Research on Deformation Mechanisms of a High Geostress Soft Rock Roadway and Double-Shell Grouting Technology

In this study, the deformation characteristics and mechanical properties of coal and rock mass in the S2N5 working face of the Xiaokang coal mine are analyzed to address the problem of large deformation of soft rocks with high in situ stress surrounding roadways. Through a newly developed grouting pipe, a double-shell grouting technology, consisting of low-pressure grouting and high-pressure split grouting, is proposed for the Xiaokang coal mine. In addition, the effect of grouting is evaluated by borehole peeping and deformation monitoring. The results show that the double-shell grouting technology can effectively improve the overall mechanical properties of the surrounding coal and rock mass, preventing the large deformation and failure of the roadway. This technology can be useful when analyzing and preventing large deformation of soft rock roadways.

Exploration and Practice of Pressure Relief by Slotting Coal Seams with a Diamond Wire Saw

To safely and economically eliminate the threat of high geostress in the coal mining process, based on the engineering case study of pressure relief by slotting residual coal pillars at a mine in the Kailuan mining area, a method of pressure relief by slotting coal seams with a wire saw was explored, and numerical simulation was carried out. The results show that the wire saw can cut coal seams in a large area, with a cutting efficiency and slotting depth greater than those of hydraulic slotting; a stress concentration zone forms in front of the wire saw coal cutting working face and a stress reduction zone and a stress recovery zone form behind. The pressure relief range varies, increasing at first and then decreasing. The exploration and practice of pressure relief by slotting coal seams with a diamond wire provides theoretical guidance and practical reference for pressure relief by slotting coal seams.

Rockburst Prediction on the Superimposed Effect of Excavation Accumulation Energy and Blasting Vibration Energy in Deep Roadway

In deep mining, much elastic energy is stored in rock mass due to the high geostress. Rockburst will be induced by accumulated energy during excavation. Meanwhile, because of blasting vibration energy in the host rock, there will be an obvious superimposed effect on the probability and intensity of rockburst. To explore the most reasonable and effective method for understanding rockburst problem under blasting, a deep roadway of Sanshandao gold mine was studied. On the basis of in situ geostress data, the accumulated energy of three-centered arch roadway after quasi-static excavation was derived. Then, a series of in situ blasting vibration were monitored, and the blasting vibration energy was calculated by employing the equivalent theory of elastic vibration boundary. Finally, the tendentiousness of rockburst was evaluated qualitatively with the superimposed energy. The results indicated that the disaster-driven energy was increased by 45.1% and 28.2% on different places of roadway. Also, the probability and intensity of rockburst would be raised.

Construction Technology of Large-deformation High Geostress Soft Rock Tunnel

In the process of tunnel construction, if large-deformation occurs in high geostress soft rock, it will likely cause geological disasters. This situation will not only seriously affect the smooth progress of tunnel construction, but also cause serious safety threat to the construction personnel. Therefore, with the continuous growth in the number and scale of tunnel construction in recent years, the construction technology for high geostress soft rock with large-deformation has begun to receive more and more attention from the society. Based on this, this paper takes an actual project as an example to analyze the specific application of the technology in order to improve the construction effect and avoid the damage caused by the large-deformation of the high geostress soft rock.