For a long time,due to ordinary mortar anchor bolt has low cost advantage,so it is widely used in tunnel and slope geotechnical anchoring domains,but with the development of geotechnical anchoring technique and the application of hollow anchor bar, the advantage of hollow anchor bar in the field of geotechnical gradually occurs and take place of mortar anchor bolt in many fields,what are the advantages to make hollow anchor bar more and more widely used in the field of geotechnical anchorage?So we can make a brief analysis from the following points.

1, the cost of use.

In recent years with the continuous development of hollow grouting technique and the promotion, the application of hollow anchor bar range continuously extend, the production of hollow anchor bar and its accessories increased dramatically, which make the raw materials of hollow anchor bar processing and the anchor bolt rolling equipment production scale, hollow anchor bar and its accessories also gradually realize automation of production, which significantly reduces the cost of hollow anchor bar, at the same time the anchor ability of hollow anchor bar is more than mortar anchor, further by reducing hollow anchor bar using density to reduce the project cost , therefore, the cost of using of hollow anchor bar in engineering compared with the using of mortar anchor was similar.

2.Durable degree

Hollow anchor bar grouting by rod hole in the body from the inside to outside，at the same time, the outside of hollow anchor bar which plus plate and plug，which can effectively prevent slurry spillover, when necessary, also can undertake pressure grouting, make grout diffusion to the surrounding rock fracture, so the rod body around hollow anchor rod can form a thick enough and uniform coating, significantly improve the durability of the rod body;And ordinary mortar anchor  is often using technology of grouting first ,and then insert bar, this process is difficult to guarantee grouting full degree, therefore it is often hard to avoid phenomenon of the steel rod body naked , if the naked steel contact with the ground water will lead to bare steel reinforcement corrosion,thus reduce the durability of the hollow anchor bar.

3, geological environment adaptability.

Hollow anchor bar can be used to drill with the method of combined drill pipe and hollow anchor body in one way, in soft crushing, which is able to used in weak,difficult hole formation, however ordinary mortar need to drilling in advance,therefore, in the face of the weak and broken rock mass construction, pulling out the drill pipe often leads to the phenomenon of hole collapse response capacity.

4, using expansion shell anchor bolt or prestressed anchor bolt, through the way of tightening nut or tensioning device can pass the tensile load to voluntarily gneiss,which can improve the weak structural plane or the potential sliding surface of shear strength.And generally ordinary mortar anchor has no plate at the moment and are unable to provide prestressed.

By the above content, you can see that compared using hollow anchor bar with ordinary mortar anchor can greatly improve the quality of engineering, at the same time the actual construction cost is not too big increase.