Study of the static and seismic performance of a geogrid reinforced soil wall as bridge abutment in Concepción

Abstract

espanolEl terremoto del 27 de febrero 2010 en Chile central y sur fue una prueba muy intensa para las soluciones con muro de suelo reforzado recientemente construidas como estribos de puente. Este terremoto de subduccion de magnitud momento 8.8 causo graves danos a varios muros de hormigon armado tradicionales para estribos de puentes. Sin embargo, no se registro mayor dano en soluciones relativamente nuevas y reforzadas con geosinteticos. Por esta razon, es importante revisar el diseno y construccion empleada en estos proyectos. Para este fin, se describe y estudia un caso representativo ubicado proximo al epicentro. Ademas, se entrega informacion sobre los suelos de fundacion, diseno y secuencia constructiva de los refuerzos de geosinteticos usados en los estribos de puente. Los suelos de fundacion eran desfavorables, correspondiendo principalmente a depositos fluviales y marinos proximos al cauce y desembocadura del rio Andalien. El analisis incluye la verificacion de la estabilidad estatica y sismica, tanto externa como interna. Tambien se realizan analisis de estabilidad global estatica y sismica. Los metodos usados en los analisis son equilibrio limite y pseudo estatico segun las recomendaciones de FHWA. Resultados muestran que el diseno fue adecuado para soportar un evento sismico tan fuerte en terminos de estabilidad interna y externa. No obstante, se encontro que la presencia de pilotes prevenia una falla sismica global del muro de suelo reforzado con geomallas como estribo de puente. Se realizan comentarios y observaciones finales relacionados con el diseno y construccion que podrian explicar la respuesta favorable de las estructuras reforzadas con geosinteticos sometidas a este fuerte terremoto de subduccion. EnglishThe 27th February 2010 earthquake in central and south of Chile was a very strong test for recently constructed geosynthetics reinforced soil wall solutions as bridge abutments. This 8.8 moment magnitude subduction earthquake caused severe damage to several traditional reinforced concrete walls for bridge abutments. However, no significant damage was found in relatively new geosynthetics reinforced solutions. For that reason, it is important to review the design and construction employed in these projects. To this end, a representative case located close to the epicentre is described and studied. Moreover, information is provided regarding the foundation soils, design and construction sequence of the geosynthetics reinforcement used for bridge abutments. The foundation soils were poor, corresponding mainly to marine and fluvial deposits close to the stream and mouth of the Andalien River. The analysis covers the verification of static and seismic external and internal stability. In addition, global static and seismic analyses are carried out. The methods used for the analyses are limit equilibrium and pseudo-static following recommendations of the FHWA. Results show that the design was adequate to cope with such a strong seismic event in terms of external and internal stability. Nevertheless, it was found that the inclusion of piles prevented a global seismic failure of the geogrid reinforced soil walls as bridge abutment. Final comments and remarks are presented related to design and construction which may explain the favourable performance of geosynthetics reinforced structures under this strong subduction earthquake.