Impact of Mine Panel Size on Hydraulic Permeability of Weakly Cemented Strata

Abstract

The effect of underground coal mining on groundwater, ranging from minimal to severe depending on the mined-out panel size, is primarily associated with the change in ground hydraulic permeability. This paper presents a novel panel design method, taking consideration of reducing water loss during the mining operation, which is based on evaluating and ranking the impact of panel size on the hydraulic permeability of weakly cemented strata. The permeability test results of weakly cemented rock samples collected in the Yili No.4 Coal Mine in Xinjiang, China strongly indicates that, in contrast to common rock, their post-peak permeability during the total stress-strain process is lower than the initial permeability due to high porosity and the presence of clay minerals. A numerical modeling based on strain-permeability functions reveals that the post-mining permeability distribution in the weakly cemented overlying strata could be subdivided into three zones: the permeability reduction zone, the permeability restoring zone, and the permeability high-increment zone. The impact significance of different size factors on the post-mining permeability of overlying strata can be ranked in decreasing order as follows: mining height, panel width, and panel length, the quantification of which was based on the variance analysis of such indices as maximum pore pressure and maximum flow velocity. Based on the above findings, the optimal size of panel 21103 in the Yili No.4 Coal Mine was determined and validated by water level field observations.

Fracture Propagation and Hydraulic Properties of a Coal Floor Subjected to Thick-Seam Longwalling above a Highly Confined Aquifer

“…conducted an experimental study on the permeability of weakly cemented sandstone and obtained the relationship between volumetric strain and permeability of weakly cemented rocks [19]. Similarly, Yu et al [30] studied the permeability property of rock samples along different stress paths and obtained a curve of sandstone.…”

“…In this context, mining parameters are critical factors contributing to floor permeability enhancement. In fact, research achievements in this field are limited, and most of them are associated with the overburden rather than floor rocks [19][20][21]. For example, Khanal et al [22] studied how different geometries of the longwall panel affect the permeability of overburden strata by means of numerical modelling and obtained the corresponding variation law of permeability.…”

Study of the Influence of Clay Minerals on the Mechanical and Percolation Properties of Weakly Cemented Rocks

“…Weakly cemented rock has the characteristics of deterioration in water. Some scholars have studied the seepage characteristics of weakly cemented rock [37][38][39][40][41][42]. Guo et al created a theoretical model and mathematical relationships to describe the weakening of rock modulus and strength induced by water absorption in the rock substrate.…”

Aquiclude Stability Evaluation and Significance Analysis of Influencing Factors of Close-Distance Coal Seams: A Case Study of the Yili No. 4 Coal Mine in Xinjiang, China

“…They provided no quantitative assessment of the aquiclude stability or considered the seepage effect. In coal-bearing strata of western China, which have a short diagenesis time, aquicludes are rich in clay minerals, such as montmorillonite, illite, and kaolin, and are prone to swelling and sealing fractures when exposed to water [27,28]. As a result, such aquicludes are not necessarily completely destabilized after cracks are generated, or the deformation reaches the limit value.…”