Liquefaction assessment CPTu tests in a site in South of Portugal

The Algarve is a province in the South of Portugal located near the E-W Eurasia-Africa plate boundary and is characterized by a moderate seismicity, with some significant historical earthquakes causing important damage and economical losses. Besides the effects of large plate boundary events the region also suffers the impact of local onshore moderate-sized earthquake sources. The seismic hazard evaluation and mitigation of the area is therefore very important for the local populations and the large number of tourists that visit the region every year. This paper focuses on the assessment of the liquefaction potential of the site. The study was based on results of CPTu tests that were performed to estimate the cyclic resistance ratio (CRR) from in situ geotechnical investigation, and to compare it with the cyclic stress ratio (CSR), evaluated by considering the values proposed in the Eurocode (EC-8) for Algarve. These two parameters were used to determine the safety factor (FSliq) against liquefaction and the liquefaction potential index (LPI). In addition, the liquefaction severity number (LSN) was also used to quantify the effects of liquefaction and consequently the local area prospective damage estimated from the volumetric strains derived from CPTU data interpretation.