粉质黏土水泥土冻胀融沉特性研究

为研究水泥土冻胀融沉特性，对南京地区典型粉质黏土进行了不同条件下的冻胀融沉试验。试验控制因素包括水泥掺入比、含水率、龄期、冷端温度和荷载等，各控制因素在包含基准数值的区间内选取代表性条件进行单一变量试验。试验采用自制冻胀融沉仪进行，冻胀融沉仪下部为制冷块，上部设置补水装置，模拟真实土体冻结时水分迁移过程。结果表明：粉质黏土水泥土冻胀率随水泥掺入比增大、龄期增加呈指数规律减小，随含水率增大、冷端温度升高和荷载减小呈线性增大；融沉系数随水泥掺入比变化规律与冻胀率类似，同一条件下融沉系数均大于冻胀率；水泥土完成融沉的时间随解冻温度升高而减少，但最终融沉系数相同；冻胀融沉存在合理水泥掺入比，粉质黏土的合理水泥掺入比为10%，此时冻胀率为1.56%，融沉系数为2.15%。据此提出，冻结法施工时，预先在土体中按合理水泥掺入比掺入水泥，既可有效抑制土体冻胀融沉，又可提高施工效率。

Experimental study on the frost heave and thaw settlement properties of cement-improved silty clay

In order to study the frost heave and thaw settlement properties， experimental researches were carried out with silty clay in Nanjing region. Test control factors include the mixing ratio of cement， moisture content， age， cold junction temperature and load. Each control factor selects representative conditions within the interval containing the benchmark value to conduct a single variable test. The test was carried out with frost heave and thaw settlement instrument. The lower part of the instrument was equipped with a refrigeration block， and the upper part was equipped with a water supplement， to simulate water migration process when real soil is frozen. Frost heave of cement-improved silty clay declines exponentially with mixing ratio of cement and age increasing， enhances linearly with moisture content， cold junction temperature rising and load reducing. The mixing ratio of cement also influences thaw settlement of cement-improved silty clay， which is in line with the law in frost heave. Thaw-settlement coefficient is higher than frost heaving ratio in same situation. The time of completing thaw settlement declines with thawing temperature， while thawing temperature has no impact on final thaw-settlement coefficient. The reasonable mixing ratio of silty clay in Nanjing is 10%. Frost heaving ratio is 1.56% and thaw-settlement coefficient is 2.15% in reasonable mixing ratio. In conclusion， mixing cement into soil beforehand can control frost heave and thaw settlement effectively in artificial freezing construction and enhance productivity.