Self drilling hollow bar support is an active form of support, the support has the advantages such as low cost, fast supporting speed, low labor intensity, especially greatly simplifies the mining working face end support and advanced support technology, provides security for the rapid development of coal mining face. It is an important supporting technology for coal mine development in recent years.
The problems existing in the tail of the self drilling hollow anchor rod is prominent in the period of application process,due to eccentric load, the tail of the strength is not enough, the extension rate is not enough, leading to the supporting effect of variation, for this problem, the high strength thick tail self drilling hollow bolt anchor tail through special processing, the tail of the grain refinement to improve the shape and intensity of the self drilling hollow anchor bolt’s tail, brittle increase caused by defects in the heat treatment process has changed before, not only improves the anchor tail strength, but also improve the elongation of self drilling hollow anchor bolt’s tail . Field applications have also proved that this technology has greater advantages.
The machining precision of self drilling hollow anchor bolt’s screw friction is not high has influence on the self drilling hollow anchor bolt’s pre tightening force ,which is small to a large extent, improve the machining precision of hollow anchor bolt ‘s screw tail, the tail in coating lubricating oil can effectively eliminate the friction loss, reduce the loss of torque in friction, improve the pretightening force. Lubricating oil needs to be operated separately, increasing the operation process, and can not fundamentally solve the friction of the thread. Only by improving the accuracy of thread processing can the friction at the tail of hollow anchor bar ‘s thread be reduced fundamentally.