Study On Impact Of Anchorage Length On Anchorage Effect

Resin bolt has been widely applied in the roadway support. As one of the crucial factors affecting anchorage, anchorage length directly decides the bonding effect of bolt anchorage and its supporting effect. Therefore, it is significant in both academia and industry to study the relation between appropriate anchorage length and support effect.Using pull test experiment, basing on the analysis of failure modes of bolt and anchorage, we study both round steel with different length and thread steel. Using MZ-II type bolt assembly device and LW-1000 type horizontal tensile testing machine, we test the effects with bolt of different length and types and anchorage of different length with steel tube after inside coarsening treatment as anchorage base. The tendency of tension, distribution of axial forces and shears stress in anchorage segment is obtained: axial forces and shear stress in anchor sector follow negative exponential distribution. In order to study the relation between bolt anchorage length and the anchorage strength, we obtain rock samples of different strength through physical experiments and use ZB4-500 type pull machine and YCQ-60B-type jack to load. Experiments show that for hard rock, the distribution of shear stress and axial forces in anchorage segment is narrow, and stress concentrates in the short range of anchorage ends. Additionally, the peak shear stress and peak axial force of hard rock are larger, compared with the peaks of soft rock. When the rock is soft, shear and axial force distribute wildly along the direction of the anchorage and change slowly. What’s more, real bolt support in mine is simulated with MZ-II type bolt assembly device in our work. Through the analysis of the intersection in anchorage segment, anchorage ratios in different anchorage lengths are obtained. The results show that long anchorage not only increases the support cost, but also weakens the anchorage effect. Industrial tests show that the proposed support scheme in our work has yielded technical and economic benefits.