On-Site Radon Detection of Mining-induced Fractures from Overlying Strata to the Surface: A Case Study of the Baoshan Coal Mine in China

Abstract

Large-scale longwall mining of shallow coal seams may cause mining-induced fractures that can project completely through to the surface. This could lead to a series of mine safety and environmental issues, further deteriorating the already fragile ecological environment in the Western mining areas in China. Therefore, an accurate and effective understanding of the spatiotemporal evolution law of mining-induced fractures in overlying strata and its relationship to upper aquifers is critical. In this paper, the application of the geophysical-chemical properties of radon in mining engineering is explored as a potential solution to the shortcomings of existing surveying methods. A radioactive measurement method is proposed for the detection of the development of mining-induced fractures from overlying strata to the surface in the Baoshan Coal Mine (BCM). The on-site test indicated that the first weighting step is approximately 60 m, the average periodic weighting step is approximately 20 m, and the influence coverage of the advanced abutment pressure is approximately 30 m. The presented method could be used OPEN ACCESSEnergies 2014, 7 8484 as an indirect technical support to increase the safety of coal mining by acting as a simple, fast, and reliable method of detecting mining-induced fractures in overlying strata.

A Novel Caving Model of Overburden Strata Movement Induced by Coal Mining

“…As the shields (hydraulic supports) move, the mine roof behind them continues to cantilever and caves into the mine void, which experiences the process of elastic deformation, plastic deformation, and failure [16,20], producing two types of tensile fractures at the surface over the panel: static tensile fracture above the side of a panel and dynamic tensile fractures that follow behind the advancing face [16,17]. The dynamic tensile fractures close as a result of compressional stress after the advance of the face, and static tensile fractures remain open for several months after mining [17], Currently, a variety of methods, ranging from analytical methods and field experiments to numerical and physical simulation, have been used that mainly focus on the mining-induced effects on the movement of overburden strata, the generation of fractures, and subsidence [2,13,29,30,[45][46][47]. However, very few detailed studies of the caving mechanism of overburden strata have been reported.…”

“…The redistribution of the overburden stress regime caused by longwall mining brings about general increases in fracture porosity and permeability owing to the development of fractures, joints, and bedding separations, resulting in the disruption of the natural groundwater flow system to a great extent [12,15,16,44]. Currently, a variety of methods, ranging from analytical methods and field experiments to numerical and physical simulation, have been used that mainly focus on the mining-induced effects on the movement of overburden strata, the generation of fractures, and subsidence [2,13,29,30,[45][46][47]. However, very few detailed studies of the caving mechanism of overburden strata have been reported.…”

Influence of Spatial Relationships between Key Strata on the Height of Mining-Induced Fracture Zone: A Case Study of Thick Coal Seam Mining

“…Some scholars have used endoscopic observations of fractures to describe the quality of rocks, and studied the rock mass stratification [18][19][20]. Zhang et al have proposed the use of on-site radon detection to monitor the evolution of mining-induced fractures in overburden and demonstrated its feasibility through field experiments [21,22]. Applications of these detection techniques and equipment make the analysis of mining-induced CFZ's height easier and more accurate.…”

A Novel Comprehensive Detection Method for the Dynamic Characteristics of Coalface Overburden: A Case Study in China

“…Under normal circumstances, the radon collectors can be taken out from the pits for measurement four hours after placement [33]. During this on-site measurement, each radon collector was embedded in the pit for 24 h and taken out for measurement once per day [34], due to limitations in the field conditions. The coalface kept advancing during the intervals.…”