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Unsaturated Volcanic Tephra and Its Effect for Soil Movement in El Salvador

Published: 2 April 2013
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Abstract

In El Salvador during the rainy season or when major earthquakes affect the area, processes like mass move-ments, liquefaction, erosion and floods affect the territory leaving environmental, social and economic damages. The vol-canic tephras called "Tierra Blanca Joven" (TBJ) which is a product of the last plinian eruption of the Ilopango Caldera are the more problematic region in the Metropolitan Area of San Salvador. In El Salvador during the summer and rainy season the groundwater level remains low in most of the areas, this means that the soils in the country are unsaturated and there are capillary forces that act on the soil structure making that an “apparent cohesion” (suction) improve the strength of the soil; this circumstance makes that the slopes are almost vertical and temporally stable, but will collapse when wetted or during seismic events. To that problematic is possible to add that the majority of the water pipelines are in bad condition and when they fail is possible to expect the collapse of entire streets or houses. Wetting of the soil is likely to occur following construction development, because evaporation is reduced by covering the ground surface with a structure. For unsaturated soils the use of two independent stress variables: net stress and suction are needed. Suction values of TBJ “G” unit of the proximal facie were obtained using pressure plate, tensiometer and filter paper to obtain a Soil-Water Retention Curve (SWRC); the use of this curve into finite elements software can help to obtain the shear strength and permeability properties. For monitoring, the use of Quickdraw tensiometers (suction) and TMS3 (soil moisture content) is proposed, because it could be a way to build a field methodology for early warning system for the slopes for urban planning and risk assessment.

Published in Earth Sciences (Volume 2, Issue 2)
DOI 10.11648/j.earth.20130202.15
Page(s) 58-65
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), 2013. Published by Science Publishing Group

Keywords

Tierra Blanca Joven, Erosion, Mass Movement, Unsaturated, Suction, Tensiometer, Soil Moisture Sensor

References
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[5] R. Rolo, J.J. Bomer, B.F. Houghton, J. W. Vallance, P . Berdousis, C. Mavrommati and W. Murphy, "Geologic and engineering characterization of Tierra Blanca pyroclastic ash deposits", Geological Society of America, Special Paper 375, pp. 55-67, 2004.
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[10] D.G. Fredlund and H. Rahardjo, Soil mechanics for unsatu-rated soils, 1993, Wiley-Intescience Publications, p. 517.
[11] S. Houston, W. Houston, C. Zapata and C. Lawrence, "Geo-technical engineering practice for collapsible soils" in Un-saturated soil concepts and their application in geotechnical practice, Toll D, Eds. Kluwer Academic Publishers, 2001, pp. 333-355.
[12] C. A. Alvarado, "Modelo conceptual y vulnerabilidad intrínseca del acuífero Quezaltepeque-Nejapa", Universidad de El Salvador, p. 54, 2007.
[13] S. Houston and W. Houston, "Collapsible soil enginnering", in Unsaturated soil engineering practice, Houston S, Fredlund D, Eds. ASCE, New York, 1997, pp. 199-232.
[14] C. Ng, and B. Menzies, Advanced unsaturated soil mechanic and engineering. Taylor and Francis, 2007, p. 687.
[15] W. Savage, R. Baum, "Instability of steep slopes" in De-bris-flow hazards and related phenomena, M. Jakob and O. Hungr, Eds. Praxis Publishing, 2005, pp.53-79.
[16] D. G. Fredlund, H .Rahardjo and M.D. Fredlund, Unsaturated soil mechanics in engineering practice. John Wiley & Sons, 2012, p. 926.
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[18] W. S. Sillers, D.G. Fredlund and N. Zakerzadeh , "Mathe-matical attributes of some soil-water characteristic curve models " in Unsaturated soil concepts and their application in geotechnical practice, Toll D, Eds. Kluwer Academic Pub-lishers, 2001, pp. 243-283.
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[23] D.G. Fredlund, "An introduction to unsaturated soil mechanics" in Unsaturated soil engineering practice, Houston S, Fredlund D, Eds. ASCE, New York, 1997, pp. 1-37.
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[25] K. Bicalho, A. Correia, S. Ferreira, J-M. Fleureau and F. Marinho, "Filter paper method of soil suction measurement", Proceedings of XIII Panamerican Conference on Soil Me-chanics and Geotechnical Engineering, v. 1. p. 1-6., July 2007.
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Cite This Article
  • APA Style

    José Alexander Chávez Hernández, José Alexander Chávez Hernández, Jiři Šebesta, Lubomir Kopecky, Reynaldo López Landaverde, et al. (2013). Unsaturated Volcanic Tephra and Its Effect for Soil Movement in El Salvador. Earth Sciences, 2(2), 58-65. https://doi.org/10.11648/j.earth.20130202.15

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    ACS Style

    José Alexander Chávez Hernández; José Alexander Chávez Hernández; Jiři Šebesta; Lubomir Kopecky; Reynaldo López Landaverde, et al. Unsaturated Volcanic Tephra and Its Effect for Soil Movement in El Salvador. Earth Sci. 2013, 2(2), 58-65. doi: 10.11648/j.earth.20130202.15

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    AMA Style

    José Alexander Chávez Hernández, José Alexander Chávez Hernández, Jiři Šebesta, Lubomir Kopecky, Reynaldo López Landaverde, et al. Unsaturated Volcanic Tephra and Its Effect for Soil Movement in El Salvador. Earth Sci. 2013;2(2):58-65. doi: 10.11648/j.earth.20130202.15

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  • @article{10.11648/j.earth.20130202.15,
      author = {José Alexander Chávez Hernández and José Alexander Chávez Hernández and Jiři Šebesta and Lubomir Kopecky and Reynaldo López Landaverde and José Landaverde},
      title = {Unsaturated Volcanic Tephra and Its Effect for Soil Movement in El Salvador},
      journal = {Earth Sciences},
      volume = {2},
      number = {2},
      pages = {58-65},
      doi = {10.11648/j.earth.20130202.15},
      url = {https://doi.org/10.11648/j.earth.20130202.15},
      eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.earth.20130202.15},
      abstract = {In El Salvador during the rainy season or when major earthquakes affect the area, processes like mass move-ments, liquefaction, erosion and floods affect the territory leaving environmental, social and economic damages. The vol-canic tephras called "Tierra Blanca Joven" (TBJ) which is a product of the last plinian eruption of the Ilopango Caldera are the more problematic region in the Metropolitan Area of San Salvador. In El Salvador during the summer and rainy season the groundwater level remains low in most of the areas, this means that the soils in the country are unsaturated and there are capillary forces that act on the soil structure making that an “apparent cohesion” (suction) improve the strength of the soil; this circumstance makes that the slopes are almost vertical and temporally stable, but will collapse when wetted or during seismic events. To that problematic is possible to add that the majority of the water pipelines are in bad condition and when they fail is possible to expect the collapse of entire streets or houses. Wetting of the soil is likely to occur following construction development, because evaporation is reduced by covering the ground surface with a structure. For unsaturated soils the use of two independent stress variables: net stress and suction are needed. Suction values of TBJ “G” unit of the proximal facie were obtained using pressure plate, tensiometer and filter paper to obtain a Soil-Water Retention Curve (SWRC); the use of this curve into finite elements software can help to obtain the shear strength and permeability properties. For monitoring, the use of Quickdraw tensiometers (suction) and TMS3 (soil moisture content) is proposed, because it could be a way to build a field methodology for early warning system for the slopes for urban planning and risk assessment.},
     year = {2013}
    }
    

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  • TY  - JOUR
    T1  - Unsaturated Volcanic Tephra and Its Effect for Soil Movement in El Salvador
    AU  - José Alexander Chávez Hernández
    AU  - José Alexander Chávez Hernández
    AU  - Jiři Šebesta
    AU  - Lubomir Kopecky
    AU  - Reynaldo López Landaverde
    AU  - José Landaverde
    Y1  - 2013/04/02
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    N1  - https://doi.org/10.11648/j.earth.20130202.15
    DO  - 10.11648/j.earth.20130202.15
    T2  - Earth Sciences
    JF  - Earth Sciences
    JO  - Earth Sciences
    SP  - 58
    EP  - 65
    PB  - Science Publishing Group
    SN  - 2328-5982
    UR  - https://doi.org/10.11648/j.earth.20130202.15
    AB  - In El Salvador during the rainy season or when major earthquakes affect the area, processes like mass move-ments, liquefaction, erosion and floods affect the territory leaving environmental, social and economic damages. The vol-canic tephras called "Tierra Blanca Joven" (TBJ) which is a product of the last plinian eruption of the Ilopango Caldera are the more problematic region in the Metropolitan Area of San Salvador. In El Salvador during the summer and rainy season the groundwater level remains low in most of the areas, this means that the soils in the country are unsaturated and there are capillary forces that act on the soil structure making that an “apparent cohesion” (suction) improve the strength of the soil; this circumstance makes that the slopes are almost vertical and temporally stable, but will collapse when wetted or during seismic events. To that problematic is possible to add that the majority of the water pipelines are in bad condition and when they fail is possible to expect the collapse of entire streets or houses. Wetting of the soil is likely to occur following construction development, because evaporation is reduced by covering the ground surface with a structure. For unsaturated soils the use of two independent stress variables: net stress and suction are needed. Suction values of TBJ “G” unit of the proximal facie were obtained using pressure plate, tensiometer and filter paper to obtain a Soil-Water Retention Curve (SWRC); the use of this curve into finite elements software can help to obtain the shear strength and permeability properties. For monitoring, the use of Quickdraw tensiometers (suction) and TMS3 (soil moisture content) is proposed, because it could be a way to build a field methodology for early warning system for the slopes for urban planning and risk assessment.
    VL  - 2
    IS  - 2
    ER  - 

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Author Information
  • Department of Geotechnics, Faculty of Civil Engineering, Czech Technical University in Prague, ?VUT, Prague, Czech Republic

  • Department of Geotechnics, Faculty of Civil Engineering, Czech Technical University in Prague, ?VUT, Prague, Czech Republic

  • Department of Mechanics, Faculty of Civil Engineering, ?VUT, Prague, Czech Republic

  • Departamento de Recursos Naturales y Medio Ambiente, Facultad de Ciencias Agronómicas, Universidad de El Salvador, San Salvador, El Salvador

  • Departamento de Geotecnia, Escuela de Civil, Facultad de Ingeniería y Arquitectura, Universidad de El Salvador, San Salvador, El Salvador

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