Jiangzhan Chen

Reliable assessment of rockburst tendency is essential for maintaining the stability and operational safety of deep underground excavations. However, the complex coupling among stress conditions, lithological characteristics, and structural features of rock masses introduces significant uncertainty into rockburst prediction. Conventional evaluation approaches relying on individual indices frequently produce inconsistent classifications and are often insufficient to represent actual rockburst behavior. To address this issue, a hybrid evaluation framework integrating unascertained measure theory, cloud-based uncertainty analysis, and a game-theoretic weighting strategy was developed in this study. Four representative parameters, including the strain energy storage index (W_et), geostress index (S), rock quality designation (RQD), and rock mass integrity factor (K_v), were adopted to characterize the energy-storage capability, stress environment, and structural condition of the surrounding rock mass. The conventional unascertained measure approach was further enhanced using the normal cloud model to describe the uncertain mapping relationship between quantitative measurements and qualitative rockburst classifications. In addition, a combination weighting scheme incorporating AHP, entropy weight (EW), and CRITIC methods was established to improve the stability and rationality of index weighting. The developed framework was subsequently applied to a deep phosphate mine in China. The calculated comprehensive weights of the four evaluation parameters were 0.1982, 0.3446, 0.2173, and 0.2399, respectively, demonstrating that the stress-related parameter has the greatest influence on rockburst evaluation. The results indicate that the investigated rock masses generally exhibit moderate-to-strong rockburst tendency. The shallow and moderately deep zones exhibited relatively high rockburst potential, while the ultra-deep dolomite formations mainly showed a moderate tendency due to the development of joints and fractures, which weakened the integrity of the deep rock mass. The proposed framework provides an effective and practical approach for preliminary hazard assessment, rockburst risk zoning, and prevention strategy design in deep mining engineering.

Rock–fill composite slopes formed during the transition from underground to open-pit mining in metal mines are highly susceptible to interface hydraulic weakening and sudden sliding under intense rainfall, mainly due to the permeability contrast between the two media. Taking the Shizhuyuan Mine as a case study, a coupled hydro-mechanical numerical model was developed in ABAQUS 2025 to investigate slope stability under different rainfall patterns and interface strength degradation scenarios. The spatiotemporal evolution of seepage and deformation fields was examined in detail, with particular attention given to the variation of the safety factor, the distribution of pore water pressure along the interface, and the characteristics of interface slip. The results show that: (1) the deterioration of the hydraulic condition within the slope is governed by the water-blocking effect of the interface and the infiltration threshold of the surface layer. Under the same total rainfall, prolonged low-intensity rainfall is more likely than short-duration intense rainfall to produce sustained deep infiltration, and the factor of safety decreases from the initial 1.369 to 1.173 (0.005 m/h, 288 h) and 1.255 (0.02 m/h, 72 h), respectively, indicating that the former exerts a more pronounced weakening effect on slope stability. (2) Slope instability exhibits a clear interface-controlled pattern. Regardless of the degree of parameter degradation, the base of the plastic zone consistently develops along the rock–fill interface, accompanied by extensive plastic deformation within the overlying fill material. (3) Failure initiates at the slope toe where the mechanical equilibrium along the rock–fill interface is first disturbed. Under the combined influence of topographic conditions and the water-blocking effect of the interface, rainfall infiltration tends to converge toward the slope toe and form a local high-pore-pressure zone, resulting in a marked reduction in the effective normal stress at the interface. Once the local shear stress exceeds the shear strength, yielding is triggered first at the slope–toe interface, which then induces plastic deformation in the overlying fill material and ultimately leads to overall slope instability.

针对以光卤石为代表的盐岩矿柱在持续荷载下易发生蠕变变形的问题，开展了相似材料的研制。结合光卤石的物理力学特征以及蠕变特性，采用骨料蠕滑石蜡镀膜方法，设计了12组配比方案，基于井下矿柱实际承载情况，测试了相似材料力学和蠕变性能。试验结果表明：蠕滑石蜡镀膜骨料引入后，砂膏比与胶骨比对光卤石相似材料的物理力学性能有明显的调节作用。当镀膜骨料质量比为0.23（对应的砂膏比为2，胶骨比为0.56）时，该相似材料的基础力学性能与光卤石最为相近，且其在初始蠕变及稳态蠕变阶段的表现与光卤石的蠕变曲线较为相似。研究结果可以为相似背景矿岩相似材料的制备提供参考。

To explore the mechanism of water inrush from the mine roof strata, a series of seepage-acoustic emission (SAE) experiments on red sandstone disc samples were carried out. The effects of the height to diameter ratio (H/D) and pore pressure on the mechanical, hydraulic and crack propagation properties of red sandstones were investigated. Test results show that, the peak load of rock samples declines with the decreasing H/D and increasing pore pressure. The seepage process can be divided into three phases, i.e., lower permeability stage, and permeability fluctuation stage and high permeability stage. The crack propagation mainly appears near and after the peak load. In addition, in the low permeability stage, fluid mainly flows through the pores of rock. With the deformation and crack propagation, the fluid enters the cracks, causing fluctuations in permeability. When penetrating cracks forms, a large amount of fluid passes through the cracks, causing a rapid increase in permeability. In the case of high H/D, the water inrush phenomenon obviously lags behind the rock failure, and this lagging phenomenon becomes more significant as the water pressure decreases. The critical displacement (the displacement corresponding to the time of water inrush) can be used to characterize the risk of water inrush. The lower the H/D, the greater the water pressure and the higher water inrush risk. Therefore, it is necessary to control the distance from the working face to the overburden aquifer and reduce the groundwater pressure, so as to reduce the risk of water inrush from the roof.

Deep borehole cores are an important material basis for understanding deep stress conditions and rockburst risk; however, the complex environment of deep boreholes poses many challenges to traditional core orientation techniques, thus limiting the application of cores in fields such as in situ stress measurement. A technical method of restoring the original spatial attitude of nonoriented geological cores on the ground was proposed based on the inherent “trajectory projection consistency” relationship between the borehole and the corresponding core. A prototype machine of core ground reorientation was developed. Using this method and machine, ground reorientation was performed on cores drilled from the deepest shaft in China. Subsequently, the reoriented core acoustic emission (AE) method was conducted to identify the in situ stress within the project area. Meanwhile, measurement accuracy was verified by the stress relief method. The results show that the in situ stress distributions, including the azimuth and the trends in principal stresses by the two methods, are in good agreement and indicate that the historical maximum principal stress in the case of the mine has little abrupt variability with that of the present day. The research results can be used as the design basis for the safe construction of the deepest shaft.