This study focuses on the seismic safety of distributed underground reservoirs in coal mines, especially in scenarios involving the establishment of multiple reservoirs within the same mining area, spanning different coal seams. Dynamic similarity model tests and numerical simulations are employed to investigate the construction and operation of these reservoirs under extreme conditions, such as mine tremors or earthquakes. Utilizing the Daliuta coal mine underground reservoir as a case study, a similarity material model test platform is established to represent both upper and lower coal mine underground reservoirs. Stability tests are conducted on the interlayer rock mass under various levels of seismic intensity, and the safety of the interlayer rock mass at different safety distances is comparatively analyzed. Meanwhile, using the finite element method, the responses of the upper and lower coal mine underground reservoirs under different seismic intensity levels are simulated with the same conditions of model tests. Through the two types of simulations, the mechanical response and safety of the surrounding rock of the Daliuta coal mine underground reservoir under the influence of different seismic intensities are systematically analyzed, and the reasonable safety distances between the upper and lower reservoirs are obtained. This study provides a valuable scientific insight into the safe design of underground reservoir embankments in coal mines.

Coal mining is often associated with groundwater pollution and loss, and coal–water conflicts are becoming increasingly prominent in Western China. As a new way to protect mine water, coal mine underground reservoirs (CMURs) have effectively alleviated the water shortage problem in Western China. The CMURs have been in existence for 25 years, but field-monitoring studies on their long-term stability are rare. In this paper, we take the Shigetai coal mine in the Shendong mining area as the research background. Long-term observation of stress, deformation, seepage pressure, and other parameters of 22 dams in five goaves (31201–31205) of the Shigetai coal mine for the whole year of 2022 has been pioneeringly carried out. A novel early-warning model, which incorporates expert evaluations and real-time indicator fluctuations, is proposed to assess the stability of CMURs. The stability characteristics of coal pillar dams (CPDs) and artificial dams (ADs) of CMURs are evaluated by this model, proving the validity and applicability of this model. This model provides theoretical and methodological guidance for long-term monitoring and early-warning systems for CMURs in the Shendong mining area.

This study conducted uniaxial creep tests on coal samples under both natural and water-saturated conditions for durations of about 180 days per sample to study the stability of coal pillar dams of the Daliuta Coal Mine underground reservoir. Combined with synchronized acoustic emission (AE) monitoring, the research systematically revealed the time-dependent deformation mechanisms and damage evolution laws of coal under prolonged water immersion and natural conditions. The results indicate that water-immersed coal exhibits a unique negative creep phenomenon at the initial stage, with the strain rate down to −0.00086%/d, attributed to non-uniform pore compaction and elastic rebound effects. During the steady-state creep phase, the creep rates under water-immersed and natural conditions were comparable. However, water immersion led to an 11.4% attenuation in elastic modulus, decreasing from 2300 MPa to 2037 MPa. Water immersion would also suppress AE activity, leading to the average daily AE events of 128, which is only 25% of that under natural conditions. In the accelerating creep stage, the AE event rate surged abruptly, validating its potential as an early warning indicator for coal pillar instability. Based on the identified long-term strength of the coal sample, it is recommended to maintain operational loads below the threshold of 9 MPa. This research provides crucial theoretical foundations and experimental data for optimizing the design and safety monitoring of coal pillar dams in CMURs.

Conventional bolts frequently fail under large deformations due to stress concentration in soft rock tunnels. In contrast, yielding bolts incorporate energy-absorbing mechanisms to sustain controlled plastic deformation. This study employed FLAC3D to numerically investigate the pull-out, shear, and bending behaviors of yielding bolts, evaluating their support effectiveness in soft rock tunnels. Three-dimensional finite difference models incorporating nonlinear coupling springs and the Mohr–Coulomb criterion were developed to simulate bolt–rock interactions under multifactorial loading. Validation against experimental pull-out tests and field measurements confirmed the model accuracy. Under pull-out loading, the axial forces in yielding bolts decreased more rapidly along the bolt length, reducing stress concentration at the head. The central position of the maximum load-bearing capacity in conventional bolts fractured under tension, resulting in an hourglass-shaped axial force distribution. Conversely, the yielding bolts maintained yield strength for an extended period after reaching it, exhibiting a spindle-shaped axial force distribution. Parametric analyses reveal that bolt spacing exerts a greater influence on support effectiveness than length. This study bridges critical gaps in understanding yielding bolt behavior under combined loading and provides a validated framework for optimizing energy-absorbing support systems in soft rock tunnels.

Accurate, comprehensive, and spatially continuous monitoring of mining-induced surface subsidence is essential for geohazard prevention, ecological restoration, and safe mining. Conventional approaches, however, are limited by the sparse spatial distribution of GNSS observations, the difficulty of InSAR in resolving large and rapidly evolving deformation, and the reliance of probability integral method (PIM) calibration on sparse observations. Here, we evaluate an integrated UAV-LiDAR–PIM workflow for basin-wide characterization of mining-induced subsidence and improved spatial constraint of PIM parameters. We use the 3206 working face in an Ordos mining area as a case study. DEM differencing of multi-temporal UAV-LiDAR observations characterizes the spatial distribution of the subsidence basin. Uniform sampling within the affected zone then provides a high-density dataset for PIM calibration, which we compare with conventional profile-based monitoring. The two UAV-LiDAR DEM epochs yielded vertical quality-control RMSEs of 0.052 and 0.050 m, respectively, with a mean of 0.051 m. These results support their use for basin-scale deformation analysis. The inverted angular parameters indicate a larger mining influence extent along the dip direction than along the strike. Surface movement followed initial, active, and declining stages over 423 days, with a maximum subsidence rate of 87.39 mm d⁻¹ during the active stage. The integrated workflow reduces the spatial-sampling limitations of profile-based monitoring and adds two-dimensional constraints on basin geometry and directional variation. Combining basin-wide UAV-LiDAR observations with conventional profiles may improve site-specific PIM calibration and support mining-hazard assessment and ecological-restoration planning.

Underground coal mine reservoirs experience repeated impoundment and drainage, exposing coal pillars to dry–wet cycling and causing cumulative deterioration. This study investigated the acoustic and mechanical responses of Wudong coal specimens subjected to 0, 1, 3, and 5 dry–wet cycles through mass measurements, P-wave velocity (Vp) tests, and uniaxial compression. The results show that dry mass, saturated water content, and Vp evolve nonlinearly with increasing cycle number, suggesting staged pore–crack rearrangement and water–coal interaction. A pronounced acoustic response occurs around the third to fourth cycle, while saturated-state Vp is more sensitive than dry-state Vp because of water filling, mineral swelling, and changes in local acoustic impedance. The uniaxial compressive strength and elastic modulus decrease by up to 49.7% and 28.4%, respectively, after three cycles. Meanwhile, the failure mode changes from shear-dominated failure to tensile–shear and tensile–compressive hybrid failure. The deterioration is mainly attributed to water adsorption, clay-mineral swelling, dissolution and migration of fine particles, and pore redistribution. These findings indicate that Vp, combined with mass and mechanical parameters, can provide a useful basis for evaluating moisture-induced damage in coal pillars of underground coal mine reservoirs.