地铁隧道半断面水平冻结施工的水热力耦合特性研究

地层冻结是一个水、热、力三场耦合问题,基于考虑相变的水热力耦合理论,分析地层温度场、水分场随时间的变化规律,对比冻结前后隧道开挖的位移场分布特点。研究表明:随着冻结时间的增加,冻结管周边土体的温度将逐渐降低并发生冻结,出现冻结区域扩大、交圈、冻结帷幕增厚等变化过程;冻结帷幕内的冻土存在未冻结水,随着冻结时间的增加,大多数位置的未冻结水体积含量出现先增大后减小的变化趋势;建议在冻结帷幕两侧下方追加冻结管以保证实际的冻结帷幕达到设计范围,并对冻结管距开挖轮廓线的距离进行差异化设定。

Study on Moisture-Heat-Stress Coupling Characteristics in Metro Tunnel Construction with Half-Section Horizontal Freezing

Ground freezing is a issue in relation to the coupling among the moisture field,temperature field and the stress field. Based on moisture-heat-stress coupling theory which is in consideration of phase variation,the variations of both the temperature field and the moisture field with the time passing were analyzed,and the distribution characteristics of displacement field in tunnel excavation were contrasted between unfrozen soil and frozen soil. The result shows: with the increasing of freezing time,the temperature of the soil surrounding the freezing pipe will gradually lower and the freezing phenomenon will occurs. Subsequently,the following variation processes will happen: the expansion of the freezing region,the enclosing of frozen soil,and the thickening of frozen soil curtain. Moreover,the unfrozen water exists within the frozen soil curtain,but with the freezing time increasing,the volume content of unfrozen water increases at first and then decreases at most positions. It is suggested that the amount of freezing pipes in both sides below the frozen soil curtain should be increased in order to ensure that the actual frozen soil curtain can reach to the design rang,and the distances from the freezing pipes to the excavation contour line should be designed differently.