Study on Pressure Relief Technology of High-Pressure Water Jet of Residual Coal Pillar in Overlying Goaf in Close Seam Mining

Shang Yang,Jun Wang,Shuhao Yang,Guangzheng Xu,Xuehui Li,Zhen Shen,Jianwei Cheng

doi:10.1155/2022/7842921

Shang Yang, Jun Wang + Show 5 more

Open Access

https://doi.org/10.1155/2022/7842921

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Abstract

To solve the problem of strong ground pressure behaviour under a residual coal pillar in the overlying goaf of a close-distance coal seam, this paper proposes the technology of weakening and relieving the residual coal pillar in the overlying goaf by a high-pressure water jet. Based on the geological occurrence of the No. 3 coal seam and mountain No. 4 coal seam in the Yanzishan coal mine, the high-pressure water jet pressure relief technology of residual coal pillars in the overlying goaf of close-distance coal seams was studied by theoretical analysis and field industrial tests. First, the elastic-plastic zone of the residual coal pillar and the stress distribution law of the floor are obtained by theoretical analysis, and the influence degree of the residual coal pillar on the support of the lower coal seam working face is revealed. Then, a high-pressure water jet combined with mine pressure is proposed to weaken the residual coal pillar. Finally, through the residual coal pillar hydraulic cutting mechanical model and “double-drilling double-slot” model, the high-pressure water jet drilling layout parameters are determined, and an industrial field test is carried out. The single knife cutting coal output and 38216 working face hydraulic support monitoring data show that high-pressure hydraulic slotting can weaken the strength of the coal body to a certain extent, destroy the integrity of the residual coal pillar, cut off the load transmission path of the overlying strata, and reduce the working resistance of the hydraulic support under the residual coal pillar to a certain extent, which is beneficial to the safe mining of the working face.

Highlights

In recent years, with the increase in coal mining intensity and mining depth, the occurrence conditions of coal seams have become more complex, the mining environment has worsened, and underground engineering disasters have become prominent [1,2,3]
The measures used to address the problem of strong mine pressure behaviour under the residual coal pillar in an overlying goaf mainly include coal seam directional blasting [9] and hydraulic fracturing [10]. rough the above treatment methods, the overall structure of the coal body can be destroyed, the strength of the coal body can be weakened, the connection form of the rock structure can be changed, the stress distribution form of the floor of the residual coal pillar can be improved, and the purpose of stress concentration can be alleviated. e above methods have been widely used in China because the geological conditions of different mining zones are different, the effect is different, and there are some disadvantages
There are many secondary fractures in the remaining coal pillar, and the high-pressure water loss is fast; it is not easy to form the residual coal pillar damaged by pressure

Summary

Introduction

With the increase in coal mining intensity and mining depth, the occurrence conditions of coal seams have become more complex, the mining environment has worsened, and underground engineering disasters have become prominent [1,2,3]. Based on the mining conditions of working faces 38216, 48216, and 48218, theoretical analysis is used to study the failure characteristics and the stress distribution law of the residual coal pillar floor in the overlying goaf and reveal the influence degree of the residual coal pillar on the support of the lower coal seam working face. Failure zone I, plastic zone II, and elastic zone III form from the outside to the inside, in which the elastic zone is the main bearing zone and the main medium for the downward transmission of the overlying load In this part, combined with the mining conditions of the 48216 and 48218 working faces, and based on limit equilibrium theory [6], the elastic-plastic zone range of the residual coal pillar is analysed, and the elastic-plastic zone width of the residual coal pillar is obtained.

B Figure 5

Determination of Coal Pillar Width Direction Drilling

Field Implementation

Conclusion