Study On Theory And Test Of Tunnel Construction By Artificial Horizontal Freezing Method

As the faster pace of the urbanization it is necessary to exploit the space underground. Freezing method of artificial layer, with several advantages, becomes the optimum for the underground project. On the other hand there are many factors affecting the project, most of which locate in the urban areas. All of these increase the hazards.This article first makes a theoretical analysis on the temperature field in frozen wall and the characteristics of frost heave and thawing settlement, then deduces the forming law of frozen wall and discusses the effect of frost heave and thaw collapse on the frozen wall, underground tunnel line and ground-distortion in the horizontal freezing process construction. Secondly we derive the similarity criterion of freezing method in tunnel construction by using the fundamental of similarity theorem and make large-scale physical mode testing. Finally we build a calculation mode for tunnel excavation process and use numerical analyzes software to study.According to the testing mode (2.0m frozen wall) in this article, the degrade gradient in the temperature field of froze wall is larger (normally 1.6℃/h) above 0 ℃, and mild below 0 ℃, (normally 0.3 ℃/h~0.5 ℃/h) . At the same time in the process of freezing there is some kind of frost heave in the soil. The largest distance of frost heave on the surface of the soil can reach to 17mm and 22.4mm in the frozen wall. In the unfrozen process, the thaw collapse motion increase linearly. The largest distance of thaw collapse can reach to 56.9 mm in the frozen wall and 39.1mm on the surface of the soil. The result of numerical calculation coincides the physical model testing. After theoretical analysis, model testing and numerical calculation, we verify the flexibility of horizontal freezing method and have an in-depth look at the factors affecting the method. This article is a good example to the design and construction of horizontal freezing method.