Análisis paramétrico de la Influencia de las variables geotécnicas en la definición de soportes y refuerzos para túneles
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Carrillo Cedeño, Jorge Luis
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Trabajo de grado - Maestría
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EspañolFecha de publicación
2019-02-08
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Las excavaciones subterráneas en nuestro entorno han ido en aumento, anteriormente con énfasis en proyectos de minería y generación de energía, y más recientemente, en túneles viales. Tal uso se encuentra asociado a acortar distancias, mitigar el impacto del invierno en corredores viales o evitar problemas geotécnicos. El proceso de construcción de túneles necesita, además, una correcta selección del método de excavación y soporte y/o refuerzo a implementar, por su gran importancia para la estabilidad de la excavación. En este sentido hoy se presentan inconvenientes en la manera de clasificar durante construcción el macizo rocoso con el fin de decidir el tipo de tratamiento, ya que tiende a ser más por el criterio en campo del diseñador, haciendo uso de su posición dominante, que por el de las otras partes involucradas (interventoría y contratista), de tal manera que es posible que para varios diseñadores se tendrían diferentes tipos de clasificación del mismo macizo. Dado que para cada proyecto se han definido varios tipos de terreno se considera de suma relevancia poder realizar esta selección de manera más objetiva. En este documento se plantea una metodología para la selección del tipo de soporte con base en la predominancia de las variables geotécnicas y su influencia en el comportamiento esfuerzo-deformación de la excavación. La metodología se fundamenta en el análisis paramétrico a una sección de un túnel vial de hastiales verticales y bóveda circular. En el análisis se utiliza el programa de elementos finitos Phase2 y el criterio de falla de Hoek y Brown. Se demuestra que el comportamiento de la excavación es influido por la extensión de la zona más débil, criterio que debe considerarse en la selección en campo del soporte a implementar. La metodología se considera de gran utilidad y se muestra que es posible preparar para cada proyecto, durante el proceso de diseño, una ayuda o manual para la selección del tipo de soporte.
Abstract: Use of underground excavations in Colombia is increasing. Before, use was associated mostly to mining and hydro projects and more recently, in road projects. Such use is associated to either shorten distances, reduce susceptibility to interruption in winter periods or avoiding sites with stability problems. The tunneling process requires of an appropriate selection of the excavation and reinforcement method because the relevance for stability. In this regard, difficulties arise during construction in the way rock mass is classified in order to decide support to be installed. Generally, the designer makes such decision taking advantage of a dominant position, while contractor and supervision recommendations are not considered. Since several rock mass qualities and support schemes exist in each project, it is considered of most relevance to be able to select the appropriate support on a more objective way. In this document, a methodology for field support scheme selection based on predominance of geotechnical variables and its influence in the stress deformation behavior of the excavation is proposed. The basics of the methodology is a parametric analysis of a D-shape tunnel. The Phase2 computer program and the Hoek and Brown failure criterion were used for the analysis. It is shown that tunnel excavation behavior is affected by the amount of the weakest material existing in the perimeter of the tunnel as compared to strongest one. Therefore, such aspect must be considered for field selection of support scheme. The methodology can be very useful during tunnel construction so, for each project, a support selection aid manual should be prepared as part of design.
Abstract: Use of underground excavations in Colombia is increasing. Before, use was associated mostly to mining and hydro projects and more recently, in road projects. Such use is associated to either shorten distances, reduce susceptibility to interruption in winter periods or avoiding sites with stability problems. The tunneling process requires of an appropriate selection of the excavation and reinforcement method because the relevance for stability. In this regard, difficulties arise during construction in the way rock mass is classified in order to decide support to be installed. Generally, the designer makes such decision taking advantage of a dominant position, while contractor and supervision recommendations are not considered. Since several rock mass qualities and support schemes exist in each project, it is considered of most relevance to be able to select the appropriate support on a more objective way. In this document, a methodology for field support scheme selection based on predominance of geotechnical variables and its influence in the stress deformation behavior of the excavation is proposed. The basics of the methodology is a parametric analysis of a D-shape tunnel. The Phase2 computer program and the Hoek and Brown failure criterion were used for the analysis. It is shown that tunnel excavation behavior is affected by the amount of the weakest material existing in the perimeter of the tunnel as compared to strongest one. Therefore, such aspect must be considered for field selection of support scheme. The methodology can be very useful during tunnel construction so, for each project, a support selection aid manual should be prepared as part of design.