Unregulated underground group mining in China has led to problems such as unclear locations and complex shapes of mine goafs in mineral engineering, posing serious safety hazards for subsequent mining operations. This paper takes mineral engineering with complex mine goafs as the research object, integrates multi-survey data from surface deformation remote sensing monitoring and 3D laser scanning measurement to survey the area where the surface deformation rate reaches 14cm/ year, accurately identifies the location of risky mine goafs, and constructs detailed representations of the real shapes of the complex mine goafs inside the mineral engineering. The FLAC^3D 6.0 software is used to establish a 3D numerical simulation model of the mine goafs, fully considering the mining process, and conducting characteristic analysis of the stress distribution, failure range and surface deformation response of the mine goafs, revealing the impact of void deformation on the stability of the mine. The numerical simulation results are combined with on-site investigations to verify whether geological disasters have been caused by mine goafs. The research methods and results can provide effective technical means for the detailed survey and stability assessment of mineral engineering with complex mine goafs, which can help to reduce the risk of geological disasters in mines and improve the safety of mineral engineering.

The transformation of abandoned open-pit mines into pumped-storage power station reservoirs offers an effective way to optimize China’s energy structure and supports China’s dual-carbon objectives by providing large-scale flexible storage. However, the steep slopes and complex geological conditions formed by mine excavation pose severe challenges to the stability of reservoir slopes. This paper focuses on a pumped-storage power station project converted from an abandoned mine pit in Luanping, Hebei Province. Specifically addressing high and steep slopes containing weak faults, it proposes a stability analysis method for the excavation stage that considers the influence of faults. The analysis assumes dry conditions, excluding reservoir-induced pore water pressure and seepage forces. Adopting the Janbu method and the M-P method within the limit equilibrium framework, safety analyses were conducted on multiple typical analysis sections of the abandoned mine pit before and after excavation. Analytical results indicate that the minimum safety factors derived from the Janbu method pre- and post-excavation are 1.33 and 2.13, respectively, whereas those obtained via the M-P method are 1.40 and 2.47. Given its consistently lower and thus more rigorous estimations, the Janbu method is recommended for conservative engineering design and risk assessment in similar geological settings. It is found that when the fault outcrop daylighting on the slope face constitutes a substantial spatial proportion, the potential sliding surface of the slope will extend from the top of the weak fault along an arc to the bottom of the stepped excavation. This indicates that the position of the fault influences both the sliding mode and the safety performance of the slope. The research findings of this paper could provide technical support for the slope engineering design, excavation and construction of pumped-storage power station reservoirs converted from abandoned mine pits.

Distributed Acoustic Sensing (DAS) technology, characterized by its high spatial resolution, superior dynamic sensitivity, and cost efficiency, has demonstrated broad application prospects in the field of monitoring fracture development within rock masses. Nevertheless, current research regarding the application of DAS to rock crack evolution and the underlying fracture mechanisms remains to be further explored. In this study, uniaxial compression tests (UCT) were conducted on rock specimens of four different lithologies and with varying numbers of pre-existing fissures. First, a DAS monitoring system was utilized to monitor and record the entire rock fracture process in real time. To address the low signal-to-noise ratio (SNR) characteristic of DAS data, four combined denoising methods tailored for DAS signals were compared and tested. Subsequently, the rock failure process was partitioned into five distinct stages based on four key stress thresholds and the associated DAS characteristic parameters. Furthermore, by analyzing the spectral characteristics and frequency band ranges of each stage, the crack evolution and stage identification for rocks with various lithologies and fissure numbers were further elucidated. Finally, the evolution trends of tensile and shear cracks in the rock were investigated through PF-PA feature analysis. The results demonstrate that under uniaxial compression test (UCT) conditions, the DAS spectral characteristics within the 0–300 Hz frequency band can be used to effectively identify the evolution trends of mixed-mode cracks during rock fracture. This conclusion provides a valuable reference for enhancing the reliability of early warning systems for rock mass structural instability.