Mechanical Effect of Bolt Length on Pressure-bearing Ring and Economic Benefit Analysis

For the problem of difficult support of roadway due to the large section, higher stress characteristics of soft rock roadway, we propose pressure-bearing ring support method based on concrete-filled steel tubular bracket, steel fiber reinforced concrete arch wall and bolt. Under the premise of satisfying the mechanical requirements of roadway support, according to an engineering example, we monitor and analyze the displacement of the pressure-bearing ring of different length bolts and the economic performance of the bolts is evaluated. The results showed that the max convergence of two-side of the roadway was 76.3 mm and the max convergence between the roof and floor was about 94.7 mm. The longer of the bolt is, the smaller of accumulative deformation of surrounding rock is, the better of supporting effect is. When roadway support reaches to 100 m, the bolt of 1.8 m is saving cost more than 40 thousands yuan than the bolt of 2.7 m. Therefore, it is of good economic benefit to select the bolt with suitable length.