream slope was assessed for steady seepage and end of construction conditions. The shape of the critical slip surface of both slopes was evaluated using a circular failure surface. The objective of this study was to assess the stability of these slopes under the above conditions using traditional analysis according to the theory of limit states and safety factor in GEO 5 software and its subprograms. The level of water on the upstream and downstream banks, the geotechnical properties of soil materials and boundary conditions of the dam were used as contribution variables and safety factors as the desired output. The study found out that the factor of safety against sliding of the upstream slope marginally drops within the short period after the start of rapid drawdown of water in the reservoir of the dam. Also, the downstream slope was found to be more stable under steady seepage. This accounts for the uncertainties involved in the strength of material, pore pressures in impervious clay core material, and long-term loading condition.
VL  - 9
IS  - 6
ER  -

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Author Information

Simeon Stevenson Turay

Department of Civil Engineering, University of Sierra Leone, Freetown, Sierra Leone
Osman Koroma

Department of Civil Engineering, University of Sierra Leone, Freetown, Sierra Leone
Abdul Ahmed Koroma

Department of Civil Engineering, University of Sierra Leone, Freetown, Sierra Leone

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APA Style

Simeon Stevenson Turay, Osman Koroma, Abdul Ahmed Koroma. (2020). Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone. International Journal of Materials Science and Applications, 9(6), 66-70. https://doi.org/10.11648/j.ijmsa.20200906.11

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ACS Style

Simeon Stevenson Turay; Osman Koroma; Abdul Ahmed Koroma. Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone. Int. J. Mater. Sci. Appl. 2020, 9(6), 66-70. doi: 10.11648/j.ijmsa.20200906.11

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AMA Style

Simeon Stevenson Turay, Osman Koroma, Abdul Ahmed Koroma. Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone. Int J Mater Sci Appl. 2020;9(6):66-70. doi: 10.11648/j.ijmsa.20200906.11

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@article{10.11648/j.ijmsa.20200906.11,
  author = {Simeon Stevenson Turay and Osman Koroma and Abdul Ahmed Koroma},
  title = {Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone},
  journal = {International Journal of Materials Science and Applications},
  volume = {9},
  number = {6},
  pages = {66-70},
  doi = {10.11648/j.ijmsa.20200906.11},
  url = {https://doi.org/10.11648/j.ijmsa.20200906.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijmsa.20200906.11},
  abstract = {Earth slopes stability analysis is important in the design and construction of earth dams under different loading conditions. Several factors such as difference in water level or rapid drawdown in the reservoir, right after construction, and steady - state seepage may result in instability of Earth Dams for all possible combinations. In this study, three scenarios were evaluated for the Gbeni Earth Dam (GB3) at Sierra Rutile Mining Company in Sierra Leone. It is a zoned earth-filled embankment dam with respective upstream and downstream slopes of 1:3 and 1:2, having a horizontal sand blanket downstream. The upstream slope was subjected to both rapid drawdown in the reservoir of the earth dam and end of construction condition when there is no water present in the reservoir, whilst the downstream slope was assessed for steady seepage and end of construction conditions. The shape of the critical slip surface of both slopes was evaluated using a circular failure surface. The objective of this study was to assess the stability of these slopes under the above conditions using traditional analysis according to the theory of limit states and safety factor in GEO 5 software and its subprograms. The level of water on the upstream and downstream banks, the geotechnical properties of soil materials and boundary conditions of the dam were used as contribution variables and safety factors as the desired output. The study found out that the factor of safety against sliding of the upstream slope marginally drops within the short period after the start of rapid drawdown of water in the reservoir of the dam. Also, the downstream slope was found to be more stable under steady seepage. This accounts for the uncertainties involved in the strength of material, pore pressures in impervious clay core material, and long-term loading condition.},
 year = {2020}
}

Copy | Download

TY  - JOUR
T1  - Slope Stability Analysis of the Gbeni Earth Dam (GB3) in Rutile - Sierra Leone
AU  - Simeon Stevenson Turay
AU  - Osman Koroma
AU  - Abdul Ahmed Koroma
Y1  - 2020/12/16
PY  - 2020
N1  - https://doi.org/10.11648/j.ijmsa.20200906.11
DO  - 10.11648/j.ijmsa.20200906.11
T2  - International Journal of Materials Science and Applications
JF  - International Journal of Materials Science and Applications
JO  - International Journal of Materials Science and Applications
SP  - 66
EP  - 70
PB  - Science Publishing Group
SN  - 2327-2643
UR  - https://doi.org/10.11648/j.ijmsa.20200906.11
AB  - Earth slopes stability analysis is important in the design and construction of earth dams under different loading conditions. Several factors such as difference in water level or rapid drawdown in the reservoir, right after construction, and steady - state seepage may result in instability of Earth Dams for all possible combinations. In this study, three scenarios were evaluated for the Gbeni Earth Dam (GB3) at Sierra Rutile Mining Company in Sierra Leone. It is a zoned earth-filled embankment dam with respective upstream and downstream slopes of 1:3 and 1:2, having a horizontal sand blanket downstream. The upstream slope was subjected to both rapid drawdown in the reservoir of the earth dam and end of construction condition when there is no water present in the reservoir, whilst the downstream slope was assessed for steady seepage and end of construction conditions. The shape of the critical slip surface of both slopes was evaluated using a circular failure surface. The objective of this study was to assess the stability of these slopes under the above conditions using traditional analysis according to the theory of limit states and safety factor in GEO 5 software and its subprograms. The level of water on the upstream and downstream banks, the geotechnical properties of soil materials and boundary conditions of the dam were used as contribution variables and safety factors as the desired output. The study found out that the factor of safety against sliding of the upstream slope marginally drops within the short period after the start of rapid drawdown of water in the reservoir of the dam. Also, the downstream slope was found to be more stable under steady seepage. This accounts for the uncertainties involved in the strength of material, pore pressures in impervious clay core material, and long-term loading condition.
VL  - 9
IS  - 6
ER  -

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