Liquefaction Effects on the Northern Coronel Pier During the 2010 Maule Chile Earthquake

Abstract eng:
During the February 27, 2010 M w 8.8 Maule earthquake, soil liquefaction occurred at many sites; often leading to ground failure and lateral spreading. As a consequence, a variety of structures were severely damaged. Of special relevance were the effects of liquefaction on waterfront structures, which adversely affected the operation of some of Chile’s key port facilities. In this sense, lateral spreading and ground settlement damaged quay walls and pile-supported wharfs in older sections of both Valparaíso and San Antonio ports. Nevertheless, the most severe liquefaction-induced damage was found at Concepción and Coronel ports, causing important economic losses and downtimes to these facilities, and with direct costs associated to damage repairs of about US$ 300 million for the main ports in southern Chile. This paper focuses on the observed damage at the Northern Coronel Pier during the 2010 Maule Earthquake, which was strongly related to the soil characteristics at the port site. Available geotechnical information from both SPT and CPTu data, obtained before and after the earthquake, revealed the presence of medium dense to loose saturated sandy layers, at different depths, with a high liquefaction potential. In addition, low-to-negligible resistance mud sediments overlying the bedrock were identified, which could have worsen the effects of lateral spreading. The overall behavior for this case history is assessed using both a modified version of the simplified design procedure proposed in the MCEER/ATC-49-1 report and the design method for pile foundations in laterally spreading ground described in the 2011/04-PEER report. The residual lateral displacement is estimated by means of intersecting two curves: one that represents the lateral force-displacement curve of the structure stabilizing the sliding soils mass, and one that corresponds to the estimated residual displacements of the soil mass for different levels of restraining force. This approach gives permanent lateral displacements in the range of 50 to 120 cm, which is in good agreement with the observed behavior. From these results, design aspects such as the fixity conditions between pile heads and superstructure, the embedment depth of piles within the non-liquefied zone, and the number of piles along the longitudinal and transverse directions of the pier are discussed, and some preliminary conclusions and recommendations are elaborated.

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