The type and number of threads on the bolt, the bolt material and the torque applied.
With suitable rolling method, a high strength (500 600 MPa), high elongation bolt material has been developed.
Based on the findings above, a series of bolt materials with a high yielding strength of 500 830 MPa and a high extension ratio, and cable bolt material with a 1 × 19 structure, large tonnage and high extension ratio are developed.
Particular emphasis is put towards relaxation caused by the flange and bolt material creep.
The bolt is designed to fully use both the strength and the deformation capacity of the bolt material along the entire length.
Static pull tests and dynamic drop tests show that the bolt length elongates by 14 20% at a load level equal to the strength of the bolt material, thereby absorbing a large amount of energy.
Data for case analysis are collected from original tower design reports, the tower design code, construction records and documents, historical wind-speed data, structural tower analysis, and intact and fractured bolt material tests.
It was further demonstrated that the strength of blasting, the distance between the rock bolt and the blasting point and the Young's modulus of the rock mass and the bolt material are the most important factors having significant influences on the mechanical behaviour of GFRP bolts.
Also, decide on the minimum wall thickness, number of bolts, allowable normal stress of the stainless material, and allowable normal stress of the bolt material.
These bolting materials have been widely used in Chinese coal mines.
