Research and engineering application of high pre-stressed resistance enhancement large deformation bolt in deep soft rock roadway

In order to overcome the support problem of large deformation and the high repairing rate of deep soft rock roadway,a new type of high pre-stressed increase-resistance large deformation bolt is developed based on previous studies. It is mainly composed of pallet,metal clip,rod body 1,rod body 2,connection sleeve,cone-thimble and sliding sleeve. Initial pre-stress applied on the new bolt can reach 120 kN,the let-point-pressure can be controlled to 180-240 kN,the deformation can be adjusted flexibly within 150-1 000 mm. In the process of deformation,it can maintain a high level of increasing support resistance. Static tensile tests in laboratory show that compared with the traditional bolt,the new bolt has excellent characteristics of “first to support,then let the pressure,the last continue to support, prevent the fracture and increase the resistance”. In order to further study the mechanical support mechanism of the new bolt,the CABLE unit of FLAC 3D numerical simulation software is secondarily developed by using Fish language programming,and the axial tensile mechanical behavior of large deformation bolt is simulated with high precision. Re- search on the deformation mechanism of a typical deep large deformation soft rock roadway -500 m hydrophobic road- way at Jinyang coal mine in China shows that the low strength of surrounding rock,high ground stress and low initial pre-stress of bolt are the main factors leading to its deformation. It has been unable to solve the outstanding contradic- tion among the three by using the traditional bolt support. In order to maintain the stability of roadway surrounding rock,it is necessary to strengthen the support strength for reducing the deformation rate of surrounding rock and impro- ving the ability of supporting members to adapt to the large deformation of surrounding rock. To verify the support effect of new bolt,a new “ bolt-mesh-spurting” support technology with the core of new high pre-stressed increase- resistance large deformation bolt is proposed,according to the deformation characteristics and mechanism of surround- ing rock in typical deep soft rock roadway of -500 m water discharging gateway in Jinyang coal mine. Numerical simu- lation and field monitoring results show that the new supporting scheme can effectively improve the stress state of bolt and reduce the deformation of surrounding rock,the final deformation of surrounding rock decreases by nearly 60%compared with the original support scheme.