Metro bolts are generally lined ring-shaped. A bow bolt, on the other hand, is a precast lining of concrete (which is usually made of several pieces). It is mainly used in the construction of large sewage pipes and subways. In the process of tunnel excavation, the main function of the bow screw is to waterproof and support.
Steam curing is about heating the concrete externally to accelerate the formation of the internal structure of the cement and the hydration reaction, so that the hardening rate of the concrete is accelerated. The main purpose is to shorten the turnaround cycle of the template and increase the output. Under normal circumstances, the maintenance method of the bow screw is mainly atmospheric steam solid method, and the four main stages of maintenance are: (1), pre-curing (Y); (2) Heating(s); (3) Cooling (J) and constant temperature (H)
The connection method of the bow screw inside the lining ring and the screw outside the lining ring can be divided into two types: flexible connection and rigid connection, wherein the two adjacent bow screws in the flexible connection can have slight compression and rotation, so that the lining ring can be deformed according to the distribution of internal forces to change the stress state of the lining. In the rigid connection, the number of rows of connecting bolts can be increased, and the rigidity of the connection position is the same as the rigidity of the bow bolt itself. Nowadays, flexible connection methods are more commonly used.
In the construction of subway tunnels, we generally use subway bolts for construction. The lining is cylindrical, connected with bow screws in reinforced concrete. This design form needs to be grouted at the reserved position of the connecting screw and the subway bolt, and the main function is to prevent seepage and waterproof.