Discussion of some rules for prestressed anchors in some technical standards
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摘要: 一些技术标准对预应力锚杆的规定存在着一些争议。土层锚杆水平刚度系数公式存在着严重缺陷且意义不明确，建议修改完善。基本试验时：稳载期间稳定指标0.1 mm为笔误，应为1.0 mm；不应减短锚杆锚固段长度，因为锚固段较短时得到的黏结强度偏高；为得到黏结强度极限值，试验最大荷载应为破坏荷载。验收试验不合格时扩大抽检比例宜为不合格锚杆数量的2倍。蠕变试验时蠕变率计算公式应明确计时方法，否则蠕变率指标无意义。不需严格限制自由段长度，可为4～6 m以便更好地控制支护体系变形。临时锚杆设计使用期宜从2年提高到5年，以更好地满足目前工程建设需要。二次注浆在注浆体强度达到5 MPa后进行这条规定很难执行，建议改为在注浆体初凝后终凝前进行。Abstract: There are some controversies on some rules for the prestressed anchors in some technical standards. There exist serious defects in soil anchor level rigidity coefficient formula, and meaning of the formulas is not clear, so we suggest to modify and improve it. In basic tests, the stable index 0.1 mm is a clerical error during the stability load period, it should be 1.0 mm; the anchor length should not be cut short since the shorter anchor gets the too high bonding strength; the maximum test load should be collapse load for the limit bond strength. The expanding detection numbers are suggested to 2 times the unqualified anchor numbers in acceptance tests. The timing method for the creep rate formula should be clear in the creep tests, otherwise the creep rate index would be meaningless. The free length of the anchor needs not be strictly limited, and it should be 4~6 m so as to better control the deformation of support system. The design service life of temporary anchors should be increased to 5 years from 2 years to better meet the needs of engineering now. The rule that the secondary grouting should be made after body strength achieves 5 MPa is hard to execute, so we suggest to make it during the period from the initial setting to the final setting.
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Keywords:
- prestressed anchor /
- stiffness coefficient /
- basic test /
- acceptance test /
- creep test /
- free period /
- anchor design trial /
- secondary grouting
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