Abstract
A chain event of the 2016 Kumamoto earthquakes caused considerable geotechnical damage related to liquefaction in many places around Kumamoto plain. Many low-rise houses and traditional Japanese style houses, which were constructed on shallow foundation, suffered differential settlement and tilting due to liquefaction. To mitigate the building damages due to the liquefaction, a new countermeasure method of jet grout grid form with a horizontal slab is introduced in this study. The effectiveness of the proposed technique was evaluated through physical modelling and numerical modelling. As a part of the physical modelling, a set of 1 g shaking table tests for unimproved case and improved case were performed, in which the mitigation effects of the grid form with a horizontal reinforcing slab were examined based on the acceleration, excess pore water pressure ratio as well as ground settlement. Numerical simulation was also performed for assessing the effect of improved method on soil-structure interaction and building settlement during the earthquake. The physical and numerical results confirmed that the grid form with horizontal slab reinforced method is effective in settlement control and offers favorable contribution in liquefaction mitigation.
Highlights
As a part of the physical modelling, a set of 1 g shaking table tests for unimproved case and improved case were performed, in which the mitigation effects of the grid form with a horizontal reinforcing slab were examined based on the acceleration, excess pore water pressure ratio as well as ground settlement
A new countermeasure technique of grid form with horizontal slab was introduced and its effectiveness in liquefaction mitigation was assessed by experimental modeling and numerical modeling
2) The relatively small built up of excess pore water pressure in the soil within the grid form compared to the unimproved case shows that the use of grid spacing ratio 0.2 in a new improved method is effective in liquefaction mitigation
Summary
A chain of earthquakes triggered significant damage to infrastructures including the renowned cultural heritage of Kumamoto castle, buildings, roads and river embankments. Several traditional Japanese style houses and low-rise buildings suffered differential settlement and tilting as the consequences of liquefaction in those areas. A new private hospital in Hirata district of Minami ward was one of the most affected buildings due to liquefaction. According to the Kumamoto City report, approximately 2900 buildings suffered severe damage caused by liquefaction during the 2016 Kumamoto earthquake [2]
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