Abstract

The primary problem needed to be solved in mining close coal seams is to understand quantitatively the floor failure depth of the upper coal seam. In this study, according to the mining and geological conditions of close coal seams (#10 and #11 coal seams) in the Second Mining Zone of Caocun Coal Mine, the mechanical model of floor failure of the upper coal seam was built. Calculation results show that the advanced abutment pressure caused by the mining of the upper coal seam, resulted in the floor failure depth with a maximum of 26.1 m, which is 2.8 times of the distance between two coal seams. On this basis, the mechanical model of the remaining protective coal pillar was established and the stress distribution status under the remaining protective coal pillar in the 10# coal seam was then theoretically analysed. Analysis results show that stress distribution under the remaining protective coal pillar was significantly heterogeneous. It was also determined that the interior staggering distance should be at least 4.6 m to arrange the gateways of the #209 island coalface in the lower coal seam. Taken into account a certain safety coefficient (1.6–1.7), as well as reducing the loss of coal resources, the reasonable interior staggering distance was finally determined as 7.5 m. Finally, a novel method using radon was initially proposed to detect the floor failure depth of the upper coal seam in mining close coal seams, which could overcome deficiencies of current research methods.

Highlights

  • Coal has a share of more than 90% in the fossil fuel resources of China, and this trend will not change significantly in the short term (Michieka, 2014)

  • After the mining of the upper coal seam (UCS), gateways of the lower coal seam (LCS) will be arranged after the roof caving been stable

  • After mining of the #10 coal seam in the Second Mining Zone (SMZ), stresses at different levels will concentrate in the remaining protective coal pillar (RPCP) with 18 m width, and transfer to the lower strata

Read more

Summary

Introduction

Coal has a share of more than 90% in the fossil fuel resources of China, and this trend will not change significantly in the short term (Michieka, 2014). After the mining of the UCS, gateways of the LCS will be arranged after the roof caving been stable This method does not account effects of the FFD of UCS and the stress concentration in RPCP. After mining of the #10 coal seam in the SMZ, stresses at different levels will concentrate in the RPCP with 18 m width, and transfer to the lower strata. It will directly affect the gateways arrangement of the #209 island coalface in the #11 coal seam. It can be initially determined that the stress-relaxed area exists at locations where the distance to edges of the RPCP is larger than 4.6 m through calculation using the approximate average values. Taken into account a certain safety coefficient (1.6–1.7), as well as reducing the loss of coal resources, the reasonable ISD for the gateways of the #209 island coalface was determined as 7.5 m (Figure 5)

Discussion
Findings
Conclusions
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call