標準夯實試驗最佳含水量與最大乾密度不確定性之研究

本研究針對土壤含水量與密度關係，使用標準式夯實試驗在相同夯壓能量12400ft-1bf/ft3條件下，執行Method-C；以4英吋鋼模用5.5磅夯錘自由落距12英吋分三層夯打試體每層夯打25下，及Method-D；以6英吋鋼模5.5磅夯錘自由落距12英吋分三層夯壓試體每層夯打56下，Method–C與Method-D各求得土壤之最大乾密度與最佳含水量之差異性，作為土木工程測試領域實驗室在求取現場土壤壓實度試驗時，在執行土壤含水量與密度關係試驗選用Method-C及Method-D之參考性指標。研究中以CNS15305（2011）標準選取適當土壤級配粒料作為試驗用樣本，並依據CNS11777（2005）及CNS5091（1986）兩項中華民國國家標準方法進行試驗，分別將Method–C與Method-D各進行30組試驗，並將求得試驗數據依照量測不確定度評估模式，各別計算出在不同標準夯實試驗Method–C與Method-D所求得土壤之最大乾密度與最佳含水量，並說明當量測信心水準95%時使用擴充係數k=1.96計算出擴充不確定度數值，以分析土壤之最大乾密度、土壤最佳含水量之量測數據的離散程度。利用量測不確定度評估模式分析，計算各求得土壤最大乾密度、土壤最佳含水量之量測不確定度數值，依據所得試驗數值的擴充不確定度，判斷分析計算求得Method–C土壤最佳含水量與土壤最大乾密度，擴充不確定度分別為 0.15%、 20㎏/m3，而Method–D分別為 0.10%、 9㎏/m3，可得知Method–C的擴充不確定度較Method–D大，其分析原因最主要為人員操作變異性與使用6in及4in模具相關，進行試驗操作時有ㄧ定程度的誤差存在，故分析二者試驗法的差異性及準確度，藉以提供實驗室人員在執行道路鋪面土壤級配料壓實度品質控制時，依工程性質選用Method–C或Method-D執行土壤含水量與密度關係試驗的參考指標。

關鍵字

土壤最大乾密度；土壤最佳含水量；量測不確定度評估模式；碎石級配材料

並列摘要

This study intends to investigate the relationship between soil moisture and density. Under the sameenergy 12400ft-1bf/ft3 ram pressure conditions. We used the standard compaction test to implement Method-C (Using 5.5 1bs hammer free-falls from the 12 inch height to 4 inch steel specimens which is divided into three-tiers. Each tier pounds 25 times). and Method-D(Using 5.5 1bs hammer free-falls from the 12 inch height to 6 inch steel specimens which’s divided into three-tiers. Each tier pounds 56 times). The difference of the maximum dry density and the difference of the optimum moisture content between C and D. Would be the references to choose in the laboratory. In this study, the sample test was adopted with CNS 15305 (2011) Materials for Soil-Aggregate, and use CNS 11777 (2005) and CNS 5091 (1986)-two methods of Chinese national standard test. Each made 30 groups of experimences. According to the meacurement uncertainty assessment model. We used test data and the standard effort methods C and D to calculate the maximum dry density and optimum moiseure content. Based on the measured equivalent 95% confidence level and using the expansion coefficient k=1.96. We calculated the numerical expansion of uncereainty, and the dispersion measures of soil’s maximum dry density and optimum moisture content. We obtained the result was that the measured-uncertainty mode of the optimum moisture content and the maximum dry density of soil in Method-C were 0.15% and 20 kg/m3 respectively；in Method-D were 0.10% and 9 kg/m3 respectively. We got the measured- uncertainty mode of Method-C was bigger than that of Method-D. We considered that the reasons were related to the operational difference and using different molds (6in and 4in). Therefore, we analyzed the accuracy and difference between C and D, than the resutes of this study may be treated as an index for choosing Method-C or Method-D in the laboratory.