2021 Volume 16 Issue 4 Pages 333-342
The RL20,5% is generally used as the liquefaction strength of soil in Japan where the liquefaction is decided by basing on generated strain. However, when applying this method to evaluating the liquefaction strength of the ground improved by the permeable grouting method, the method may not fully evaluate the characteristics of the improved soil including the toughness against cyclic shearing load and the suppression of residual deformation. In this study, a series of cyclic torsional shear tests on the hollow cylinder specimen of improved ground with the permeable grouting method were conducted at a high shear stress ratio assumed with a strong earthquake. By observing its resistance against cyclic shear load, it was found that in order to appropriately evaluate the characteristics of improved soil, it is necessary to decide the liquefaction strength by considering both the strain and the excess pore water pressure. In addition, even when the soil is judged as non-liquefied soil, its excess pore water pressure still increases under cyclic shear load. Therefore, by confirming the undrained strength deformation characteristics of the improved ground at a high water-pressure state after a cyclic shear load, the undrained shear strength of improved soil was confirmed the same with that before applying the cyclic load.
