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  • Performance of fully encaps...
    Chen, Yu; Li, Charlie Chunlin

    Tunnelling and underground space technology, January 2015, 2015-01-00, 20150101, Letnik: 45
    Journal Article

    The ultimate displacement of the D-Bolt is more affected by the displacing angle α than the rebar bolt. Display omitted •An approach was developed to apply pull-and-shear loading to rockbolt.•The performance of rebar and D-Bolt was examined in the laboratory.•The displacement capacity of D-Bolt depends on the displacing angle.•The displacing angle is different from the loading angle. The performance of two types of rock bolts, fully encapsulated rebar and D-Bolt, under combined pull and shear loading were studied in the laboratory. A new test approach was developed to apply the pull and shear loads to the rock bolt at the same time so that the bolt is displaced in a direction different from the bolt axis. Five displacing angles between 0° (pure pull) and 90° (pure shear) were employed in the tests. The test results show that the linear elastic stiffness of both the D-Bolt and the rebar bolt is mobilised quickly after a small displacement. When the displacing angle is larger than 40°, grout crushing may occur underneath the bolt shank, resulting in reduction in the stiffness of the bolt. The ultimate load of the bolts remains approximately constant no matter what the displacing angle is for both the D-Bolt and the rebar bolt. The displacement capacity of the D-Bolt, however, is dependent on the displacing angle. The ultimate displacement of a 1-m long D-Bolt section varies from 140mm under pure pull (0°) to approximately 70mm when the displacing angle is larger than 40°. The ultimate displacement of the rebar slightly increases from 29mm under pure pull to 53mm under pure shear. In general, the displacement capacity of the D-Bolt is larger than that of the rebar bolt. It is approximately 3.5 times the rebar under pure pull and 50% higher than rebar under pure shear. The test results show that the displacing angle of the bolt is larger than its loading angle, which is also confirmed by the analytical solutions.