Evaluating liquefaction resistance and initial shear modulus considering particle orientation of sand

This study using triaxial tests with bender elements (BEs) and optical microscopy specifically examined liquefaction and reliquefaction mechanisms inferred from sand particle orientation. Anisotropic specimens were extracted at different depositional angles (0°, 45°, and 90°) from the soil blocks created using air pluviation (AP) at relative density ( D r ) of 60 %. Liquefaction resistance (CRR 1 ) tended to be greater for higher orientation angles, with the greatest CRR 1 obtained for 90° specimens. By contrast, reliquefaction resistance (CRR 2 ) showed an increasing trend for 0° and 45° specimens, but a decreasing trend for the 90° specimen compared to CRR 1 . The initial shear modulus ( G 0 ) was greater for higher particle orientation angles. Because of liquefaction, significant increases in G 0 were found for 0° and 45° specimens, but only slight increases for the 90° specimen, attributed to a 2.04–3.05 % increase in D r . The sand particle orientation was evaluated based on 2D optical microscopic measurements and mathematical estimation of the orientation. Liquefaction caused particle reorientation: an increase in the average orientation angle for the 0° and 45° specimens, but a slight decrease for the 90° specimen. Results show that the change of CRR and G 0 was explained well according to the change of particle orientation. • Triaxial tests of sand elucidated liquefaction and reliquefaction mechanism. • 2D microscopic analysis revealed particle reorientation before/after liquefaction. • CRR and G 0 showed strong connection with sand particle orientation. • CRR and G 0 were highest at 90° and lowest at 0 o orientations at first liquefaction. • Particle reorientation during first liquefaction affects reliquefaction behavior.