Study on the Evolution of Fault Permeability and the Retention of Coal (Rock) Pillar under the Mining Conditions of Thick Coal Seam in the Footwall of Large Normal Fault

Abstract

As a typical geological structure, the fault often threatens the safe mining of coal mines. In order to investigate the permeability evolution of the significant normal fault under the mining disturbance of the thick coal seam of the fault footwall and to propose a scientific and reasonable coal (rock) pillar retention plan, this paper took the YinJiaWa Fault (YJW Fa), a large normal fault, in Fucun Coal Mine, Shandong Province, China, as a research object, conducted a coupled fluid and solid simulation study on permeability evolution of the fault using COMSOL Multiphysics, based on the revealed geological data and rock mechanical parameters, and combined the theoretical calculation results to determine the width of the waterproof coal (rock) pillar. The results show that the width of the waterproof coal (rock) pillar of YJW Fa is negatively correlated with the porosity, permeability, and flow velocity of each monitoring point. With the width of 60 m as the dividing point, as the width left less than 60 m and gradually reduced to 30 m, its water-blocking capacity is destroyed, increasing the seepage velocity in the water-flowing fractured zone, forming a water channel, causing water inrush accidents. The formula and numerical simulation results are used to determine the width of the waterproof coal (rock) pillar of the YJW Fa to be 74.44−84.08 m, to ensure the safe mining of the fault footwall. This paper provides a theoretical basis for further understanding of the fault permeability development rules and safety guidance for coal seam mining of the fault footwall.

Research on the Law of Coal Pillar Spontaneous Combustion and Fire Prevention and Control Technology

“…In the treatment of mine fire, techniques such as yellow mud injection, inert gas injection, and loess covering are generally adopted. − With the development of science and technology, mine fire prevention and control technology continue to progress. Such as three-phase foam as the representative of the foam class fire prevention materials, as well as the colloid as the representative of the colloid fire prevention materials gradually into the field of vision, the field application effect is remarkable. , Regarding research on coal pillars, most scholars at home and abroad focus on the mechanical characteristics and fragmentation mechanism of coal pillars. − However, it is worth noting that coal pillar cracks, under the influence of underground formation pressure, would further develop and result in a large number of air leakage channels. Besides, air circulation caused by the atmospheric pressure difference on both sides of coal pillars may also accelerate the spontaneous combustion of fragmented coal in coal pillars. , Under the guidance of safety-related coefficient criteria and safety principles, Tang divided the narrow coal pillar and the goaf into “safe zone”, “general zone”, and “dangerous zone”, according to two indicators, i.e., the permeability of the narrow coal pillar and the spontaneous combustion risk of residual coal in the goaf .…”

Study on the water conductivity of large-scale boundary fault of the mine field and the design of water-proof coal pillar

“…Against the backdrop of the current trend in North-China-type coalfields towards deep-mining production (Xie 2017;Guo & Luo 2022), these types of faults often serve as crucial conduits linking the aquifers in the Taiyuan Formation limestone and the Ordovician limestone. To ensure the safe excavation of coal seams at field boundary, it is generally necessary to retain appropriately sized fault-controlled water-proof coal pillar (Yin et al 2023).…”

Determination of Critical Damage Size of Inclined Waterproof Coal Pillar under Asymmetric Load

“…The analysis of the influence of the overburden collapse process and the development characteristics of the water-conducting fracture zone on the stability of the waterproof pillar is given using a physically similar simulation [30][31][32][33][34][35]. In recent years, with the widespread development of computers, numerical simulation has gradually become a new means to study the size of waterproof coal pillars [36][37][38][39][40]. Many scholars mostly use the seepage and deformation theory to establish the numerical model of solid-flow coupling in the coal seam mining process to reveal the stress evolution law of coal pillars of different widths under the influence of water and mining, which is used as the basis for the size of waterproof pillars [41][42][43].…”