Analysis of bearing distribution characteristics of pre-stressed end anchor after full anchorage

The anchorage mode in roadway bolt support design has a very important influence on characteristics of bolt bearing capacity.In this paper, the distribution characteristics of axial force and stress distribution of anchor under fully anchor and end anchor are compared by means of theoretical analysis and field measurement.The results show that the distribution characteristics of bolt bearing capacity are closely related to anchorage conditions, prestress, bolt diameter and surrounding rock strength.The axial force of anchor rod decreases in one direction along the anchorage section, and the shear stress of anchor rod increases first and then decreases along the anchorage section, which is mainly distributed within 400 mm of the anchorage section.Under the influence of strata separation and dislocation, the axial force is the dominant factor restricting the failure of surrounding rock, and the shear neutral point shows a trend of gradual transfer to the outside.Compared with end anchorage, the anchor after fully anchorage has higher sensitivity to surrounding rock deformation and failure, the stress bearing range is concentrated in the off-layer failure area, the stress peak value is significantly reduced, and the stress distribution is more uniform and gentle.From the research results, it can be seen that the fully anchorage can significantly improve the overall strength and stiffness of the surrounding rock support system.The full-length anchorage support method is adopted in the initial stage of roadway support, which has more support initiative, can make more fully use of the strength performance of the anchor bolt, and eliminate the stress concentration of the surrounding rock in time, and has obvious technical advantages.