Abstract
Underground coal mining inevitably causes ground fissures, especially permanent cracks that cannot be closed at the boundary of the working face. Studying the underground three-dimensional morphology of the permanent cracks allows one to accurately constrain the formation and development of the ground fissures. This information will contribute to reducing mine disasters and is also a prerequisites to avoid environmental pollution. We selected the Zhangjiamao coal mine (China), which is situated in a collapsible loess area, as a case study for deciphering the formation of permanent cracks. After injecting gypsum slurry into the mine, a three-dimensional model of the ground fissures is obtained by three-dimensional (3D) laser scanner technology that records the 3D underground morphology. Integrating the geological context of a collapsible loess area, the characteristics and main processes of the ground fissure development are constrained: (1) The width of the ground fissure decreases to 0 with increasing depth and is strongly affected by the soil composition. (2) Along the vertical extension direction, the ground fissures are generally inclined to the inner-side of the working face, but the direction remains uncertain at different depths. (3) The transverse propagation direction of the ground fissure becomes more complex with increasing depth. (4) Under the influence of soil texture and water, loose soil fills the bottom of the ground fissure, thus affecting the underground 3D morphology.
Highlights
Introduction iationsCoal is currently still the main energy source in China [1]
The article is structured as follows: In the section “Materials and Methods”, we describe the sample material, the experimental set-up, and the data acquisition that leads to the constructing of a 3D model of the ground fissure
“Discussion” we introduce the complexity of the underground morphology of the ground fissure, the rationality of our experimental results, and the deficiencies of the experimental methods, along with suggestions for improvement
Summary
Introduction iationsCoal is currently still the main energy source in China [1]. According to BP’s StatisticalReview of World Energy 2020, the world’s coal mining volume was 7.742 billion tons.China’s coal mining volume of 3.902 billion tons accounts for ca. 50% of the world’s volume. Review of World Energy 2020, the world’s coal mining volume was 7.742 billion tons. China’s coal mining volume of 3.902 billion tons accounts for ca. In China’s energy structure, coal resources still account for 57% [2]. Ground fissures are widely distributed among the surface damage, causing many, often long-lasting, problems and disasters [6]. This may cause the reduction of the soil quality and the contamination of water resources and may weaken the structures and stability of buildings [7,8,9,10,11,12,13].
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