土样制备对自由膨胀率的影响及其改进方法

着重论述了土样制备对自由膨胀率试验成果的影响。试验研究发现，3种口径（4.5，5，5.5 mm）和3种下落高度(5，10，15 mm)对取土质量和试验结果影响不大，但颗粒粉碎程度的影响非常明显。规程中土颗粒过0.5 mm筛的规定不够完善，在此粒径范围内3种粒组（0.25～0.5，0.1～0.25，<0.1 mm）的土样，其自由膨胀率结果存在差异。其中，前两者差别不大，<0.1 mm粒组土样的试验结果一般较前两者低30 %～45 %，与膨胀土其他属性指标不匹配。研究结果表明：不同粒径土样在10 mL量土杯中质量相差多达2 g，取土质量是影响自由膨胀率结果的主要因素之一，颗粒结构变化也有可能是影响因素之一，建议土样粒径范围为0.1～0.5 mm。

Effect of soil sample preparation on free swelling ratio and its improved measures

Free swelling ratio is a significant index for classification of expansive soil and identification of swelling potential. Unfortunately it is influenced by many factors, among which the effect of soil sample preparation is discussed. Test researches show that soil sampling mass and test results is of little influence by three funnel bores(4.5, 5, 5.5 mm) and three drop heights (5, 10, 15 mm) while they are much influenced by degree of grinding of soil. The specified standard that soil particle size is less than 0.5 mm is not perfect and the results of free swelling ratio for three soil particle sizes(0.25－0.5, 0.1－0.25, <0.1 mm) is widely variable, it is discovered that the finest soil(<0.1 mm) is reduced by 30 %－45 % and isn’t consistent with other indexes for expansive soil classification. The contrast is studied and mass difference of particle up to 2 g measured by a cup of 10ml is found; the conclusion that the results is influenced by particle mass is established and the changing of structure is a possible reason. At last the particle size between 0.1 mm and 0.5 mm is suggested.