Abstract
With the continuous increase of the upper limit of coal mining, in mining areas near unconsolidated layers, water and sand inrush disasters occur from time to time, seriously threatening the safety of mine production. In this paper, the process of water and sand inrush accidents induced by mining near unconsolidated layers is analyzed using mechanical analysis and numerical simulation methods, based on the principle of silo unloading and arching and combined with actual water and sand inrush characteristics; the critical water and sand inrush arching mechanism is explained. The paper also proposed and established three critical arching mechanics models (interlocking arch, bonded arch, and transition arch), deduced the mathematical expression of interlocking arch and transition arch, and obtained the critical instability conditions of the arch and its influencing factors. The research results have guiding significance for the occurrence of water and sand inrush disasters and the judgment of the degree of damage in mining near unconsolidated layers.
Highlights
With the reduction of mine recoverable reserves, mining shallow coal seams threatened by loose aquifers has become the preferred target for mine to extend life and potential tapping innovation
The sand mixture collapses into the underground working face, causing property losses and even death from time to time, which poses a great threat to the safety of mine production [1,2,3,4]
Sui Wanghua et al [10,11,12] proposed to use the flow behavior of particulate matter to understand the mechanism of sand break in depth and believed that the head pressure of the overlying loose aquifer and the width of the sand break channel are the key to establishing the mechanism of water and sand inrush; to increase the mining upper limit of coal seams under thick loose seams, Xu Yanchu [13, 14] studied water pressure as the key factor leading to water inrush in loose seams taking Henan Zhaogu No 1 Coal Mine as an example and revised sand-proof coal pillar formula
Summary
With the reduction of mine recoverable reserves, mining shallow coal seams threatened by loose aquifers has become the preferred target for mine to extend life and potential tapping innovation. Since the 1990s, many Chinese scholars have conducted researches on the prediction of water and sand inrush disasters and its prevention in unconsolidated layers. The aforementioned scholars studied the key factors affecting the water and sand inrush in unconsolidated layers, but there is not much research on its internal mechanism [27, 28]. Through different ratios of similar materials, simulated materials with similar physical properties of rock formations are obtained, and the internal mechanism of thick loose seams in the process of coal mining is analyzed through internal physical experiments, the law of sinking [29,30,31,32]. The judgment criterion, combined with the mathematical model to study the instability judgment law, has guiding significance for the occurrence of water and sand inrush disasters and the damage degree judgment in mining of near unconsolidated layers
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