单次降温条件下硫酸盐渍土盐冻胀试验研究

为研究单次降温条件下不同压实度、含水率、含盐量对宁夏地区硫酸盐渍土盐冻胀的影响,进行了室内配置试样试验。结果表明:在单次降温条件下,该地区硫酸盐渍土的起胀温度随含盐量增加而增大。随着温度变化,盐冻胀过程表现为4个阶段:35 ℃~ 5 ℃之间属于纯盐胀阶段,5 ℃~-5 ℃之间属于调整阶段,-5 ℃~-10 ℃之间属于盐冻胀阶段,-10 ℃~-25 ℃之间属于稳定阶段。当压实度较低、且含盐量在2%以内时,盐冻胀率随含盐量增加有所增大;当含盐量超过2%后,盐冻胀率随含盐量增加呈先增大后减小发展趋势,并在含盐量5%时达到峰值。当压实度为100%时,盐冻胀率随含盐量增加而增大。当含盐量较小时,达到最优含水率时盐冻胀率较大;而随含盐量逐渐增大,盐冻胀率随含水率增加呈先减小后增大变化趋势。总体来看,压实度越高、含盐量越大、越接近土体最优含水量时,盐冻胀率也越大。该研究可为硫酸盐渍土地区的工程建设提供参考。

Experimental Study on Salt Expansion and Frost Heaving Characteristics of Sulfate Saline Soil under the Condition of Unilateral Cooling

Saline soil is a regional special soil, the salt expansion properties have certain influence on infrastructure construction. In order to study the influence of different compaction degree, water content and salt content on salt and frost heaving of sulphate saline soil in Ningxia area under unilateral cooling condition, an indoor configuration sample test was conducted. The results show that: Under the condition of unilateral cooling, the swelling temperature of sulfate saline soil increases with the increase of salt content in this area. With the change of temperature, the process of salt and frost expansion appears as four stages: 35 ℃~ 5 ℃ belongs to the pure salt expansion stage, 5 ℃~-5 ℃ belongs to the adjustment stage, -5 ℃~-10 ℃ belongs to the salt and frost heaving stage, -10 ℃~-25 ℃ belongs to the stable stage. When the compaction degree is lower and the salt content is less than 2%, the salt and frost expansion rate increases slowly with the increase of salt content. When the salt content is more than 2%, the salt and frost expansion rate increases first and then decreases with the increase of salt content and reaches the peak on the salinity of 5%. While the compaction degree reaches 100%, The salt and frost expansion rate will enlarge with the increase of salt content. When the salt content is small, the salt expansion rate will be greater under the condition of reaching the optimum moisture content. With the increase of salt content, the salt and frost expansion rate will show a tendency as decreasing first and then increasing with the increase of water content. In general, the higher the degree of compaction, the greater the salt content, the closer to the optimal soil moisture content, the greater the frost expansion rate will be. This study can provide references for the engineering construction in the sulphate saline soil area.