地铁联络通道冻结施工的热流固(THM)耦合分析

THM Coupling Analysis of Connected Aisle in Metro Construction by Artificial Freezing Method

随着城市地铁规模的不断发展,冻结法在地铁联络通道施工中得到了广泛应用.为了得到合适的地层冻结工艺参数和指标,了解开挖隧道对地层稳定性的影响,保证工程的安全性,基于考虑相变及冻胀的热-流-固(THM)耦合理论,采用COMSOL有限元分析软件模拟某地铁联络通道水平人工冻结及开挖施工过程.分析了冻结过程中地层温度场、渗流场及位移场的变化规律,研究了开挖后地层位移场的分布规律.结果表明:由于水渗流作用,温度场和位移场的分布不再关于y轴对称;在人工冻结过程中,地表处冻胀位移的最大值出现在y轴以右,冻胀量变化表现为先线性增长,而后趋于稳定.总体上,实施人工冻结可以很好地增加周围土体的强度及稳定性,对止水和抑制地层变形具有良好的效果.

As the development of city metro, artificial freezing method is widely used in connected aisle construction. For ensuring the safety of projects, to get appropriate freezing parameters and guidelines and to find out the excavation influence on stability of stratums are very important. Considered phase change and frost heave deformation, based on the thermal-hydrological-mechanical （THM） coupling theories, the freezing and excavation processes of a certain connected aisle in metro was simulated by COMSOL finite-element analysis software. The transformations of seepage field, temperature field and displacement field during freezing period and the deformation of stratums after excavation were analyzed. It is found that owing to the seepage of water, the distribution of temperature field and seepage field are no longer symmetrical about y-axis, and the thickness of the frozen wall in the upstream is less than that in the downstream. During the process of freezing, the transformation of frost heave deformation shows linear increase firstly, and then becoming steady. The maximum frost heave deformation of surface appears at the right side of y-axis. Overall, artificial freezing of stratum is helpful for increasing the intensity and stability of solid, and also possesses a well effect on water isolation and deformation controlling.