The Spatial Evolution Law and Water Inrush Mechanism of Mining-Induced Overburden in Shallow and Short Coal Seam Group

Abstract

In order to grasp the overburden evolution law of the shallow and short coal seam group, based on the key bed theory, a mechanical analysis of the longitudinal expansion of mining-induced overburden fractures in the coal seam group was carried out, and the spatial evolution characteristics of mining-induced overburden fractures were simulated by the numerical simulation method. The results show that in the process of working face advancement, with the continuous instability and failure of the overburden, the size and shape of the fracture network are also changed. The repeated mining of the lower coal seam further causes the secondary activation of the upper overburden, which makes the roof fractures of the partially compacted goaf violently move again. The “channel source” and “space source” continue to carry out the process of “generation-expansion-compression-generation-expansion”, in combination with pore fracture elastic theory. The water inrush characteristics of the whole coal seam are divided into three “solid-liquid” coupling stages: the original gap seepage stage, the initial water discharge stage of mining fissures and the water inrush stage of fractured rock mass. The steady value of water inflow and its variation characteristics with time are predicted by using the formula of deep well flow in a confined aquifer.

Investigating Disaster Mechanisms Triggered by Abrupt Overburden Fracture Alterations in Close-Seam Mining Beneath an Exceptionally Thick Sandstone Aquifer

“…This aquifer is marked by high water pressure, copious water content, and significant permeability. Mining closely situated seams may intensify roof deterioration, reduce the stability duration of surrounding rock pressure, and lead to water-conducting fracture heights that surpass established estimates [4][5][6][7]. A primary risk is the thick sandstone aquifer in the overlying strata, which signifies a considerable water source.…”

Mechanism of Bed Separation Water Inrush during the Mining of Extra-Thick Coal Seam under Super-Thick Sandstone Aquifer

“…China is a country with large coal resources (about 5 × 10 12 t), and its raw coal production reached 4.56 billion tons in 2022. Mine water inrush is one of the major disasters in coal mine production, and it brings heavy casualties and economic losses to coal enterprises [1][2][3]. According to statistics, in the past 30 years, more than 300 pairs of mines in China were submerged due to water inrush, and economic losses amounted to more than USD 6 billion.…”