Numerical Simulation Of Pre-Stressed Yield Bolt Support And Its Application

As a kind of main coal mine roadway supporting methods in China nowadays, bolting has been widely accepted by most people. Due to the mining ages increasing, both new mines and old mines have to exploit coalfields in complex geological conditions or soft stratofabric or deeper deposits. As a result, apparent large deformation, big ground pressure and long-term sustained rheological characteristics of soft rock occur in roadway wall rock. All of these result in much larger deformation roadways that hardly can be controlled by traditional bolting. Pre-stressed yield bolt has extensibility and it is designed specially against roadways large deformation due to deep mining, soft rock and dynamic pressure. It can apply high pre-stress to wall rock and decrease the development of roadway separation layers in high limit. The body of this bolt is made of high-strength steel, so it can support strongly and maintain stabilization of roadways. It is called yield bolt because a tailor-made yield tube is installed between nut and pallet of the pre-stressed bolt. This kind of structure can make the bolt adaptable to large deformation of wall rock of roadway under high resistance pressure for support. Field tests show that the pre-stressed yield bolt is most effectual in controlling large deformation of wall rock of roadway.Under the direction of "first strong later yielding" and "fit strong in yielding" , numerical methods on pre-stressed yield bolt are studied and constitutive equations are built in this paper based on the characteristics of large deformation roadway. A project case that pre-stressed yield bolts are used in a coal mine in Xintai mining area is quoted in this paper and numerical simulation analysis to support to the large deformation roadways of the coal mine is done through finite element calculation software ANSYS. Pre-stress to the bolts is determined by analyzing separation layers of wall rock and yield points of bolts are analyzed and designed based on axial stress on bolts and roadway deformation. At last, support schemes and designs are optimized.