Igari Takahiro

Study on effect of prevent liquefaction by compaction gravel pile

Ohtsuka Satoru

In the Great East Japan Earthquake that occurred in 2011, many liquefaction damage occurred in residential ground in inland areas and coastal areas. Liquefaction damage in the residential area will not result in loss of human life, but due to disruption of the lifeline and settlement of the house, it is put in a poor living environment. For this reason, highly reliable liquefaction countermeasure technology is also required for single-family houses targeting small-scale land. The liquefaction countermeasure by the screw press method developed by Grantec Co., Ltd. is expected to increase the density of the ground around the pile and to dissect pore water pressure by placing the gravel pile. Furthermore, it is possible to construct even in small places such as residential ground, and the use of natural materials reduces the burden on the environment, so the usefulness of the screw press method is expected.
At present, evaluation of the liquefaction countermeasure effect of the gravel pile takes into account only the compaction effect, and other liquefaction countermeasure effect is not considered. In the present study, field demonstration test and small model test were conducted for the purpose of examining the effect of liquefaction of gravel pile. From the field tests, it was shown that the gravel pile constructed by the screw press method has a compaction effect and the conversion N value of the surrounding ground rises. In the cone penetration test, the influence range of the compaction effect exerted by the gravel pile, the relation between penetration depth and penetration resistance was grasped and the effect of liquefaction countermeasure was confirmed by the shaking table model test. From the present study, it was shown that gravel pile having the compaction effect of the surrounding ground and the drainage effect is useful as liquefaction countermeasure.