In tunnel construction, concrete construction technology is the key to ensure the stability and safety of tunnel structure. Concrete construction of tunnels usually adopts the method of excavation and lining at the same time. This process involves multiple steps, from initial support to secondary lining, and each step is crucial. This article will introduce this construction process in detail to help readers understand the whole process of tunnel concrete construction more deeply.

　　Initial support: shotcrete and steel mesh fixing

　　After tunnel excavation, the first task is to carry out initial support to prevent the collapse of the tunnel wall. This process usually uses shotcrete as a temporary support. Shotcrete can harden quickly and provide immediate support for the tunnel wall. Subsequently, the construction workers will set up the steel mesh and use anchor rods to fix it to the tunnel wall to further enhance the stability of the initial support.

　　Secondary lining: Collaborative operation of steel bar trolley and casting trolley

　　After the initial support is stable, the tunnel enters the secondary lining stage. The secondary lining is part of the permanent structure of the tunnel and is crucial to the long-term stability and safety of the tunnel. This stage of construction requires the use of special trolleys, including trolleys for setting up and welding steel bars and casting trolleys.

　　1. Setting up and welding the steel bar trolley: First, use the steel bar trolley to set up the steel bar frame inside the tunnel. The steel bar frame must be built accurately to ensure the structural strength and durability of the concrete lining.

　　2. Casting trolley: After the steel bar frame is built, the casting trolley enters the operation for pouring concrete. In the concrete formwork, a casting port of about 50 mm by 50 mm will be reserved to ensure that the concrete can be evenly distributed, avoid the generation of bubbles and voids, and thus improve the density and strength of the concrete.

　　Tunnel concrete construction is a complex and precise process. From initial support to secondary lining, each step must be strictly controlled to ensure the safety and durability of the tunnel structure. By using shotcrete, steel mesh fixing, and the coordinated operation of the steel bar trolley and the casting trolley, tunnel builders can effectively respond to the challenges of geological conditions and build high-quality tunnel projects.