夯實的成效受到土壤種類、含水量及夯擊方式等因素影響。一般現地施工須檢驗土壤之乾單位重是否合乎施工規範要求，常以工地密度試驗作檢驗，此法雖已廣泛被接受，但在實際檢驗上仍有許多不便之處，檢驗過程繁雜且缺乏便利性。本研究主要目的為藉由夯擊試驗，希望能探討一新的檢測方法。夯擊試驗採用特製夯擊試驗儀，將加速度計裝置於夯錘上，再利用夯錘夯擊試體，即可測得加速度歷時曲線，此曲線之最大值即為衝擊加速度(impact acceleration, )。本研究以中大紅土為試驗土樣，利用夯擊試驗探討夯實曲線之乾側在相對夯實度為90-100％時，試體承受夯擊後所激發之衝擊加速度與含水量、乾單位重及夯擊落距之關係。試驗結果顯示，在各種夯實能量條件下，衝擊加速度與乾單位重間皆呈線性關係，以夯實能量對衝擊加速度加以正規化，二者間仍有良好的線性關係，由衝擊加速度配合此正規化後之回歸式可求得夯實土壤乾單位重。為了探討相關剪力強度特性，另行製作相同條件的試體進行圓錐貫入試驗，分析錐尖阻抗與衝擊加速度之關連性，所得之錐尖阻抗與乾單位重間之關係與前述之衝擊加速度與乾單位重之關係類似，且衝擊加速度與錐尖阻抗間存有良好的線性關係。 Soil type, moisture content, compaction methods and other factors will affect the effectiveness of compaction. In order to measure the dry unit weight of soil in field, the sand cone method or the rubber balloon method are used frequently, but those are still not convenient enough. The purpose of this study is to explore a new detection method by impact test. The impact test uses a special test apparatus, by setting an accelerometer on the hammer, the variation of acceleration during the impact of hammer can be measured. The peak value of acceleration in the acceleration time history is defined as Impact acceleration. In this study, the lateritic soil sampled from NCU campus was used in the tests. The engineering properties of soil in the dry side and within 90-100% of the relative compaction is examined to obtain the relationships among impact acceleration, moisture content, dry unit weight and impact height. These experimental results revealed that under various conditions of compaction energy, the impact acceleration and the dry unit weight has a linear relationship. If the impact accelerations is normalized by compaction energy, these two factors will still have a good linear relation. Therefore, by using the data of impact acceleration, the dry unit weight of compacted soil can be obtained. Furthermore, prepared some specimens with the same conditions to perform the cone penetration tests, and the relationships between cone resistance and impact acceleration were examined. The relationships between cone resistance and dry unit weight are similar to that of the acceleration and dry unit weight. Acceleration and cone resistance have a linear relationship also.
