|Budget Amount *help
¥4,700,000 (Direct Cost : ¥4,700,000)
Fiscal Year 1996 : ¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1995 : ¥2,900,000 (Direct Cost : ¥2,900,000)
Heavy tamping is one of ground improvement technique for loose sandy ground and gravelly and rock waste fill. This method generally aims at uniformly compacting the whole ground, however, we found that a high density compacted area bulbously grew up beneath the tamping point by ram blow. The purpose of this study is to investigate the development and application of 'Compacted Bulb Foundation Method', which applies heavy tamping to the spread foundation. A series of centrifuge model tests was carried out to investigate effects of ram mass, ram base area, number of blows, number of passes and foundation base area on characteristic of bearing capacity of compacted dulb foundation.
Main conclusions are : 1)ultimate bearing capacity of compaction bulb foundation increases more than 200 times and coefficient of subgrade reaction increases the number by 10 times in comparison with initial ground, 2)under ram mass less than 20t, the ground tamped by ram having large base area than that of foundation denotes large bearing capaci, 3)inversely, under ram mass more than 40t, ground tamped by ram having large base area than that of foundation denotesless bearing capacity, but this tendency can guess that degree of compaction of backfilling is small, 4)larger base area of ram can have high bearing capacity under the same ram mass. From these results, a design procedure of this method using the coefficient of subgrade reaction and the allowable settlement was proposed.