Abstract
The overburden rock mining fissures are the main cause of coal spontaneous combustion, gas pooling, and mine water inrush caused by goaf air leakage. Rapid and accurate determination of the development and evolution law of mining fissures have great significance for the application of coal spontaneous combustion prevention and control, gas disaster prevention and control, and water damage prevention and control measures. In this paper, a preliminary judgment of the development height of the water-conducting fracture zone is made based on the theoretical analysis, and the physical model size of the numerical simulation is determined according to its judgment result. It is judged that the development height of its water-conducting fracture zone is between 49 and 64.2 m, which is in line with the actual results. Based on this, a three-dimensional solid model was established in PFC (Particle Flow Code) software to analyze the fissure development pattern of the overburden rock and the development height of the water-conducting fracture zone when the main key stratum of the rock seam is in different positions by simulating the excavation process of the coal seam. The results show that when the main key stratum is located in the “original crack belt boundary,” the development of water-conducting fracture zone is significantly inhibited; when the main key stratum is located in the “original caving zone,” the water-conducting fracture zone is fully developed, and the crack belt finally develops to the top of the model. In order to verify the accuracy of the numerical simulation, similar material simulation experiments were performed under the same scheme. The results are consistent with the numerical simulation conclusions, effectively verifying the accuracy of the numerical simulation. Finally, the extraction of porosity of the goaf was carried out based on numerical simulation, and the permeability zoning of the goaf was performed; the results show that the development of the water-conducting fracture zone has a significant influence on the permeability of the mining area, and the more fully developed the fissure is, the greater is its permeability. In this paper, the fissure development law in the goaf under different key stratums is explored by various research stratums, and the results show a good consistency, which provides a scientific basis for the prevention and control of disasters such as water inrush and coal and gas outburst in mines, and provides theoretical guidance for safe mining.
Highlights
As shallow coal seam is mined out and shallow coal resources are gradually depleted, deep mining will become the new normal for coal resource mining in China [1]
In this paper, using the 7435 working face of the Kongzhuang coal mine as a prototype, the transport and breaking law of overlying strata under different key strata were explored by means of theoretical analysis, and similar material simulation experiments, numerical simulation, and the development height of its waterconducting fracture zone was predicted and judged
On the basis of numerical simulation, the porosity values were extracted and the permeability zoning of the goaf was classified by its results. e main conclusions obtained are as follows: (1) Based on the theoretical analysis, a preliminary judgment was made on the development height of the water-conducting fracture zone
Summary
As shallow coal seam is mined out and shallow coal resources are gradually depleted, deep mining will become the new normal for coal resource mining in China [1]. E location of the key stratum has a significant influence on the development of mining fissures, and many scholars have conducted a lot of empirical and theoretical studies on coal mining overburden rock damage and the height of mining overburden rock fissure development. Liu et al [25] used physical and numerical simulations to study the effect of the presence of key stratum on the movement of overburden rock at the fully mechanized mining workface, and the results showed that the presence of overburden key stratum is crucial for coal mining, especially for the upper section of a single key stratum. Li et al [27] used UDEC numerical simulation software to analyze the effect of the breakage of the compound key stratum on the overburden rock and ground pressure, and the results showed that the inferior key stratums affected by mining all exhibited sliding instability and could not form a stable body-beam structure after the breakage and collapse. On the basis of numerical simulation, the porosity between the rock formation and the goaf is derived, and the permeability zoning is carried out according to the porosity to guide the key prevention area of mine water inrush, in order to achieve the effect of preventing and controlling water inrush
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