The objective of this study was to clarify the effect of lattice-arranged gravel on the liquefaction characteristics of sandy soil because it was considered that the liquefaction strength increases when gravel is placed vertically into sandy soil. Liquefaction tests by torsion shear tests and two-dimensional liquefaction analysis were carried out at various gravel insertion rates. From a series of tests and analyses, as the gravel insertion rate increased, the occurrence of double amplitude shear strain and residual excess pore water pressure ratio was suppressed. When the number of cycles was small, the amount of shear strain and residual excess pore water pressure increased per a wave decreased as the gravel insertion rate increased, and there was no significant difference in the amount of these increases when the number of cycles increased. For the gravel insertion rates greater than 10%, the liquefaction strength increased proportionally with increasing gravel insertion rate. These results suggest that placing gravel in a grid pattern within sandy ground can be an effective countermeasure against liquefaction, improving the ground.
