Abstract: Theoretical analysis, field measurements, and other methods were used to analyze the relationship between axial stress, shear stress, and pre-load on the bolts and the distribution of the axial and shear stresses. The results show that the axial stress increases as the pre-stress increases. The axial stress shows a curve changing with the pre-stress upon moving from the bolt tail to its head, that is, the axial stress first increases and then decreases along the bolt and at the neutral point the axial stress reaches a maximum value. The maximum value of the axial stress, moves toward the bolt tail end as the pre-stress increases. The shear stress decreases between the roadway surface and the neutral point and then increases between that point and bolt end. The shear stress equals zero at the neutral point. The proper pre-load for the fully anchored bolt is not "the bigger the better". There is a reasonable range for the pre-load that should match the bolt support system strength.

Key words: pre-stressed bolt, full-length pre-stressed anchorage, bolt axial stress, bolt shear stress