Interpretation of pull-out tests on instrumented rock bolts by means of 3D numerical modelling

摘要

The study deals with the interpretation of in situ pull-out tests on instrumented grouted rock bolts, which took place at the ANDRA underground research laboratory of Meuse/Haute-Marne (France). It aims at characterizing the behaviour of a single rock bolt in argillite, taking into account both the different materials (bolt, argillite, grout) and the different interfaces (argillite/grout and grout/bolt). 6 tests were carried out in situ, on two types of bolts: 3 tests on HA-25 rock bolts, and 3 tests on CT-Bolt rock bolts. For each kind of rock bolt, one short term and two long term pull-out tests were performed. The paper focuses on the interpretation of the long term tests. During these tests, the end of the bolt is pulled with different successive load stages, each load being maintained constant during various times. Two different loading paths were considered in this work. During the tests, the displacement of the head of the rock bolt is classically measured. In addition, in the tests considered in this work, the bolts were instrumented with axial strain gauges, fixed to the rock bolts every 15 cm, so that the axial strains are recorded during the whole test (as well as before the test) along the grout/bolt interface. In addition to the in situ pull-out tests, laboratory tests were carried out in order to characterize the mechanical behaviour of the grout.