盾构尾刷冻结法更换的温度场数值分析

 对上海长江隧道长距离盾构掘进中盾尾刷更换预案的冻结法施工温度场进行三维有限元数值分析，对此特殊冻结法的可行性和可靠性进行论证。根据冻结法盾尾刷更换方案，依照实际工程的地质条件、盾构和管片结构以及密封油脂等相关介质的热物理性质，考虑盾尾刷更换的具体工艺，采用ANSYS软件对盾尾刷更换施工过程进行温度场数值计算，在此基础上对冻土帷幕的发展、厚度变化和封闭性进行分析。结果表明，开始冻结后在盾尾可以很快形成封闭的环形冻土帷幕并稳定发展，拆卸临时管片进行盾尾刷更换过程中，冻土帷幕略有弱化但很快转入继续增长并进入稳定的安全状态，论证设计的冻结法盾尾刷更换方法的可行性和可靠性。

NUMERICAL ANALYSIS OF TEMPERATURE FIELD DURING REPLACEMENT OF SHIELD TAIL BRUSH BY FREEZING METHOD

A 3D finite element analysis of the temperature field by freezing method adopted in the preparatory plan for the shield tail brush replacement after long-distance excavation in the Shanghai Yangtze River Tunnel is given to show the feasibility and reliability of the special program of the freezing method. According to the shield tail brush replacement plan by freezing method,in conformity to the geological conditions,structure of the shield machine and the segments and the thermo-dynamical properties of the sealant-grease and other related media,with the replacement technology taken into account,the temperature field during the tail brush replacement process is computed by the software ANSYS for analysis of the growth ratio,the thickness development and the watertightness of the frozen soil zone. The results demonstrate that the frozen soil ring can come into a closure state in a short time after the freezing process starts and then develop steadily. It is also shown that the frozen body will be weakened when the segments of the temporary ring are removed but it can soon go on growing and turn into a safe state. The conclusion is that the tail brush replacement plan by freezing method is feasible and reliable.