Experimental Study on Anchorage Performance of Improved Self-locking Prestressed Anchor Cable
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摘要:
为解决传统预应力锚索在破碎边坡加固中，因外锚头应力集中导致变形过大及预应力损失的问题，对自锁型预应力锚索进行改良，创新自锁器夹片结构以提升锚固性能. 通过室内张拉锁定试验，验证改进型自锁预应力锚索的机械锁定效果；选取湖南省张家界某典型破碎边坡工程，开展现场张拉锁定试验. 现场试验中采用分布式光纤传感测试技术，对 3 根改进型自锁拉力型预应力锚索的注浆体全长进行张拉和锁定全过程测试，获取注浆体在各阶段的轴向应变分布规律，并推导得到剪应力分布情况，同时对自锁器钢管应变进行测试分析. 研究结果表明：改进型自锁预应力锚索张拉过程中，内锚固段表现出拉力型锚索的典型受力特征，轴向应变从内锚固段近端逐渐发展，并随荷载增加不断向后推移，此阶段自锁器对内锚固段的受力状态无影响；卸载锁定后 24 h内，自锁锚固段的应变分布保持稳定，未出现显著预应力损失，锚固锁定效果良好；由于试验锚索包含2个锚固单元，单元间的相互作用使 MS1 单元远端出现明显的拉应变、剪应力负值及剪应力增高等现象；受现场施工、测量等不确定性因素影响，剪应力分布不均，峰值约为 0.3 MPa，且 MS2 单元的峰值位置相较于 MS1 单元略为靠后；自锁钢管的应变从专用锚具一端开始，随距离增加从压应变逐渐变为拉应变，应变值随张拉荷载增大而增大. 研究结果为进一步优化破碎边坡支护结构、提升自锁预应力锚索的锚固性能提供参考.
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关键词:
- 破碎边坡 /
- 自锁型预应力锚索 /
- 张拉锁定试验 /
- 现场试验 /
- 分布式光纤传感测试技术
Abstract: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 MS1 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 MS2 unit is slightly posterior to that of the MS1 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.
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图 1 改进型自锁预应力锚索的2种类型示意
Figure 1. Schematic diagram of two types of improved self-locking prestressed anchor cables
图 8 锚索张拉时注浆体应变分布曲线
Figure 8. Strain distribution curves of grout during tensioning of anchor cables
图 9 锚索卸载后注浆体应变分布曲线
Figure 9. Strain distribution curves of grout after unloading of anchor cables
图 10 自锁锚固段剪应力分布曲线
Figure 10. Shear stress distribution curves of self-locking anchorage section
图 11 1号锚索钢管应变分布曲线
Figure 11. Strain distribution curves of steel pipe of No. 1 anchor cable
图 12 2 号锚索钢管应变分布曲线
Figure 12. Strain distribution curves of steel pipe of No. 2 anchor cable
表 1 试验场地岩土体力学性质指标
Table 1. Mechanical property indexes of rock and soil mass at test site
土类名称 重度γ/
（kN•m−3）黏聚力c/
kPa内摩擦角
φ/（°）粉质黏土 18.7 45 15 强风化泥质页岩 22.1 60 20 中风化泥质页岩 24.3 90 30 
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表 2 分布式光纤相关参数
Table 2. Relevant parameters of distributed optical fiber
参数 数值 最大拉断力/N 2350 弹性模量/GPa 42 工作温度/（℃） −20～85 可承受最大围压MPa 100
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