Shotcrete technology is a key technology in tunnel construction. It uses jetting machinery to spray quick-setting concrete onto the surface of rocks or structures to strengthen and protect rocks or structures. Compared with dry shotcrete equipment, it has the advantages of effectively reducing rebound, reducing dust, increasing the thickness of one spray layer, improving the quality of jetting, and high production efficiency. With the continuous improvement of the production technology of wet shotcrete equipment and related materials and equipment, wet shotcrete machine will be widely used as a mature construction method.
1. Overview of Wet Shotcrete Equipment Technology
1.1 Principle and characteristics of shotcrete process
The concrete mixed with the accelerator is sprayed onto the surface of the rock or structure with a jet to strengthen and protect the rock or structure. The compacted and integral control of shotcrete is different from the vibrating compaction principle of ordinary cast concrete. The shotcrete is dense by high-speed jet, and its compactness is closely related to the jet process. The construction of shotcrete is simple, the mold removal, pouring and demoulding process are omitted, the construction progress is accelerated, and the compactness is higher than that of ordinary concrete, and the strength and impermeability are good.
1.2 The main role of shotcrete
(1) Fill the exposed joints and cracks to improve the strength and stability of the surrounding rock.
(2) Concrete is a kind of support that can be in close contact with a large area of surrounding rock.
(3) Through the adhesion and shearing force of the contact surface, the external force acting on the shotcrete is dispersed on the surrounding rock to prevent local blockage, and a bearing ring is formed near the wall surface of the tunnel to control the stress release of the surrounding rock.
(4) Filling in the concave surface of the surrounding rock to prevent stress concentration and strengthen the weak layer. The earth pressure is transmitted to the steel support and the anchor rod, and after the excavation, the wall surface is covered in time to prevent the surrounding rock from being weathered.
