A new deformable cable for rock support in high stress tunnel: Steel pipe shrinkable energy-absorbing cable

High stress in surrounding rock will lead to serious problems, e.g., rock burst in hard rock and large deformation in soft rock. The applied support system under high in-situ stress conditions should be able to carry high load and also accommodate large deformation without experiencing severe damage. In this paper, a specially designed energy-absorbing component for rock bolt and cable that can solve the above problems was proposed. The energy-absorbing component can provide support resistance by plastic deformation of the metal including constraint annulus and compression pipe. For practical engineering, two forms were proposed. One was installed in the surrounding rock by reaming, and the other was installed directly outside the surrounding rock. During the dilation of the surrounding rock, the relative displacement of constraint annulus and compression pipe occurs, resulting in deformation resistance. Deformation resistance is transmitted to the rock bolt or cable, providing support resistance. The lab test and numerical simulation showed that the energy-absorbing component can perfectly achieve the large deformation effect, the deformation amount is as high as 694 mm, and the bearing capacity is stable at 367 kN. The field application tests were carried out in the mining roadway of Xinjulong coal mine, and the results showed that the new type of cable can ensure itself not to break under the condition of large deformation of the surrounding rock. The energy-absorbing component has the superiorities of performing large constant resistance and controllable deformation to effectively control the unpredictable disasters such as large deformation in soft rock and rock burst in hard rock encountered in deep strata.