本文通过室内无荷膨胀率试验，对宜昌市某一级公路改建工程项目路段的膨胀土进行了研究。重点分析了无荷膨胀率与时间、掺砂比例、初始干密度之间的关系，试验研究表明：无荷膨胀变形主要分为快速膨胀、减速膨胀和最终稳定3 个阶段；在初始干密度一定时，风化砂改性土的无荷膨胀率会随着掺砂比例的增大先迅速降低然后缓慢降低，风化砂改性土的无荷膨胀率对较大的掺砂量不敏感；在相同的掺砂比例下，风化砂改性土的无荷膨胀率随着初始干密度的增大会迅速增大，它们之间有很好的线性相关性，膨胀土在进行路基填筑时，控制初始干密度有助于减小其膨胀变形，保证路基填土的稳定性。

Through the indoor free load swelling rate test，Yichang City，a section of a highway reconstruction project of expansive soil were studied. Key analysis free load swelling rate of a non-load time，the proportion of mixed sand，the relationship between the initial dry density， experimental studies have shown that：Free load swelling rate is mainly divided into rapid expansion，slow expansion and eventually stabilize in three stages；during the initial dry density is constant，weathered sand soil free load swelling rate will increase the proportion of sand mixed with the rapid decrease slowly after the first lower，weathered sand soil modified free load swelling rate is not sensitive to the amount of sand mixed；in the same mixed sand ratio， weathered sand soil free load swelling rate increases with increasing initial dry density increases rapidly between them have a good linear correlation，expansive soil subgrade construction in progress when control of the initial dry density，to help reduce its swelling deformation，ensuring the stability of embankment.