渠道保温防冻胀中冻土层等效导热系数的计算

针对渠道保温防冻胀设计中计算保温板厚度时关键参数冻土层等效导热系数采用经验法确定、计算误差大等问题,建立了北方寒冷地区粉质黏土的基于分形理论的冻土层等效导热系数λ*的计算公式,利用蛤蟆通灌区试验资料拟合得到系数C的计算公式,并通过内蒙古河套灌区、新疆冲乎尔灌区和黑龙江蛤蟆通灌区渠道保温防冻胀试验资料对建立的冻土层等效导热系数公式进行了验证。结果表明,计算得到的聚苯板厚度与试验观测的最佳厚度基本一致,最大相对误差仅为7.0%,说明其计算精度较高。利用该公式计算得出了粉土及粉质黏土常用冻土层等效导热系数,对于地下水埋深较浅、渠基土冻结期间存在水分迁移、冻胀较为严重的地区,在实际工程应用中可根据设计渠道情况进行选用。

Calculating the Effective Thermal Conductivity Coefficient of the Frozen Layerin Thermal-conservative and Freezing-resistant Cannel

Empirical methods commonly used for calculating the effective thermal conductivity coefficient of the frozen layer in thermal-conservative and freezing-resistant cannels could give rise to considerable errors. To over-come this problem, we proposed a fractal-based model in this paper to calculate effective thermal conductivity co-efficient of silty clay in permafrost in the cold region of northern China. We calculated the coefficient C using da-ta obtained from Ha Matong Irrigation District and then applied and tested the model against data obtained from-Hetao Irrigation District in Inner Mongolia, Chong Huer Irrigation District in Sinkiang, and Ha Matong Irrigation District in Heilongjiang. The results showed that the calculated thickness of polyphenyl plate was almost the same as the optimal thickness with an error of just 7.0%, proving the accuracy of the model. We also calculated the effective thermal conductivity coefficient of silt and silty clay in permafrost. The model can be used in re-gions where groundwater table is shallow and there is soil water movement when soils are freezing with pro-longed frost heaves.