盾构隧道端头垂直冻结板冻结加固温度场数值分析

Numerical Analysis on the Temperature Field of Freezing Reinforcement with Vertical Freezing Plate at the End of Shield Tunnel

为探究盾构隧道端头垂直冻结板的冻结加固效果、优化冻结板冻结加固方案,首先介绍了盾构隧道端头垂直冻结板冻结加固结构,然后运用有限元软件进行分析,数值建模分析该垂直冻结板冻结加固温度场的发展规律,最后结果表明:冻结板板厚对于最终冻结效果影响较小,板厚最佳为200 mm;增加冻结板与地连墙距离能显著增加最终有效冻结厚度,但冻结距离过大会导致靠近地连墙部分土体冻结效果变差,最佳距离为800 mm;路径4和路径5分别位于冻结板左右两边,与冻结板距离均为0.8 m,但2条路径最终冻结效果和降温历程均有较大区别,其原因在于,路径5为土体与地连墙接触面上路径,在温度场模拟时设置土体表面为绝热,故低温会在路径5所在表面迅速积累不会扩散;路径4附近土体并不绝热,所以造成了以上差别.

In our report, in order to explore the effects of freezing and strengthening of the vertical freezing plate at the end of shield tunnel and optimize the scheme of freezing and strengthening of the plate, firstly, the freezing strengthening structure of the vertical freezing plate at the end of shield tunnel was introduced;secondly, USES finite element software was used to analyze the development law of the temperature field of the freezing strengthening of the vertical freezing plate by numerical modeling. The results showed that the thickness of the freezing plate has little influence on the final freezing effects, and the best thickness is 200 mm.The increasing of the distance between the freezing plate and the geodesy can significantly increase the final effective freezing thickness, however, too large a freezing distance will result in poor freezing effects of the soil near the geodesy, the optimal distance is 800 mm. Path 4 and path 5 is located on the left side and the right side of the freezing plate, respectively, with a distance of 800 mm from the freezing plate.However, the final freezing effects and cooling process of the two paths are significantly different. The reason is that path 5 is the path on the contact surface between soil and the geodesic wall, and the soil surface is set as adiabatic during the temperature field simulation, low temperature accumulates rapidly on the surface of path 5 without diffusion, the soil around path 4 is not adiabatic.