Rock bolt mine support is a key technology in coal mining. Rock bolt mine support materials play a vital role in rock bolt mine support technology. Supporting materials with superior performance are the necessary prerequisite for giving full play to rock bolt mine support effect and ensuring roadway safety. Today, we will introduce the relevant precautions for the use of anchor rods, so that you can have a better understanding of anchor rods.
(1) The tail of anchor rod is the most complex and easily damaged part in the whole rod body. The stress analysis of bolt thread section is carried out, and it is found that the stress concentration of thread section is 2-3 times locally due to diameter change Because the spherical rotation center between the tray and the ball pad is unreasonable, self-locking occurs between the two spherical surfaces, which makes the stress of the anchor bolt deteriorate sharply and even break.
(2) Tension-bending-torsion, tension-shearing-torsion, and combination of tension-bending-shearing-torsion are common stress states in the process of underground anchor installation, and the stress increases closer to the fixed end, so the most unfavorable position is the fixed end.
(3) When the installation angle of anchor rod is too large and the tensile stress reaches a certain value, long-term loading will cause the thread section at the tail of anchor rod to bend and crack or even break; When the pre-tightening torque is greater than 600N'm, the composite stress of the bolt is close to the yield stress of the material, and the bolt cracks from the bend first, and then the crack expands, causing the bolt to break before reaching the breaking force.
(4) Some optimization schemes are put forward, such as vertical setting of corner bolt, redesign of self-aligning ball pad, full-length anchoring of pre-stressed bolt, and adjustment of pre-tightening torque of bolt to 400N.m, so as to reduce the influence of harmful force on the rod body.
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