水下清淤人工冻结板温度场数值分析

为研究水下清淤人工冻结板温度场的发展规律以及冻土帷幕形成的过程，通过有限元分析软件，采用单因素分析法进行数值分析，研究了水下人工冻结板在几何及物理环境变化条件下的冻结规律。结果表明:冻结板不同几何尺寸与清淤深度的相关性较弱，调整冻结板的几何尺寸仅能改变清淤面积；对清淤环境来说，土层的导热系数越大，比热容越小，原始地温越低，其降温速度越快，清淤越高效；砂土的冻结效果要明显优于黏土；相变潜热对土体降温的影响十分有限；盐水降温计划中最低温度对清淤深度有较大影响，在-50℃以前，冻土帷幕发展较快，每降低10℃冻土帷幕的发展厚度增加约0.4 m，而在-50℃以后冻土帷幕的发展较慢，每降低10℃冻土帷幕厚度的发展仅约为0.05 m。因此，在工程实际中，冻结初期通过调节盐水降温计划可以较好的实现冻结效果；建议盐水降温计划最低温度设置为-50℃，此时可以得到的有效清淤深度约1.5 m。研究结果可为今后的相关实际工程提供参考依据。 

Numerical analysis of temperature field of underwater dredging artificial frozen plate

In order to understand the development of the temperature field of artificial freeze dredging plates and the process of the formation of frozen curtains, the finite element analysis was used to perform numerical analysis using the single factor analysis method for research of the frozen process in different circumstances of geometric size of plate and physical environment of the soil under water. The results show that the correlation between the different geometric dimensions of the frozen plate and the dredging depth is weak, and the geometric dimension of the frozen plate can only change the area of dredging; for the dredging environment, the greater thermal conductivity of the soil layer, the smaller the specific heat, the smaller the specific heat, the lower the original geothermal temperature, the faster the cooling rate, and the more efficient the dredging is; sand is more efficient to be frozen than that of clay; the effect of the latent heat of phase change on the cooling of the soil is very limited; The lowest temperature has a great influence on the depth of dredging. Before -50℃, the curtain of frozen soil develops rapidly. The development thickness of frozen soil curtain increases by about 0.4 m per 10℃ reduction, and the development of frozen soil curtain after -50℃, the development of curtain thickness of permafrost is slower, only about 0.05 m for every 10℃ reduction; therefore, in the actual project, the freezing effect can be better achieved by adjusting the brine cooling plan at the initial stage of freezing. It is recommended that the minimum temperature of the brine cooling plan be set at -50℃, and the available dredging depth at this time is about 1.5 m. The results obtained can provide reference for related actual projects in the future.