Inorganic Cement Grouting for Reinforcing Triangular Zone of Highly Gassy Coal Face with Large Mining Height

Bin Song,Gangwei Fan,Dongsheng Zhang,Wei Yu,Qiang Zhao,Shuaishuai Liang,Shuai Zhang

doi:10.3390/en11102549

Abstract

Aiming to address the serious problem of coal wall spalling in the triangular zone of the coal face end under high-intensity mining, this paper introduces inorganic cement grouting reinforcement technology for medium-depth holes based on the specific geological conditions of the Sihe coal mine in China. Firstly, the effects of different water-to-material ratios and various accelerators on setting time and uniaxial compressive strength (UCS) of grouting materials and consolidation coal are studied. The results show that the combination of 2% accelerator I, 0.3% accelerator II, and 3.0% accelerator III was the most effective. Then, FLAC3D numerical simulation software was used to analyze the distribution laws of the plastic zone, the lateral abutment pressure, and abutment stresses in the face ends during repeated mining. The results indicate that the zone within 25–65 m of the front of the coal face was initially affected by the front abutment pressure. In this area, the stress value decreased slowly and fracture development was relatively intense. Grouting with high pressure and a large flow rate should be used in this scenario as the industrial experiment results indicated that the proposed inorganic cement grouting reinforcement technology could effectively control coal wall spalling and provide technical support for safe and efficient mining.

Highlights

In China, with the development of fully-mechanized mining equipment and the progress in surrounding rock control theories during high-intensity mining processes, fully-mechanized technologies for high mining heights are being widely used in underground mining, given their high resource recovery rates, high coal face yield, and ease of gas control [1–5]
The results indicate that as the coal face continued to advance, the advance abutment pressure distribution large mining height coal face divided into the typical increasing, decreasing, distribution ofofthe the large mining height coalcould face be could be divided into the typical increasing, and stable areas
Through observation and comparison of the amounts of coal wall rib spalling before and after grouting, we found that rib spalling occurred frequently in the face ends before grouting reinforcement

Summary

Introduction

In China, with the development of fully-mechanized mining equipment and the progress in surrounding rock control theories during high-intensity mining processes, fully-mechanized technologies for high mining heights are being widely used in underground mining, given their high resource recovery rates, high coal face yield, and ease of gas control [1–5]. Affected by multiple mining activities, the stress states of the surrounding rocks are complex and the strata behaviors are more violent in the face ends. Rib spalling can cause roofs to fall, further exacerbating rib spalling. This vicious cycle affects the advance velocity of the coal face, and poses a direct threat to the safety and security of production. Coal and rock stability in the face ends is of great significance for the safe and efficient production of the coal face under high-intensity exploitation [6–10]

Results

Discussion

Conclusion