Comportamiento sísmico de taludes sobre suelos potencialmente licuables mejorados mediante columnas de grava
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Fecha
2017
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es
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Universidad Andrés Bello
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Licencia CC
Licencia CC
Resumen
Uno de los principales objetos de estudio de la ingeniería geotécnica sísmica es el comportamiento de estructuras apoyadas sobre suelos potencialmente licuables. Una forma de hacer frente al riesgo de licuefacción es utilizar los denominados métodos de mejoramiento de suelo, los cuales tienen por objeto ya sea (i) densificar el terreno, (ii) ayudar a mejorar las condiciones de drenaje del suelo, y/o (iii) ayudar a reducir el nivel de solicitaciones de corte inducidas en el terreno producto del sismo. En Chile, el método más utilizado es el de vibro-sustitución por columnas de grava, que permite el reemplazo parcial del terreno existente por una serie de columnas de agregado grueso, de alta trabazón mecánica, rodeadas por el suelo adyacente que se densifica durante el proceso constructivo. Si bien este tipo de soluciones permite reducir el potencial de licuefacción del terreno, se desconoce a priori cuál podría ser el desempeño sísmico de la estructura apoyada sobre el material mejorado; por ejemplo, en términos de fuerzas o desplazamientos inducidos por sismo, lo que dificulta evaluar su eficiencia respecto a otras alternativas de mejoramiento.
En este trabajo se estudia el comportamiento sísmico de taludes arenosos construidos sobre suelos potencialmente licuables que han sido mejorados mediante columnas de grava. Utilizando métodos tradicionales de estabilidad de taludes y análisis basados en el concepto del bloque deslizante de Newmark, se evalúa el rango de desplazamientos típico que podrían inducir los terremotos de subducción chilenos para diferentes configuraciones tanto del terreno a mejorar como de la solución de columnas de grava adoptada.
A partir de los resultados obtenidos, se entregan conclusiones y recomendaciones generales para el diseño sísmico de taludes que deban apoyarse sobre suelos susceptibles de experimentar licuefacción durante sismos severos, y también se discute la efectividad del uso de columnas de grava en la reducción de los desplazamientos sísmicos inducidos en este tipo de estructuras de tierra.
One of the main purposes of geotechnical earthquake engineering is the behavior of structures on potentially liquefiable soils during large earthquakes. One way to mitigate the effects of soil liquefaction is to make use of the so-called ground improvement methods, which are intended to either (i) densify the soil, (ii) help improving soil drainage conditions, and/or (iii) help reducing the level of shear stresses induced in soil by the earthquake. In Chile, the most commonly used method is vibro-replacement by gravel columns, which allows a partial replacement of the existing soil by a series of coarse aggregate columns with high mechanical resistance, surrounded by the adjacent soil that is densified during the construction process. Although it is known that these type of solutions allow to reduce the liquefaction potential of the soil, it is unknown beforehand what the seismic performance of the structure on the improved material could be; for example, in terms of forces or displacements induced by the earthquake, which makes it difficult to evaluate their efficiency compared with other improvement alternatives. In this work we study the seismic behavior of sandy slopes built on potentially liquefiable soils that have been improved by gravel columns. Using traditional methods of slope stability and analyses based on the Newmark Sliding Block method, the typical range of displacements that Chilean subduction earthquakes could induce are evaluated for different configurations of both the ground to be improved and the gravel column solution adopted. Based on the results obtained, general conclusions and recommendations are given for the seismic design of slopes to be built on soils susceptible to liquefy during severe earthquakes and also the effectiveness of the use of gravel columns on the reduction of induced seismic displacements is discussed.
One of the main purposes of geotechnical earthquake engineering is the behavior of structures on potentially liquefiable soils during large earthquakes. One way to mitigate the effects of soil liquefaction is to make use of the so-called ground improvement methods, which are intended to either (i) densify the soil, (ii) help improving soil drainage conditions, and/or (iii) help reducing the level of shear stresses induced in soil by the earthquake. In Chile, the most commonly used method is vibro-replacement by gravel columns, which allows a partial replacement of the existing soil by a series of coarse aggregate columns with high mechanical resistance, surrounded by the adjacent soil that is densified during the construction process. Although it is known that these type of solutions allow to reduce the liquefaction potential of the soil, it is unknown beforehand what the seismic performance of the structure on the improved material could be; for example, in terms of forces or displacements induced by the earthquake, which makes it difficult to evaluate their efficiency compared with other improvement alternatives. In this work we study the seismic behavior of sandy slopes built on potentially liquefiable soils that have been improved by gravel columns. Using traditional methods of slope stability and analyses based on the Newmark Sliding Block method, the typical range of displacements that Chilean subduction earthquakes could induce are evaluated for different configurations of both the ground to be improved and the gravel column solution adopted. Based on the results obtained, general conclusions and recommendations are given for the seismic design of slopes to be built on soils susceptible to liquefy during severe earthquakes and also the effectiveness of the use of gravel columns on the reduction of induced seismic displacements is discussed.
Notas
Tesis (Ingeniero Civil)
Palabras clave
Diseño Antisísmico, Taludes (Mecánica de Suelos)