为求解基坑工程围护结构出现渗漏而采用局部冻结止水的温度场分布,以基坑阳角处3 管冻结封水为背景,考虑地连墙绝热边界的影响,基于热势叠加理论和镜像法,推导获得稳态温度场解析解,并通过不同特征截面上解析与数值结果的对比,验证解析解的准确性和适用性.研究表明:1)稳态条件下各特征截面的温度误差在 0.3℃以内,解析解具有足够的精确性;2)随着冻结天数的增加,冻结模型由非稳态逐渐向准稳态转变,温度误差不断减小,由第 10 天的17.1℃降低到第100 天的0.3℃,解析解随冻结时间延长而逐渐适用和准确;3)铺设保温材料的地连墙限制了冷量的耗散,有利于基坑阳角与冻结管轴面之间土体的降温,而冻结管轴面对称位置的冻土温度明显更高(最大温差达 17℃),成为冻结薄弱区域;4)在基坑局部渗漏水冻结修复时,考虑绝热边界积极效果的同时也应关注冻结薄弱区域的存在,以优化冻结管与绝热边界的位置关系.
An analytical solution for the steady-state temperature field of three-pipe freezing and water sealing at the corner of a foundation pit is derived to investigate the temperature field distribution of local freezing and water sealing for leakage in the retaining structure of foundation pit engineering.The derivation is based on thermal potential superposition theory and the mirror image method,considering the influence of the adiabatic boundary of the diaphragm wall.The analytical and numerical results of different characteristic sections are compared to validate the accuracy and applicability of the analytical solution.The findings are as follows:(1)The temperature error of each characteristic section under steady-state conditions is within 0.3℃,indicating that the analytical solution is accurate.(2)The freezing model gradually becomes stable with increasing freezing time,and the temperature error decreases from 17.1℃ on the 10th day to 0.3℃ on the 100th day of freezing.The analytical solution shows applicability and accuracy with freezing time.(3)The diaphragm wall with thermal insulation material limits the dissipation of cold energy,which is conducive to the cooling of soil between the positive corner of the foundation pit and the axial plane of the freezing pipes.The frozen soil temperature at the symmetrical position of the axial plane of the freezing pipes is significantly higher(the maximum temperature difference is 17℃),indicating a bad freezing effect.(4)The adiabatic boundary should be considered to improve the positional relationship with freezing pipes.