Abstract: In order to reduce the expansion rate of phyllite and the shrinkage rate of red clay, a physical-chemical combined method for improving phyllite was proposed. 24 different combination improvement schemes were designed with a mass mixing ratio of 0, 20%, 40%, 60%, 80%, and 100% for red clay, and a mass mixing ratio of 0, 3%, 5%, and 8% for lime. The expansion and shrinkage characteristics of the composite modified soil were analyzed through the test on the expansion and shrinkage of the fully weathered phyllite composite modified soil, and the mechanism of the dilatation and shrinkage characteristics of the red clay and lime composite modified phyllite was explained from the microscopic perspective. The test results show that the evolution law of the free expansion rate is similar to that of the no-load expansion rate. The expansion rate decreases with the increase of the red clay blending ratio. With the increase of the lime content, the expansion rate firstly decreases rapidly and then tends to be stable, and the optimal lime dosage is 3%. After adding lime, the expansion force firstly decreases and then increases with the red clay blending ratio and reaches the lowest when the red clay blending ratio is 60%. When the lime content is greater than 3%, the improvement effect is not significantly improved compared to the lime content of 3%. The linear shrinkage rate of soil samples decreases with the decrease of the red clay blending ratio and the increase of the lime content, and the decrease is relatively small when the lime content is greater than 3%. The comprehensive shrinkage test results show that the effect of reducing the shrinkage deformation of red clay with phyllite soil is better than that with lime. With each lime content, the shrinkage limits all firstly decrease and then increase with the increase of the red clay blending ratio and reach the lowest when the red clay blending ratio is about 40%. Based on the results of the expansion and shrinkage test, it is suggested that the optimal dosage is 40%~60% for red clay and 3% for lime. At this time, the free expansion rate is reduced by 24%~26%, and the no-load expansion rate is reduced by 25.9%~27.0%; the expansion force is reduced by 639~593 kPa, and the linear shrinkage rate is reduced by 0.7%~0.8%.

Key words: highway engineering; expansion and shrinkage characteristics; red clay; phyllite soils; mutual improvement

摘要： 为降低千枚岩土的膨胀率和红黏土的收缩率，笔者提出了一种物理-化学联合改良千枚岩土的方法，设计红黏土质量掺和比为0、20%、40%、60%、80%和100%，石灰质量掺量为0、3%、5%和8%共计24种不同组合改良方案。通过全风化千枚岩复合改良土胀缩性试验，分析了复合改良土的胀缩特性，并从微观角度解释了红黏土、石灰复合改良千枚岩土胀缩特性的机理。试验发现自由膨胀率演化规律与无荷膨胀率相似，膨胀率随红黏土掺和比的增加而降低，随石灰掺量增加，膨胀率先快速下降后趋于稳定，得出石灰优化掺量为3%。掺入石灰后的膨胀力随红黏土掺和比先降低后增大，红黏土掺和比60%时达到最低。当石灰掺量＞3%时，改良效果较石灰掺量3%时提升不显著。土样线缩率随红黏土掺和比的降低、石灰掺量的增加而减小，且石灰掺量＞3%时降幅较小。综合收缩试验结果可知：千枚岩土降低红黏土收缩变形效果优于石灰；各石灰掺量下，缩限皆随红黏土掺和比的增加先降低后升高，在红黏土掺和比约40%时达到最低；综合胀缩试验结果，建议优化掺量为红黏土掺和比40%~60%、石灰掺量3%，此时自由膨胀率降低24%~26%，无荷膨胀率降低25.9%~27.0%，膨胀力降低639~593 kPa，线缩率降低0.7%~0.8%。

关键词: 道路工程；胀缩特性；红黏土；千枚岩土；相互改良