For a long time, ordinary mortar bolts have been widely used in geotechnical anchoring fields such as tunnels and slopes due to their low cost. The advantages of the field are gradually reflected and gradually replace the mortar bolt in many fields, so what are the advantages that make the hollow rock anchor bolt more and more widely used in the field of geotechnical anchoring? A brief analysis can be made from the following points.
Cost of Use
In recent years, with the continuous development and promotion of hollow grouting technology, the application range of hollow bolts has continued to expand, and the output of hollow bolts and their accessories has increased significantly, making the processing of hollow bolt raw materials and the production of bolt rolling equipment on a large scale. Hollow bolts and their accessories are gradually being produced automatically, which greatly reduces the cost of hollow bolts. At the same time, the anchoring capacity of hollow rock anchor bolts is much larger than that of mortar bolts. It can be adopted to reduce the use density of bolts to further reduce engineering costs. Therefore, the cost of using a hollow bolt in a project is comparable to that of using a mortar bolt.
Durability
A hollow rock anchor bolt is grouted from the inside to the outside through the inner hole of the rod. At the same time, the outer end of the anchor hole is provided with a grouting plug and a backing plate, which can effectively prevent the slurry from overflowing. If necessary, pressure grouting can be carried out to make the slurry diffuse to the rod body. Due to the cracks in the surrounding rock and soil, a sufficiently thick and uniform protective layer can be formed around the hollow bolt, which greatly improves the durability of the rod body; while the ordinary mortar bolt often adopts the process of grouting first and then inserting steel bars, which is difficult to ensure full grouting. Therefore, it is often difficult to avoid the exposed steel bar of the rod body. If the exposed steel bar is in contact with groundwater, it will cause corrosion of the steel bar and reduce the durability of the anchor.
Adaptability to the Geological Environment
The hollow rock anchor bolt can be drilled by combining the drill pipe and the hollow bolt body, so it can be used in the stratum that is weak and broken and difficult to form holes, while the ordinary mortar bolt generally needs to be drilled in advance, so in the face of weak and broken rock mass construction, the ability to deal with the phenomenon of hole collapse often occurs when the drill pipe is pulled out is poor.
Provide Prestress
The use of hollow rock anchor bolts with expanded shells or prestressed self-propelled hollow rock anchor bolts can actively transmit the tensile load to the rock and soil mass by tightening the nuts or tensioning devices, which can improve the weak structural surface or potential slippage. Shear strength of the moving surface. The ordinary mortar bolt generally has no backing plate, so it cannot provide prestress.
It can be seen from the above content that the use of hollow rock anchor bolts can greatly improve the project quality compared with ordinary mortar bolts, and the actual construction cost does not increase much.