Abstract
The behavior of the overburden of working face 20104 at the Wangjialing coal mine was investigated using borehole imaging. The measured height of the conductive fracture zone (CFZ) in the overburden, 148 m, is significantly different from the height that is predicted by an empirical formula. The spatial relationships between key strata (KS) required for their fracturing and their influence on the CFZ’s height were analyzed. The results demonstrate that the spatial relationships between adjacent KS are a major factor behind the abnormal increase in the height of CFZ relative to the coal seam. The height of linkage (HoL) between KS was introduced and an equation for calculating this height was proposed. The study found that the fracturing of a KS could induce fracturing of the adjacent KS above it if their height difference was smaller than the HoL between them. Otherwise, the fractures resulting from the lower KS would terminate at the bottom of the higher KS. When the location of a high KS satisfies certain requirement, the spatial linkage between adjacent KS will allow for the conductive fractures arising in a lower KS to propagate through the high KS as well as the strata controlled by it, thus increasing the height of CFZ in overburden.
Highlights
The pattern of evolution of mining-induced fractures in overburden is a theoretical basis for preventing water inflow, fire and gas-related disasters, and other mine disasters
Based on the spatial relationships between key strata (KS) required for fracturing them, a set of models were developed to explain the reason behind the large height of the conductive fracture zone (CFZ) induced by thick seam mining
This study analyzed the spatial relationships between KS required for their fracturing
Summary
Peng Li 1 , Xufeng Wang 1,2,3, *, Wenhao Cao 1 , Dongsheng Zhang 1,4 , Dongdong Qin 1 and Hongzhi Wang 1. Key Laboratory of Deep Coal Resource Mining, China University of Mining & Technology, Xuzhou 221116, China
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