One, from the perspective of the entire supporting system, the main functions of the pipe shed are as follows:

1. The pipe shed primarily serves to reinforce the rock mass (host rock). Materials such as cement, water glass, or foam polyurethane are injected into the host rock through holes in the steel pipe, improving the condition of the host rock and ensuring the stability of the working face. There are two corresponding analytical methods. One method is to approximate the reinforcement effect of the pipe shed by improving the mechanical parameters of the rock mass; the other involves simulating with solid elements or shell elements.

2. The pipe shed plays a supporting role. The corresponding analysis model is the load-bearing beam model, which is the main calculation model in current pipe shed analysis. Depending on whether the influence of the rock mass is considered, there are two cases. One is not considering the influence of the rock mass, treating the pipe shed as a beam fixed at both ends. For large-diameter pipe sheds (commonly used in Europe and Japan, represented by the Japanese pipe curtain construction method), this type of analysis model is often adopted. Another method is to consider the supporting role of the rock mass below the pipe shed, treating the pipe shed as embedded in the rock layer, but the understanding of its role is still limited to the pipe shed as a load-bearing component. The focus is on determining the upper load of the pipe shed and analyzing its load-bearing characteristics.

3. The pipe shed serves to disperse and transfer the loads associated with excavation and unloading. For conventional span tunnels with small-diameter pipe sheds (diameter below 159mm), the pipe shed generally does not bear the loads during excavation and primarily functions to transmit and regulate the loads released during excavation. Whether the pipe shed bears or transmits loads mainly depends on the relative stiffness ratio between the pipe shed and the supporting structure.