预应力端锚锚杆全锚后承载分布特征分析

为了分析锚固方式对锚杆承载特征的影响程度，便于巷道锚杆支护设计选型，本文采用理论分析和现场实测的方法，对比了全锚锚固和端部锚固条件下锚杆轴向力与剪应力分布特征。研究结果表明：锚杆承载分布特征与锚固条件、预应力、锚杆直径和围岩强度等密切相关；锚杆轴向力沿锚固段呈现单向递减趋势，锚杆剪应力沿锚固段呈现先增大后减小趋势，主要分布于锚固段400 mm范围内；在受岩层离层错动影响时，轴向力是约束围岩破坏的主导因素，剪力中性点呈现逐步向外侧转移的趋势，相较于端部锚固，全长锚固后锚杆对围岩变形和破坏敏感度更高，应力承载范围集中在离层破坏区域，应力峰值明显降低，应力分布更均匀平缓。研究结果可知：全长锚固可明显提升围岩-支护系统整体强度和刚度，在巷道支护初期就采用全长锚固支护方式，更具有支护主动性，可以更充分利用锚杆强度性能，及时消除围岩应力集中，技术优势明显。

The load characteristics analysis of pre-stressed bolt under end anchored after fully anchored

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.