Experimental Study on Anchorage Performance of Improved Self-locking Prestressed Anchor Cable

To address the issues of excessive deformation and prestress loss caused by stress concentration at the external anchor head of traditional prestressed anchor cables in fragmented rock slope reinforcement, an improved self-locking prestressed anchor cable was developed by innovating the clip structure of the self-locking device to enhance anchoring performance. Laboratory tensioning and locking tests were conducted to verify the mechanical locking effect of the improved anchor cable. Subsequently, a typical fragmented rock slope project in Zhangjiajie, Hunan Province, was selected for in-situ tensioning and locking tests. Distributed optical fiber sensing testing technology was employed to monitor the entire tensioning and locking process along the full length of the grout for three improved self-locking tension-type prestressed anchor cables. The axial strain distribution patterns of the grout at various stages were obtained, and the shear stress distribution was derived. Simultaneously, the strain of the steel pipe within the self-locking device was tested and analyzed. The results indicate that during the tensioning process, the inner anchorage section exhibits the typical mechanical characteristics of a tension-type anchor cable. The axial strain gradually develops from the proximal end of the inner anchorage section and continuously propagates backward as the load increases. At this stage, the self-locking device has no influence on the stress state of the inner anchorage section. Within 24 hours after unloading and locking, the strain distribution of the self-locking anchorage section remains stable without significant prestress loss, demonstrating excellent anchoring and locking efficacy. Because the test anchor cable comprises two anchorage units, the interaction between these units causes notable tensile strain, negative shear stress, and an increase in shear stress at the distal end of the M_S1 unit. Affected by uncertainties such as on-site construction and measurement, the shear stress distribution is uneven, with a peak value of approximately 0.3 MPa, and the peak position of the M_S2 unit is slightly posterior to that of the M_S1 unit. In addition, the strain of the self-locking steel pipe starts from the end of the dedicated anchorage and gradually transitions from compressive strain to tensile strain with increasing distance; the strain value increases proportionally with the tensioning load. These findings provide a reference for further optimizing the support structures of fragmented rock slopes and enhancing the anchoring performance of self-locking prestressed anchor cables.