DEVELOPMENT OF A NEW FRACTURING GROUTING WITH LEAF VEIN SHAPE GROUT FOR SOIL LIQUEFACTION COUNTERMEASURE

The authors have proposed a new fracture grouting method, which can increase densities of liquefiable ground and increase liquefaction resistance by injecting leaf vein shape grout. Since this method can im-prove liquefiable ground effectively with low grouting ratio (approximately 10% in volume ratio), widely spreading liquefiable ground can be improved economically within a short period. This paper describes results of experimental studies following brief explanation about a concept of the propose method. At first, 4 cases of trial grouting tests were conducted to validate feasibility of the proposed grouting method using a large-scale soil stratum pit. As a results, it was confirmed that leaf vein shape grout could be injected in loose saturated sand ground by a dynamic grouting method, of which specifications were adequately set. Furthermore, increase in density of the improved ground could be evaluated by some soil investigations conducted before and after grouting, such as the standard penetration test, the in-situ seepage test, the PS logging and so on. Finally, a series of shaking table tests were conducted to confirm effect of the proposed method against soil liquefaction during earthquakes. The test results clarified that the loose liquefiable sand ground could be effectively improved by the proposed method and could show almost the same liquefaction resistance with that of the dense sand ground, which was ideally compacted to have the same density as-sumed in the improved ground.