Application of Anchor Cable Support in Coal Mining(1)

Introduction

Coal mine roadway support has experienced the development process from wood support, brickwork support, section steel support, anchor rod support to anchor cable support.Anchor cable has the characteristics of large anchorage depth, high bearing capacity and large prestress, which can obtain ideal supporting effect.Anchor cable support technology is widely used in civil reinforcement engineering, and it is more and more widely used in coal mine tunnel.The practice shows that the application of anchor cable has good supporting effect in broken and compound roof roadway, roadway with high ground stress and affected by mining, coal roof roadway with caving, large section roadway and crossing points.With bolt support, the support range of bolt support can be significantly expanded to ensure the safety of roadway.

1. Development process of anchor cable support

As early as 1890, the North Wales coal mine reinforcement project began to use steel bars to reinforce the rock. In 1911, the Bolting support technology was first used in the tunnel in Friedens Coal Mine in the United States. In 1918, the Silesian coal mine in the United States used the bolting support technology first.Since then, the application of anchorage technology began to expand rapidly.In 1978, Tony Barley, a British man, installed an upper anchor at one end of the steel strand and used resin seal as a bearing anchorage section at the other end. Then, 3 such units were connected to a 2 m long steel pipe at a certain distance, and then exerted tension on the steel pipe. Experiments show that this method can disperse the load to the resin sealing section and make the support more firm.In 1988, pressure-distributed anchor cable technology was first applied to clay strata in Southampton, UK, with a bearing capacity of 1337kN.Compared with foreign countries, the development of anchor cable technology in China started relatively late, and the anchor cable support technology began to be applied in China in the 1990s. In 1997, Beijing Well Construction Research Institute and Beijing Mining Research Institute of The Coal Research Institute successfully developed the small hole anchor cable support technology, since then, the anchor cable support technology has been widely used in China.

2. Principle of anchor cable support

2.1 Self-supporting arch

As shown in Figure 1, after the anchor cable is fixed, the concentrated stress of the lock is transferred to the supporting structure with a pressure distribution of 45 degrees. Under the action of prestress, the broken rock mass forms a pressure arch ring, which effectively improves the bearing capacity of the rock mass and makes the surrounding rock more stable.

2.2 Composite beam

Composite beam refers to that when the anchor cable passes through the layered rock, the pressure between the layers of the layered rock increases due to the pretightening force, thus increasing the friction force, improving the integrity of surrounding rock, making it difficult to separate and produce displacement between the rock layers, and increasing the bending strength of the rock layers. The composite beam is the best when the anchor cable and rock stratum are vertical.

2.3 Suspension

Suspension action refers to the unstable rock block is connected with the stable rock mass under the action of anchor cable to prevent its displacement and cause falling danger.