摘 要 本研究係對砂土試體進行圓形土槽模擬夯擊試驗，探討砂土受夯擊時垂直動應力影響之範圍，以期對動力夯實工法施工時土壤之力學行為有更進一步的瞭解。 於實驗中利用圓形土槽模擬夯擊試驗，夯擊不同相對密度之乾砂，在變換不同夯錘半徑及不同夯擊能量，包含不同夯錘質量及落距情況下，求出砂土承受夯擊瞬間，土層中之動應力分布圖，經由此動應力分布圖，期能定出較理想之無因次影響深度及寬度之值。此外，針對土層在受夯擊時產生沉陷值進行量測，探討陷坑所損耗能量與實際夯擊能量之比。 由試驗結果得知，砂土層中垂直動應力和衝擊荷載兩者之比值關係，在不同條件的情況下，如夯錘半徑、落距、夯錘質量及夯擊次數，趨勢大致相同，惟相對密度對垂直動應力和衝擊荷載兩者之比值有所影響，相對密度愈大，垂直動應力和衝擊荷載兩者之比值也愈大，表示能量能傳遞至更深層的土層中，能量於土層中消散的速度較緩慢。另外，集中因子ν隨土層深度加深有減小之趨勢，隨相對密度增加有增大之趨勢，但受夯錘質量及落距等之影響則不明顯。 ABSTRACT In this research, to understand soil mechanical behaviors under dynamic consolidation method, dynamic compaction model tests in circular chamber were conducted to investigate the vertical dynamic stress influence range on sand. Using dynamic compaction model tests in circular chamber to get the distribution graph of dynamic stress under the situation of changing different relative density, radius of hammer and impact energy which include the different mass of hammer and dropping distance. The value of no dimension depth and width can be test out by the distribution graph of dynamic stress. Moreover, to discuss about the ratio between the energy lose of crater and the real impact energy by measuring the depth of crater. It can be found that the ratio between vertical dynamic stress and impact load are tend to be the same under the different situation as radius of hammer, dropping distance, mass of hammer and impact number from this research. Only relative density affects the ratio between the vertical dynamic stress and impact load. The bigger relative density is, the bigger ratio between the vertical dynamic stress and impact load could be. It proves that the energy can be spread to the deeper layer of sand and dismissed slowly. Besides, the factor of concentration is going to decrease with the depth of sand increasing but to increase with the relative density increasing. However, it is not so obviously for the factor of concentration to be affected by mass of hammer and dropping distance.
