联络通道冻结施工近隧道端土体温度场分布及管片保温措施优化

Distribution of Soil Temperature Field Close to Tunnel End and Optimization of Segment Insulation Measures in Cross-Passage Construction by Artificial Ground Freezing Method

为了研究人工冻结法施工联络通道中近隧道端土体温度场的分布规律以及管片散热对土体温度场的影响,采用现场实测和数值计算的方法,对土体温度场分布、冻结壁厚度和管片保温措施进行分析。结果表明:土体温度、冻结壁扩展厚度均随深度的增加呈指数型变化,当深度大于2.2 m时冻结壁厚度和冻土温度场基本稳定;联络通道的冻结壁沿长度方向可划分为2侧交界面段与正常冻结段;冻结管间距是影响交界面段冻结壁厚度的重要因素之一,因此辅助冻结面冻结壁是联络通道施工中的主要风险点之一;管片散热对土体影响范围与冻结时间呈对数关系,随着冻结时间的延长,影响范围将逐步扩大;为保证交界面区域的冻结效果,可在钢管片内部靠近土体一侧增设5 cm夹心保温层或改良管片壁后注浆材料2种管片保温,优化后交界面靠近管片位置冻结壁厚度可提升约24%。

In order to study the distribution of soil temperature field close to the tunnel end and the influence of segment heat dissipation on the soil temperature field in tunnel cross-passage construction by artificial ground freezing(AGF)method,the distribution of soil temperature field,the thickness of frozen wall and the measures of segment insulation were analyzed by adopting the methods of field measurement and numerical calculation.Results show that the soil temperature and the expanded thickness of frozen wall change exponentially with the increase of the depth.When the depth is greater than 2.2 m,the thickness of frozen wall and the temperature field of frozen soil are basically stable.The frozen wall of the cross-passage can be divided into 2 parts along the length direction:the interface sections on 2 sides and the normal freezing section.The spacing of freezing pipes is one of the important factors for the thickness of the frozen wall at the interface section.Therefore,the frozen wall in the auxiliary frozen surface is one of the main risk points in the construction of cross-passage.The influence range of the heat dissipation of segment on soil is logarithmic with the freezing time.With the extension of freezing time,the scope of influence will gradually expand.The freezing effect of the interface area can be ensured by adding a 5 cm sandwich insulation layer in the inner side of the steel segment near the soil mass or by improving the grouting material behind the segment wall.After optimization,the thickness of the frozen wall close to the segment in the interface section can be increased by about 24%.