Discussion of some rules for prestressed anchors in some technical standards

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.