Development Patterns of Fractured Water-Conducting Zones in Longwall Mining of Thick Coal Seams—A Case Study on Safe Mining Under the Zhuozhang River

Feng Du,Rui Gao

doi:10.3390/en10111856

Abstract

The key to the safe mining of thick coal seams under rivers is understanding the development patterns of fractured water-conducting zones (FWCZ) when various mining methods are used. To solve this problem, we employed numerical simulation to investigate FWCZ when slice mining and longwall caving mining are performed. When slice mining was carried out, the maximum height of the FWCZ in the higher slice was 88 m. When the lower slice was mined, the maximum height became 95 m, and the ratio of the fracture height to the coal seam thickness was 15.8. For longwall caving mining, the height of the FWCZ reached 126 m, which was 31 m more than that of slice mining, and the ratio of the fracture height to the coal seam thickness was 21. Through field measurements, the height of the FWCZ during longwall caving mining of thick coal seams was verified. The measured height was 108.87–112.57 m, and the measured ratio was 19.08–19.28. Under the same stratigraphic conditions, changes in the bulking factor and structural stability of key strata were the dominant factors that determined how mining methods affected the height of the FWCZ. These development patterns can provide significant theoretical insights for effectively preventing water hazards on mine roofs.

Highlights

In China, conflicts between coal seam mining and environmental auth-conservation have been increasing
Many researchers have been looking into the topic and obtained numerous theoretical results [4,5,6]
Based on the movement characteristics of the overburden during longwall caving mining, Peng divided the overburden movement into four sections from the bottom to the top: caved zone (A), fractured zone (B), continuous deformation zone

Summary

Introduction

In China, conflicts between coal seam mining and environmental auth-conservation have been increasing. Coal mining is severely threatened by overlying water bodies such as rivers, lakes, and reservoirs. Sudden floods have occurred in many mine shafts when mining is carried out under water bodies [1,2,3]. The major focus of coal mining under water bodies is to thoroughly understand the development patterns of FWCZ when various mining methods are performed. The main coal mining layer of the 7802 face, the Wuyang coal mine, the Lu’an mining area is the 3# coal seam. The immediate roof of the 3# coal seam is middle thick layered black mudstone and sandy mudstone, with an average thickness of 4.30 m. The main roof consists of thick layered medium sandstone, which is

Results

Discussion

Conclusion