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Soil nailed retention- a practical approach to field verification

机译：土钉固位-现场验证的实用方法

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Based on experience gained over the last 20 years of local practice, the authors have concluded: The average grout-to-soil (or rock) adhesion is a critical aspect of the design of soil nailed retention systems and must be confirmed by an appropriate program of field verification testing comprising both preconstruction verification testing and proof testing during construction. Generic test procedures (especially of the cut and paste type) should not be used unless they can be shown to relate to the particulars of the specific design and the assumptions relating to nail adhesion. For permanent soil nail installations the design values should be such that, under normal serviceability conditions, the amount of time dependent movement or creep is minimal and progressively diminishes with time. This can generally be achieved by adopting a Factor of Safety of at least 2 on pullout resistances. Alternatively, if performing a limit state type of analysis, a reduction factor of 0.5 can be applied to the ultimate pullout resistance. Nail adhesion values in weathered siltstone can be greatly reduced if the drill holes are too smooth and this needs to be checked during the initial sacrificial nail test program. Appropriate monitoring of the field drilling of production nails should also be carried out in such materials. Average adhesions in smooth holes can be as little as 10 percent of the adhesions developed in rough holes. Currently the FHWA soil nail guidelines are a useful and comprehensive reference. However, they tend to be very detailed and if implemented fully can add significant cost and delay to projects. Upcoming European Standards (expected later this year) may present a more appropriate testing regime but this waits to be seen. The FHWA procedures for conducting sacrificial nail tests are considered appropriate for local soil nail projects. In addition to the testing procedures and acceptance criteria recommended by the FHWA, the authors consider that the elastic line be used to evaluate test nail performance, particularly with respect to the likely reserve in adhesion above the design values.
机译：根据在过去20年的本地实践中获得的经验，作者得出以下结论：水泥浆对土壤（或岩石）的平均附着力是土钉固定系统设计的关键方面，必须通过适当的程序加以确认。现场验证测试，包括施工前的验证测试和施工期间的证明测试。除非可以证明它们与特定设计的细节以及与指甲附着力有关的假设有关，否则不应使用通用测试程序（尤其是剪切和粘贴类型的测试程序）。对于永久性土钉安装，设计值应确保在正常使用条件下，与时间有关的移动或蠕变量最小，并随时间逐渐减少。通常可以通过在拉拔电阻上采用至少2的安全系数来实现。可替代地，如果执行极限状态类型的分析，则可以将0.5的减小系数应用于极限抗拔力。如果钻孔太光滑，可以大大降低风化粉砂岩中的指甲附着力值，这需要在最初的牺牲性指甲测试程序中进行检查。在这种材料中，还应对生产用钉的现场钻孔进行适当的监控。光滑孔中的平均粘着力仅为粗糙孔中产生的粘着力的10％。目前，FHWA土钉指南是有用且全面的参考。但是，它们往往非常详细，如果完全实施可能会增加可观的成本并延误项目。即将到来的欧洲标准（预计在今年晚些时候推出）可能会提出更合适的测试制度，但这有待观察。 FHWA进行牺牲性指甲测试的程序被认为适用于当地的土壤指甲项目。除了FHWA推荐的测试程序和验收标准外，作者还考虑将弹性线用于评估测试钉的性能，尤其是在高于设计值的情况下可能保留的粘合力方面。

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