Liquefaction resistance of TP-Lisbon sand: a critical state interpretation using in situ and laboratory testing

Abstract

This paper describes a comprehensive characterisation of liquefaction resistance of a sandy soil collected from the 'Terreiro do Paco' in the historical centre of Lisbon (Portugal), denominated as TP-Lisbon sand. This natural sand has experienced earthquake-induced liquefaction caused by the 1755 earthquake. The characterisation was carried out by combining in situ with laboratory tests. The results of in situ tests allowed obtaining the factor of safety profiles against liquefaction, liquefaction potential index and liquefaction severity number. On the other hand, an experimental programme conducted in the laboratory allowed defining the cyclic resistance ratio for different relative densities and mean effective stresses of TP-Lisbon sand. Besides, the effects of inversion and rotation of principal stresses on liquefaction resistance were examined by advanced testing procedures (i.e. cyclic triaxial and cyclic direct simple shear tests). The results of this study were analysed within the critical state soil mechanics framework by comparing the state parameter reported by in situ and laboratory testing, particularly when using remoulded soil specimens. The data presented in this study provide a database for numerical analyses and cyclic or seismic geotechnical design, following a framework appropriate to natural sands susceptible to liquefaction phenomena.