Stressed characteristics and regional anchoring mechanism of cable bolts in coal mine roadway roof

The cable bolts are the main supporting material for controlling the surrounding rock of the coal mine roadway. As the mining depth increases，the stress environment of the surrounding rock of the roadway deteriorates，and the roof cable bolts breaking problem is more prominent，which can easily lead to roof collapse accidents and seriously affect production safety. To solve the problems of the high breaking rate of cable bolts in coal mine roadway roof and difficult to realize stability control of layered roofs，numerical simulation，theoretical analysis and field test are comprehensively adopted. In this paper，the real stressed characteristics of cable bolts in different areas of roadway roofs and the supporting effect of long and short cable bolts in the roof are studied. Moreover，the anchoring mechanism of the cable bolts in roof in different areas is analyzed. The results show that there is a significant difference in the force distribution of the cable bolt arranged in different areas. It sees that the cable bolt force in the lower roof strata is more complex and bears both tensile and shear loading at the same time. The closer to the middle of the roof，the greater the axial tension on the cable bolt，and the closer to the roadway corner，the more significant the shear load on the cable bolt. It can be concluded that increasing the pretension force of the cable bolt is beneficial to realize the stability control of the roof and uniformity of forces on cable bolts，reduce the disadvantageous force. The increase of the cable bolt length is beneficial to expand the supporting range of the roof，but the surrounding rock supporting stiffness in the anchoring range of the short cable bolt is better than that of the long cable bolt. The roadway roof can be divided into three areas laterally，that is，a central area and two shoulder corner areas. The long cable bolts are preferentially arranged in the central area，which mainly control the deflection and separation of the roof. The short cable bolts are arranged in the shoulder corner areas，which mainly control the interlaminar shear dislocation of the roof. The roadway roof can be divided into three layers vertically，namely，the unstable layer，sub-stable layer and stable layer. Based on the regional anchoring mechanism of roof cable bolts，a multi-level support technology dominated by long and short cable bolts is proposed，and it has achieved a good engineering application effect in the field.