Kurita Shuhei

An Experimental study on  Quantitative Evaluation of liquefaction countermeasure effectiveness using Gravel piles

Ohtsuka Satoru

In the Great East Japan Earthquake that occurred in 2011, many liquefaction damage occurred in residential areas in inland areas and coastal areas. Therefore, we can say that measures to liquefaction of residential ground are important in the future. In the case of large scale target such as infrastructure, design guidelines for liquefaction countermeasures have already been established. However, since the residential ground is small, it is difficult to implement countermeasures using conventional design guidelines. Therefore, design guidelines appropriate for single-family homes for small-scale land are required. In this research, we focused attention on the gravel pile construction method as a countermeasure for liquefaction of residential ground. The gravel pile is expected to have structural effect by compaction effect, pore water pressure dissipation effect, rigidity. However, at present, evaluation of the liquefaction countermeasure effect of gravel pile takes into consideration only compaction effect, and other liquefaction countermeasure effect is not taken into consideration. In this research, we conducted a cone penetration test and a shaking table model test to clarify the effect of liquefaction of gravel pile and to construct design guidelines. From the cone penetration test, the influence range of the compaction effect by the gravel pile, the relationship between penetration depth and penetration resistance was grasped. Moreover, it was found that it is difficult to obtain the improvement effect in the shallow part of the improved ground, and the compaction effect of the gravel pile can be managed by the improvement ratio by area ratio. Furthermore, from the vibrating table model test, it became clear that the effect of liquefaction countermeasure is larger for deeper part and smaller for shallow part.