Cyclic DSS tests for the evaluation of stress densification effects in liquefaction assessment

• 86 Cyclic Direct Simple Shear (Cyclic DSS) tests with Ain Beniam and Coimbra sands.
• Distinct initial void ratios and initial conifining stresses were applied, contractiveness was observed to decrease with initial confining stress.
• A densification effect is responsible for this increasing contractiveness with increasing initial confining stress.
• The densification effect can be explained by the reconstitution method.
• The densification effect can be also explained by the plastic strain accumulation during the test.

To evaluate the stress correction factor for the Cyclic Resistance Ratio (“CRR”) under cyclic loading with principal stress rotation, 86 Cyclic Direct Simple Shear (CDSS) tests were performed on two sands, one from Ain Beniam, in Alger, Algeria, and another from Coimbra, Portugal. These sands have distinctive grain shapes and size distributions and were tested with various relative densities and under different initial effective confining stresses. The results of the tests performed with zero initial static shear stress – therefore with the static shear stress factor Kα equal to one – indicate that the values of confining stress level correction factor, Kσ, as currently recommended, seem to underestimate the cyclic resistance.