粉土因毛细水发育表现出较强冻胀特性，在冻土区建设中需关注其冻害问题。土中掺入石灰是一种常见的化学土质改良方法，但石灰对粉土的冻胀特性影响尚不清晰。为研究石灰改良粉土的冻胀特性和效果，进行了开敞系统下的一维冻胀试验，分析不同掺灰量下的温度场、变形场和水分场变化规律和机理。研究发现：土样随掺灰量增大，其冻结深度先增大后减小，冻胀量和补水量持续减小，而冻胀率先减小后增大，各指标呈不同变化规律，冻胀特性复杂；一定条件下提高掺灰量可减小冻结深度和冻胀量直至低于素土，土样抗冻性提高；而随着掺灰量变化，石灰改良粉土的冻胀率始终高于素土，土样抗冻性改良不显著。因此，在实际工程中，不能仅通过单一指标评价石灰改良粉土的效果，需结合冻结深度、冻胀量和冻胀率三个指标，综合评价石灰对粉土抗冻性的改良效果。

Special attention should be paid to the frost heave due to silt’s high capillary water content in permafrost engineering. The mechanism of lime improvement is not clear on frost resistance in silt areas. A series of one-dimensional frost heave tests to the frost heaving characteristics of lime-modified silt were carried out in an open system. The effects of different lime content on frost-heaving characteristics of silt were studied. The results show that the freezing depth of soil samples first increases and then decreases with the increase of ash content， the final frost-heave capacity and additional water amount decrease， and the frost-heaving ratio decreases first and then increases. The indexes exhibit different change rules， and the frost-heaving characteristics are complex. Under certain conditions， increasing the ash content can reduce the freezing depth and frost heave amount， while the frost heave rate of the lime-modified silt is always higher than that of plain soil. Therefore， it is necessary to comprehensively evaluate the improvement effect of lime on the frost resistance of silty soil by combining the three indexes of freezing depth， frost heave amount， and frost heave rate instead of a single indicator in specific projects.