Mechanical characteristics and field application of flexible bolt under long-term load

The control technology based on combined strengthening support is the main means to control the surrounding rock of the deep coal roadway at present. The complicated supporting form obviously reduces the driving efficiency of roadway and the contradiction between coal mining and roadway driving is very serious,which has become a common problem restricting the high efficiency mining of coal mine. The flexible bolt,which is not limited by the height of roadway and can be installed quickly,has shown good mechanical properties under static tension,which can effectively solve the problem of mutual restriction between roadway safety and driving efficiency. In order to study the mechanical characteristics and dynamic change characteristics of the flexible bolt under long-term load,the flexible bolt was loaded for up to five months through the self-developed bolt (cable) durability test system,and three similar engineering environments were set up without treatment control group,different water pouring environment and different installation angle,and the tensile test of the long-term loaded flexible bolt was carried out. The test results show that the mechanical properties of untreated flexible bolts are less affected by long-term loading compared with those without long-term loading,and the peak value of the flexible bolt is only 1. 2% lower. In the water pouring environment,the flexible bolts are rusted in many places,and its peak load and extension performance are reduced respectively by 8. 6% and 21. 4% ,while the flexible bolts treated with antirust can maintain its own mechanical performance. The flexible bolts with different installation angles have different mechanical behavior,and when the angle is too large,the bearing capacity of the flexible bolt will be adversely affected. In the field application,it is necessary to ensure that the flexible bolts must be treated with antirust and its installation angle should not be too large. Finally,the field test of the flexible bolt single support technology is carried out in the roadways with complex condition such as large inclination strong dynamic pressure roadway,high stress large section roadway and thick top coal roadway. The efficiency of bolt support and the driving speed of roadway have been significantly improved,and the deformation of surrounding rock is effectively controlled.