Key geomechanical properties of the historically liquefiable TP-Lisbon sand

Abstract

The intrinsic properties of sands have a strong influence on the behaviour of these soils. Therefore, particle shape and granular packing can provide relevant insights into the mechanical properties of granular geomaterials. This study presents the characterisation of the key mechanical geomechanical properties controlling the behaviour of an alluvial fine sand, which composes the liquefiable layer of the geological profile at ‘Praça do Comercio’ square, located in the downtown of Lisbon (Portugal). For this purpose, a comprehensive experimental plan was conducted in the laboratory using accurate testing procedures. The experimental plan addressed: (i) the evaluation of the particle shape from a large number of particles using a computational geometry algorithm and statistical procedures; (ii) the estimation of the minimum and maximum void ratio through two standard methods; (iii) the assessment of the stress–strain behaviour by triaxial tests using lubricated end platens and an embedded connection piston, and void ratio measurements using end-of-test soil freezing; and (iv) the stress-dependency assessment of seismic wave velocities using bender elements. Results are interpreted within the critical state soil mechanics framework, highlighting the effects of the particle shape and granular package on the behaviour of this natural sand. In addition, critical state and small-strain parameters are compared and thoroughly discussed against selected data of other sands. Results provide experimental evidence about the influence of the particle shape and granular packing on the key geomechanical properties of TP-Lisbon sand.