1. Project background:

Datong Mining Area is one of China's most important coal production bases. It has rich reserves, a long history of mining and unique "dual-system coal fields". The annual output of raw coal reaches more than 150 million tons, and is known as the "China Coal Capital". The unique geological conditions of the Datong Mine Area, especially the mining of hard roofs and dual-system coal seams, also bring great challenges to tunnel support.

2. Roadway support problems

The mining of extra-thick coal seams (usually referring to coal seams with a thickness of more than 8 meters) in Datong Mining Area faces world-class support problems. This is mainly due to the joint influence of its hard roof, superimposed mining of double-system coal seams, high ground stress and complex geological conditions.

(1) Hard top plate and strong ore pressure appear. The top plates of the extra-thick coal seams in Datong Mine Area are mostly hard thick layers of sandstone, which has strong integrity and joint fissures do not develop. The roof panel is prone to form a large area of ​​overhanging after being harvested. When the exposed area reaches the limit, the roof plate will suddenly break and collapse, causing strong dynamic pressure impact, which poses an extreme test for the tunnel support structure and often leads to severe deformation or failure of the support components. This requires that the support system must have extremely high strength and impact resistance.

(2) High ground stress and strong mining stress. With the increase in mining depth, the stress level of the Carboniferous-Permian extra-thick coal seam increased significantly. At the same time, the mining intensity of the super-thick coal seam comprehensive laying surface is high, and the space for mining is huge at one time will generate extremely high mining concentration stress around the tunnel. Under the superposition of the two stresses, the tunnel has major deformations such as the top plate sinking, the bottom plate bulging and the two violently squeezed. Conventional support may be difficult to effectively control surrounding rock deformation and requires more powerful support techniques and materials.

(3) Complex and changeable geological and surrounding rock conditions. The Carboniferous extra-thick coal seams in the Datong mining area are often invaded by magmatic rocks such as Huang porphyry, causing the coal seams to deteriorate and silicify and the coal body to break down. It is difficult to obtain reliable and stable anchoring force for anchor rods and anchor cables, and the support effect is greatly reduced, and it is easy to cause safety problems such as local falls on the roof and patches./p>

3. Coping strategies

The high-strength anchor cable support system of the extra-thick coal seam tunnel in Datong Mine Area is a systematic project with rigorous parameter design and fine layout. Its core lies in coping with challenges such as high ground pressure and hard top plates through high-strength materials, reasonable parameter design (length, spacing, preload), reliable anchoring methods and effective coordination between anchor rods and anchor cables. In particular, applying a high initial preload force can actively compress the surrounding rock, significantly improve the support effect, and inhibit the disstratigraphic and deformation of the surrounding rock.

4. Application effect

The series of anchor support products produced by Lanyuan Technology have been widely used in the Datong mining area, such as Tashan Coal Mine, Tongxin Coal Mine, Madaotou Coal Mine and dozens of well-industrial mines. Here is a case example:

Tashan Coal Mine is one of the largest well mines in China, with an annual output of raw coal reaching more than 25 million tons. The main quarry is C3-5# coal seam, the average thickness of the coal seam is 15.72m, the coal seam layer is stable, the thickness is large, and the coal seam inclination angle is 3-5°. By using high prestressed anchor cable combination support, combined with W steel belt and metal mesh, grouting reinforcement is used in some areas to effectively control the deformation of surrounding rocks and ensure normal mining of the underground comprehensive mining working surface.

For example, the main supporting materials used in the tape groove of the retrieval working face are: the anchor support adopts yield strength 500MPa, diameter 22mm, length 2500mm, left-hand rebar-free rebar-reinforced anchor support; the anchor cable support adopts tensile strength 1860MPa, diameter 21.8mm, length 8300mm, and JW steel strip.

In general, the practice of high-strength anchor cable support system in the Datong mining area is successful and effective. For example, coal mines such as Tashan and Tongxin have effectively controlled the deformation of tunnels under complex geological conditions of extra-thick coal seams through high preload, high-strength materials and scientific and reasonable combination design, ensuring the safe and efficient production of the mine, and achieving significant economic benefits.

In the future, as mining extends to deeper and more complex conditions, support technology will continue to develop in a direction of higher strength, higher preload, more intelligent monitoring and closer integration with grouting and other modification technologies.