Integrated study on stability judgment method for grouting anchor tests

The researches on the judgment methods for displacement stability of grouting bonded anchors with various loading tests in cohesive soil layer show that: (1) The interface creep between anchor grout and strata follows the creep mechanism, and the determination of displacement stability of anchor head is to determine whether the interface creep is stable essentially. (2) Stable creep occurs at the interface when the load is relatively small, and creep failure occurs when the load exceeds the critical one. The complete failure process can be divided into three stages: initial, sustained and accelerated. The stability should be determined according to the creep characteristics of the sustained stage rather than the data of the initial stage. (3) About two-thirds of the anchor creep failure forms are abrupt, and the rest are slow, which corresponds to three kinds of creep curve forms. (4) The displacement threshold for stability judgment should not be less than 0.1 mm, the unit period should not be shorter than 10 min, and the displacement increment cannot be directly used for stability judgment. (5) In stability judgment, it should be determined qualitatively that the creep rate is slowing down on the whole, and quantitative indicators should be determined to keep the rate at a low level so as to make the displacement convergent. (6) The stability judgment should mainly be based on the parameters with dual attributes of displacement and time. Its accuracy of the creep variable in the unit period is relatively high, and the creep rate of 2.0 mm is applicable in any case. (7) The creep rate of 2.0 mm as the internal principle of the recommended stability judgment method is suitable for all kinds of applications and various types of bonded anchors, all kinds of loading tests and all kinds of loading and unloading methods such as rapid method.