预应力锚索的特征荷载包括锚索工作荷载与极限荷载,是判断锚索锚固效果的重要依据。基于6组预应力锚索原位拉拔破坏试验,依据拉拔荷载-位移全过程增量曲线研究预应力锚索荷载传递机制,提出了预应力锚索特征荷载的判定方法。研究表明:锚索受力全过程分为外锚段紧固、外锚段拉拔、自由段拉拔、锚固段滑移4个阶段;锚索工作荷载以锚索自由段拉拔阶段转折区间为基础,取其区间中值;锚索极限荷载以拉拔曲线增量位移陡增点为依据,为单级增量位移3 mm左右对应的荷载。最后建立锚索拉拔试验数值模型,分析了在位移陡增点前后两级拉拔荷载下锚索-注浆体、锚固耦合体-岩层界面锚固段剪应力分布规律,验证了所提出的极限荷载位移判据的准确性。
Abstract
Composed of working load and ultimate load, the characteristic load of prestressed anchor cable is a critical basis for judging the anchoring effect of anchor cables. The load transfer mechanism of prestressed anchor cable is examined according to the load-incremental displacement curve obtained from six groups of in-situ pull out destructive tests. The method of determining the characteristic load of prestressed anchor cables is also proposed. The whole process of cable in pull load are divided into four stages: the fastening of external anchor segment, the drawing of outer anchor segment, the drawing of free segment, and the sliding of anchorage segment. The working load of anchor cable is determined as the average value between the upper and lower limits of the inflection point of the stage of free segment drawing, while the ultimate load is determined according to the steep increment point of pull-out curve, corresponding to that at incremental displacement 3 mm. In addition, numerical model of the pull-out test is also established using FLAC3D to analyze the shear stress distribution of cable-grouting body and coupling body-rock interface in anchored segment, verifying the accuracy of the ultimate load displacement criterion.
关键词
特征荷载 /
预应力锚索 /
拉拔试验 /
数值模型 /
荷载-增量位移曲线
Key words
characteristic load /
prestressed anchor cable /
pull-out test /
numerical model /
load-incremental displacement curve
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基金
国家自然科学基金项目(41272285);国家重点研发计划项目(2018YFC1504801)
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