Study on Coupled Evolution Mechanisms of Stress–Fracture–Seepage Fields in Overburden Strata During Fully Mechanized Coal Mining
Abstract
:1. Introduction
2. Experimental Study on Permeability of Coal Rock Sample in Different Overburden Strata Zoning
2.1. Overburden Strata Zoning
2.2. Permeability Model
2.3. Experimental Program
- (1)
- Raw coal rock samples (Figure 3a): The original coal samples and original rock style samples were chosen, and the larger, better integrity, un-weathered coal rock blocks in the coal mining face and overburden strata were directly selected. In the laboratory, according to the ‘coal and rock physical and mechanical properties determination method’, the provisions were processed into standard raw coal samples, at a size of ϕ50 mm × 100 mm.
- (2)
- Fracture coal rock samples (Figure 3b): The standard coal rock samples were processed into sizes of ϕ50 mm × 100 mm and were subjected to a shear test; after the shear damage occurred, the coal samples in which both halves had more complete shear damage were selected for further processing. After the shear damage, the coal sample was generally divided into two halves, and the integrity of each half of the coal rock sample was better, while the penetrating fractures were perpendicular to the two ends of the sample.
- (3)
3. Coupled Simulation of Mining Stress–Fracture–Seepage Fields
3.1. Construction of a Coupled Fluid–Solid Simulation Method
3.1.1. FLAC3D Fluid Structure Coupling Calculation Method
- (1)
- Seepage calculation method
- (2)
- Mechanical calculation methods
3.1.2. Module for Updating the Permeability Dynamics of Coal Rock Bodies
3.1.3. A Coupled Simulation Method of Mining Stress–Fracture–Seepage Fields
- (1)
- Coal rock zoning and permeability modeling
- (2)
- Permeability dynamic updating mechanism
- (3)
- Multi-field coupled numerical simulation flow (Figure 5)
3.2. Engineering Background
3.3. Numerical Model and Parameters
3.3.1. Model Construction
3.3.2. Parameter Selection
3.3.3. Measuring Point Arrangement
4. Seepage Evolution Mechanisms of the Mining-Disturbed Overburden Aquifer
4.1. Characteristics of Overburden Permeability Mining Evolution
4.2. Seepage Migration Characteristics of Overburden Aquifer
5. Conclusions
- (1)
- This study systematically investigated the coupled evolution mechanisms of stress–fracture–seepage fields in overburden strata through integrated experimental and numerical approaches. Laboratory triaxial permeability tests on three types of damaged coal rock samples (raw, fractured, and broken) revealed distinct seepage behaviors: fractured samples exhibited 23–48 times higher initial permeability (28.03 mD for coal, 13.54 mD for rock) compared to intact samples, while broken rock permeability decayed exponentially from 120.32 mD to 23.72 mD under compaction. These findings established quantitative permeability models (R2 > 0.99) that effectively characterize zonal differences in mining-induced damage, providing a critical experimental basis for multi-field coupling simulations.
- (2)
- A dynamic coupling methodology was developed by integrating FISH scripting with FLAC3D, enabling real-time permeability updates based on stress states and failure zone identification. The algorithm embedded three mechanisms: stress-dependent exponential decay for intact zones, yield-triggered permeability jumps for fractured regions, and compaction-driven nonlinear evolution for caved zones. This approach bridged the gap between static laboratory models and dynamic mining conditions, achieving automatic multi-field coupling during face advancement simulations.
- (3)
- Numerical simulations of the Luotuoshan 110,901 working face identified critical seepage thresholds and spatial patterns. High-permeability zones (5–15 × background values) persistently localized at goaf boundaries and fracture zones, with peak permeability (81.67 mD) occurring at 200 m advancement. The simulated fracture zone height reached 55 m, directly connecting with the overlying aquifer (9 m thick, 1 MPa pressure), consistent with field-measured water inrush events. These results demonstrated the method’s capability to predict water-conducting fracture development and optimize drainage strategies.
- (4)
- The stress–fracture–seepage coupling process evolved through four quantifiable stages: static equilibrium (0–100 m, <5 mD), fracture expansion (120–200 m, +484% permeability), seepage channel formation (200–300 m, aquifer connectivity), and high-risk inrush (300–400 m, 23.72 mD stabilized flow). These findings provide actionable thresholds for staged prevention measures—grouting before 200 m, targeted dewatering at 260–320 m, and enhanced drainage beyond 340 m. The methodology offers a predictive framework for deep mining water hazards, with future research recommended for multi-aquifer systems and real-time monitoring integration.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Type of Sample | Fitting Parameter | Correlation Coefficient R2 | |||
---|---|---|---|---|---|
kw (mD) | cw0 (MPa−1) | αw (MPa−1) | cw0/αw | ||
Raw coal sample | 0.5034 | 0.3020 | 0.1105 | 2.7330 | 0.9993 |
Raw rock sample | 0.2133 | 0.3450 | 0.1247 | 2.7667 | 0.9993 |
Fracture coal sample | 28.0314 | 0.1310 | 0.1056 | 1.2405 | 0.9990 |
Fracture rock sample | 13.5438 | 0.1104 | 0.1364 | 0.8094 | 0.9980 |
Broken rock sample | 120.3242 | 0.0303 | 0.2523 | 0.1201 | 0.9930 |
Type of Coal Sample | Fitting Formula | Formula Number |
---|---|---|
Raw coal sample | RC | |
Raw rock sample | RR | |
Fracture coal sample | FC | |
Fracture rock sample | FR | |
Broken rock sample | BR |
Numbering | Lithology | Thickness/m | Density/kg·m−3 | Bulk Modulus /GPa | Shear Modulus/GPa | Cohesion /MPa | Angle of Internal Friction/° | Tensile Strength/MPa |
---|---|---|---|---|---|---|---|---|
1 | Fine sandstone | 24 | 2500 | 1.5 | 1.4 | 0.8 | 22 | 0.9 |
2 | Mudstone | 7 | 2000 | 1.0 | 1.0 | 0.5 | 20 | 0.5 |
3 | Fine sandstone | 10 | 2500 | 1.5 | 1.4 | 0.8 | 22 | 0.9 |
4 | Mudstone | 12 | 2000 | 1.0 | 1.0 | 0.5 | 20 | 0.5 |
5 | Fine sandstone–aquifer | 9 | 1400 | 2.5 | 2.3 | 2.5 | 16 | 1.5 |
6 | Fine sandstone | 7 | 2500 | 1.5 | 1.4 | 0.8 | 22 | 0.9 |
7 | Mudstone | 6 | 2000 | 1.0 | 1.0 | 0.5 | 20 | 0.5 |
8 | Siltstone | 2 | 2500 | 1.5 | 1.4 | 0.8 | 22 | 0.9 |
9 | Mudstone | 10 | 2000 | 1.0 | 1.0 | 0.5 | 20 | 0.5 |
10 | Mudstone | 6 | 2000 | 1.0 | 1.0 | 0.5 | 20 | 0.5 |
11 | Fine sandstone | 7 | 1800 | 1.5 | 1.5 | 1.2 | 18 | 1.2 |
12 | Mudstone | 10 | 2000 | 1.0 | 1.0 | 0.5 | 20 | 0.5 |
13 | Siltstone | 2 | 2500 | 1.5 | 1.4 | 0.8 | 22 | 0.9 |
14 | Mudstone | 5 | 2000 | 1.0 | 1.0 | 0.5 | 20 | 0.5 |
15 | Coal 9# | 7 | 1400 | 2.5 | 2.3 | 2.5 | 16 | 1.5 |
16 | Mudstone | 1 | 2000 | 1.0 | 1.0 | 0.5 | 20 | 0.5 |
17 | Coal 10# | 1 | 1400 | 2.5 | 2.3 | 2.5 | 16 | 1.5 |
18 | Mudstone | 6 | 2000 | 1.0 | 1.0 | 0.5 | 20 | 0.5 |
19 | Siltstone | 2 | 2500 | 1.5 | 1.4 | 0.8 | 22 | 0.9 |
20 | Mudstone | 8 | 2000 | 1.0 | 1.0 | 0.5 | 20 | 0.5 |
21 | Fine sandstone | 4 | 2500 | 1.5 | 1.4 | 0.8 | 22 | 0.9 |
22 | Mudstone | 24 | 2000 | 1.0 | 1.0 | 0.5 | 20 | 0.5 |
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Liu, Y.; Fang, S.; Hu, T.; Zhang, C.; Guo, Y.; Li, F.; Huang, J. Study on Coupled Evolution Mechanisms of Stress–Fracture–Seepage Fields in Overburden Strata During Fully Mechanized Coal Mining. Processes 2025, 13, 1753. https://doi.org/10.3390/pr13061753
Liu Y, Fang S, Hu T, Zhang C, Guo Y, Li F, Huang J. Study on Coupled Evolution Mechanisms of Stress–Fracture–Seepage Fields in Overburden Strata During Fully Mechanized Coal Mining. Processes. 2025; 13(6):1753. https://doi.org/10.3390/pr13061753
Chicago/Turabian StyleLiu, Yan, Shangxin Fang, Tengfei Hu, Cun Zhang, Yuan Guo, Fuzhong Li, and Jiawei Huang. 2025. "Study on Coupled Evolution Mechanisms of Stress–Fracture–Seepage Fields in Overburden Strata During Fully Mechanized Coal Mining" Processes 13, no. 6: 1753. https://doi.org/10.3390/pr13061753
APA StyleLiu, Y., Fang, S., Hu, T., Zhang, C., Guo, Y., Li, F., & Huang, J. (2025). Study on Coupled Evolution Mechanisms of Stress–Fracture–Seepage Fields in Overburden Strata During Fully Mechanized Coal Mining. Processes, 13(6), 1753. https://doi.org/10.3390/pr13061753