引洮7~#隧洞TBM卡机脱困冻结施工热固耦合分析

基于考虑相变的热固耦合理论,以引洮7#隧洞TBM卡机脱困施工为背景,运用大型有限元分析软件ANSYS14.0对该TBM脱困过程的冻结施工进行模拟,研究了先竖直冻结、后水平冻结条件下温度场的形成过程,以及在温度应力和重力共同作用下实施脱困后关键点的位移变化。结合现场监测数据,分析了冻土帷幕形成过程中关键点处温度变化规律。结果表明:冻结锋面在水平冻结进行约35 d首次相交,再经过30 d积极冻结后,冻结帷幕达到2.7 m的设计厚度。在冷媒温度保持-21℃左右的条件下,进行65 d的维护冻结后即可进行脱困作业。开挖后55 d,洞身断面顶拱、底拱、侧拱均发生不同程度的变形,变形量在10-4m数量级,属极小变形,说明冻结施工有效地抑制了地层变形,但要使冻结强度达到设计标准,必须严格控制冻结时间和冷媒温度。本工程的工程实践为类似工程提供借鉴。

Thermo-solid coupling analysis on freezing construction for de-blocking TBM blocked in No.7 Tunnel of Taohe River Water Diversion Project

Based on the thermo-solid coupling theory under consideration of phase transition and taking the de-blocking construction of the TBM that blocked in the No.7 Tunnel of Taohe River Water Diversion Project as the background，the process of the freezing construction for the de-blocking construction is simulated with the large-scale finite element software——ANSYS14.0，and then the forming process of the temperature field under the condition of vertical freezing at first and then horizontal freezing as well as the displacement changes of the key points after the implementation of the de-blocking construction under the common effect of both the temperature stress and the gravity are studied. In accordance with the in situ monitoring data，the temperature changing laws of the key points during the forming process of the freezing soil curtain are analyzed as well. The result shows that the frozen fronts are initially intersected after implementing the horizontal freezing for about 35 d and the frozen curtain reaches to the design thickness of 2.7 m after the active freezing for another 30 d. After the maintenance freezing of 65 d under the condition of keeping the temperature of the polycold at about -21 ℃，the de-blocking construction can be carried out. After 55 d of the excavation，the deformations of various degrees occur at all the crown，invert and side arch of the tunnel cross-section with the deformation amount at 10-4m which belongs to the minimal deformation，thus it is indicated that the ground deformation is effectively restricted by the freezing construction. However，the freezing time and the temperature of the polycold must be strictly controlled for making the frozen strength reach the design standards concerned.