Rock Damage Model Coupled Stress–Seepage and Its Application in Water Inrush from Faults in Coal Mines

Abstract

Mining-induced fractures often constitute water inrush channels, which lead to mine water inrush accidents. In this paper, a coupled model of stress–seepage–damage based on micromechanics is established, which simulates the initiation and propagation of cracks in rock materials and their interaction with fluid flow. The method combines the continuous damage model with the effective stress principle, in which the elastic modulus and permeability are related to the damage variables. The model is implemented via the COMSOL code based on the finite element method, and the reliability of the model is verified by the axial compression–seepage test of standard rock samples. According to the actual geological conditions of F13 fault in Wugou Coal Mine, Anhui Province, the damage of the floor rock mass and the risk of fault water inrush in the 1033 mining face with 50, 40, 30, and 20 m waterproof coal pillars are predicted. When the coal pillar width is 30 or 20 m, the fault, the surrounding rock of the fault, and the failure zone of the floor constitute the water inrush channel. This model provides an intuitive understanding of the rock damage and water inrush evolution, which is difficult to observe, and will contribute to prevent water inrush disasters in practical engineering.

Study on Water Inrush Characteristics of Hard Rock Tunnel Crossing Heterogeneous Faults

“…In recent years, with the advancement of computer technology, more and more researchers use numerical simulation methods to study the phenomenon of fault water gushing. Using FEM to discretize faults is the most common method for studying water inrush disasters [17][18][19][20]. Yang W.M., et al [21] elucidated the process of water inrush in deep tunnels by establishing a finite element model.…”

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

“…Coal is the leading energy source in China and an important industrial raw material. , Many coal mines in China have complex geological conditions; the depth of mining has been increasing in recent years, and mine water disaster seriously restricts the safe and efficient production of coal mines, − among which fault water disaster occurs in high frequencies, is highly invisible, and causes particularly severe harm. − According to statistics, more than 80% of coal floor water inrush is caused by fracture structures such as faults. − As a typical geological structure during mine production, the fault, with crack development in the coal and rock near them and damage to the native rock structure and its integrity, is very likely to become water channels between the aquifer and the coal seam under mining disturbance conditions, posing the threat of water disaster to mine production and even causing water inrush accidents, leading to economic losses and casualties . It can be seen that the fault water disaster is a severe threat to the safety of coal mine production, and it is necessary to conduct a series of studies on the fault permeability evolution and the retention of fault waterproof coal (rock) pillars.…”

“…10 − 16 As a typical geological structure during mine production, the fault, with crack development in the coal and rock near them and damage to the native rock structure and its integrity, is very likely to become water channels between the aquifer and the coal seam under mining disturbance conditions, posing the threat of water disaster to mine production and even causing water inrush accidents, leading to economic losses and casualties. 17 It can be seen that the fault water disaster is a severe threat to the safety of coal mine production, and it is necessary to conduct a series of studies on the fault permeability evolution and the retention of fault waterproof coal (rock) pillars.…”

Wettability Characteristics of Low-Rank Coals Under the Coupling Effect of High Mineralization and Surfactants

“…Experimental studies aimed at improving the wettability of coal seams and gas extraction efficiency concentrated on water injection and gas injection displacement. Research on water injection focused on the use of surfactants. − Surfactants are the main wetting agents in improving wettability, and surface tension is a key parameter for their effectiveness. − Jiang et al found that OP-10 surfactant solutions had the best effect on improving coal wettability based on surface tension and contact angle measurements of different wetting agents. , Several studies have explored the effect of wetting agents in different proportions or combined with other materials to improve the wettability of coal seams. ,− For instance, Zou et al added water-based SiO 2 nanofluids to the wetting agent solution and proposed a water injection method for coal seam improvement. , Molecular simulation software has been employed by some scholars to investigate the mechanism of surfactant effect on enhancing coal seam wettability. ,, In addition, the COMSOL simulation software was used to develop a coupled damage model during water injection to increase gas extraction rates. , Studies on gas injection displacement for improving gas extraction rates can be categorized into two types: using gases with strong adsorption capacity or gases that can break the dynamic balance of coal seam gas. − CO 2 -enhanced coalbed methane (CO 2 -ECBM) technology is essential to ensure energy security and achieve the “dual carbon” goal. This technology is crucial for achieving the low-carbon, clean, and efficient utilization of coal-based fossil energy.…”

“… 16 , 24 , 25 In addition, the COMSOL simulation software was used to develop a coupled damage model during water injection to increase gas extraction rates. 26 , 27 Studies on gas injection displacement for improving gas extraction rates can be categorized into two types: using gases with strong adsorption capacity or gases that can break the dynamic balance of coal seam gas. 28 − 30 CO 2 -enhanced coalbed methane (CO 2 -ECBM) technology is essential to ensure energy security and achieve the “dual carbon” goal.…”