Fumiya SASAGAWA

Laboratory and Field Tests on the Compaction Effect of Gravel Piles on Sandy Soil

Satoru OHTSUKA

Liquefaction of residential soil is a natural disaster that causes severe damage to building foundations, often resulting in total destruction. In this study, we focused on the gravel pile (GP) method because it is inexpensive and easy to construct in narrow areas, and attempted to quantitatively evaluate the improvement effect and establish a design method. In this study, laboratory shake table tests, laboratory cone penetration tests, and field demonstration tests were conducted. The results of this study are presented below. First, the indoor shaking table test confirmed that the compaction effect had the greatest influence on the liquefaction countermeasure effect of GP. Next, small cone penetration tests on model ground showed that the improvement effect can be organized by the improvement ratio regardless of the pile diameter, and that the limit of improvement effect in the case of high initial relative density was shown. Furthermore, field demonstration tests were conducted to generalize the results of the laboratory tests to full-scale design. However, the results of the laboratory tests were inconsistent and difficult to sort out, as they did not show sufficient improvement. In this study, considering that the test site is a riverbed and the results of the cone penetration test are affected by the river water level fluctuation, small cone penetration tests were conducted on a model ground with a history of water level change. The results suggest the possibility of underestimating the effectiveness of improvement when the improvement is made.