- 期刊
麥寮砂動力夯實夯實擊效通之實驗研究
An experimental study on the effectiveness of dynamic compaction on Mal-Liao sands
摘要
動力夯實係將重錘以自由落體方式夯擊地表，可產生彈性波來改良深層砂土相對密度。根據彈性波理論推估表面波傳遞67%之夯擊能量，可是其對地盤改良並無益處；而實體波傳遞33%之夯擊能量，促使土壤顆粒排列趨於緊密，若能增加實體波傳遞能量之比例，應可有效地提升地盤改良效果。本研究使用室內動力夯實試驗儀及三種不同細顆粒含量之麥寮砂試體，進行動力夯實試驗，以探討細顆粒含量及夯錘錘底形狀對地盤改良效果之影響。試驗結果顯示，相較於平底夯錘，錐底夯錘夯擊後造成陷坑體積約多出5~25%。細顆粒含量愈高，陷坑體積愈大，電子圓錐貫入阻抗增加量皆愈高，而夯錘夯擊後夯擊點下方主要改良深度約為夯錘直徑之4倍。綜合而言，錐底夯錘之改良效果優於平底夯錘。
並列摘要
Dynamic compaction is a ground improvement method of increasing soil relative density by drop weights. When the drop weight impacts the ground surface, three types of elastic waves are generated. Surface waves are not useful for soil improvement, but shear waves and compression waves make soil fabric denser. Therefore, if the partition energy of compression waves and shear waves are increased, the effectiveness of ground improvement should be better. This study is mainly focusing on Mai-Liao sand samples of different fine contents and base-shapes of drop weights on the effectiveness of soil improvement. Compared with the flat-bottom drop weight, the laboratory dynamic compaction test results show that the conical-bottom drop weight produced a 5~25% more of crator volume. By using either type of drop weights, the increase in cone resistance is higher when the fine content is higher. Higher fine content is helpful in improving the influence zone. The effective depth of improvement is about 30cm, about 4 times of the diameter of the drop weight. According to the test results, the conical-bottom drop weight is better than the flat-bottom drop weight in the effectiveness of improvement.