Hollow cylindrical torsional shear test simulating stress history of sand compaction pile work history

The Sand Compaction Pile (SCP) method is a widely utilized ground improvement technology that enhances the density of the ground by constructing sand piles through penetration and repeated withdrawal/re-driving of a casing pipe. This method is the most widely used liquefaction countermeasure method in Japan. While the improvement effect of SCP is predominantly attributed to the resultant increase in soil density, recent studies have suggested that the stress history (such as increased lateral pressure and shear history) induced during the SCP work process also contributes significantly to its effectiveness. In order to more accurately reproduce the behavior of the ground during the construction of Sand Piles, the stress history simulating the SCP work process was applied to specimens in hollow cylindrical torsional shear tests, and the effects of the stress history were observed. The specimens were initially consolidated with a lateral stress ratio of 0.5 (K 0 = 0.5). Subsequently, a stress history including increased lateral stress and cyclic shear stress was applied. Finally, liquefaction resistance was assessed through cyclic loading. After applying the stress history, an increase in liquefaction resistance was observed in these specimens. This increase was larger than that of specimens subjected only to a lateral stress increase without the shear stress history. This increasing trend persisted even after the lateral stress was reduced following the application of stress history. Finally, these test results were analyzed to assess the impact of stress history on liquefaction resistance by comparing them with the relationship between relative density and the liquefaction resistance.