Theoretical model of the double constant-resistance-large-deformation bolts under impact load

In order to guide the support of the surrounding rock mass with constant-resistance-large-deformation (CRLD) bolts under the dynamic disaster during the engineering mining, a theoretical model is established for the double CRLD bolts acting in parallel under the impact load.The model is based on the principle of parallel support of the double CRLD bolts and the Hopkinson impact tensile test of the double CRLD bolts.Moreover, the reliability and correctness of the theoretical model are verified by the comparison to the test results.The displacement-time relation and the load-displacement relation of the double CRLD bolts are further obtained.The research shows that the double CRLD bolts acting in parallel undergoes three stages under the impact load:initially elastic deformation, structural deformation and late elastic recovery.Firstly, the elastic deformation occurs through the stretching of the shank bar.When the internal force of the shank reaches the constant resistance of the CRLD bolts, the structural deformation begins to occur by the relative slippage of the sleeve pipe and the shank rod.Once the velocity of the sleeve is reduced to zero, the structural deformation is completed and the sleeve and the shank rebound together.In addition, the displacement peak of the double CRLD bolts obviously lags behind the load peak under the impact load.