向家坝水电站尾水洞出口预应力锚杆施工技术

Construction technology of prestressed anchor in tailrace tunnel outlet of Xiangjiaba Hydropower Station

向家坝水电站右岸尾水主洞出口部位围岩稳定性较差,为保证出口顺利下挖,采用了混凝土护壁和预应力锚杆相结合的措施进行支护加固。其中预应力锚杆采取"锚固段灌注速凝水泥卷式锚固剂、张拉段灌注缓凝砂浆、用扭力扳手进行张拉"的施工技术,利用内外段凝结时间差,实现了预应锚杆的快速张拉。经超声波无损检测,锚杆张拉段周边砂浆的密实度达90%以上,取得了良好的锚固效果。对整个施工过程和技术要点进行了详细介绍和总结。

As the instability of the surrounding rock of tailrace tunnel outlet of Xiangjiaba Hydropower Station on right bank,we use concrete retaining wall combining with prestressed anchor as reinforcement in order to ensure the smooth progress of excavation.We fill the inner anchoring section with quick-solidified rolled cement anchoring agent,the tensile section of the prestressed anchor bar with retarded cement mortar,and then the bar is tensioned with torque wrench.The consolidation time difference between inner section and outer section is utilized to realize the quick tensile of prestressed anchor.Through non-destructive testing,the compactness of mortar in the surrounding of tensile section is over 90%.By this construction technology,satisfied anchoring effect has been achieved.We give a detailed description and summarization of the key technological points in the construction process.