实验技术与管理

为解决贵州磷矿红页岩巷道变形严重、支护成本高的问题，文章通过制备层理角度为0°、30°、45°、60°、90°的试件，采用加载速率0.1 mm/min的巴西劈裂实验，结合声发射RA(rise angle)-AF(average frequency)值的破裂判据，研究其抗拉强度与破裂模式的各向异性特征。实验发现红页岩抗拉强度随层理角增大呈递减趋势，从0°时的6.20 MPa降至90°时的3.17 MPa，降幅达48.9%;0°与90°的试件以张拉破裂（RA<3μs/d B）为主，层理角度为30°～60°的试件剪切破裂占比递增，至层理角度为45°时达75%；声发射振铃计数呈现“稳定累积—突增释放—耗散平稳”三阶段演化特征，且与应力曲线高度耦合。据此，文章提出了层理导向支护方案：层理角度为0°的巷道采用Φ22 mm的高强锚索（预应力≥150 kN），而层理角度为30°～60°的巷道则采用注浆加固层理面。该研究成果可为深部红页岩巷道控制提供依据。

[Objective] A critical issue with red shale roadways has been identified in Guizhou phosphate mines. Over 70% of roadways pass through red shale, with a 34% roof collapse rate and 5 200 yuan/m support cost. The deep red shale surrounding rock is particularly susceptible to high ground stress and dynamic disturbances(excavation, blasting), which can worsen its instability. Existing studies confirm the bedding effect of red shale, however, its correlation with the angle-fracture mode remains ambiguous. Conventional methodologies prove ineffective in capturing real-time microfractures, and the application of the acoustic emission(AE) rise angle–average frequency(RA–AF) criterion remains underdeveloped. This study explores the tensile properties, fracture mechanisms, and AE characteristics of red shale under different bedding angles to optimize roadway support. [Methods] Red shale from Guizhou phosphate mines was processed into specimens measuring Φ50 mm × 30 mm and characterized by 0°, 30°, 45°, 60°, and 90° bedding angles. The specimens were dried at 115 ℃ for 24 h and subsequently sealed to avoid moisture. An MTS81 electro-hydraulic servo machine with a loading rate of 0.1 mm/min and a PAC PCI-2 AE system were utilized in the experimental setup. Two AE probes(AB-glued) were utilized to monitor signals, with key parameters including ringing count, energy, RA, and AF. The RA–AF criterion(RA = 3 μs·d B^–1 threshold) was employed to distinguish between tensile and shear fractures, with stress–AE curve coupling analyzed. [Results] The tensile strength of red shale decreased significantly as the bedding angle increased, dropping from 6.20 MPa at 0° to 3.71 MPa at 30°, 3.43 MPa at 45°, 3.30 MPa at 60°, and finally to 3.17 MPa at 90°, representing a total reduction of 48.9%. The fracture mode of red shale also showed a clear transformation law. Specimens with 0° and 90° bedding angles(RA values of 1.2 μs·d B^–1 and 2.1 μs·d B^–1, respectively) exhibited primarily tensile failure. Specimens with 30°–60° bedding angles(RA values ranging from 18.5 μs·d B^–1 to 32.7 μs·d B^–1) exhibited an increasing proportion of shear failure, with 45° identified as the critical bedding angle at which shear failure accounted for 75%. The AE signals of red shale exhibited three stages that were highly coupled with the stress curve: stable accumulation(linear stress increase and weak AE activity), sudden release(peak stress and sharp surge of AE signals), and dissipation(low stress level and stable AE signals). Furthermore, specimens with 30°–60° bedding angles demonstrated nonlinear stress fluctuations before reaching the peak stress, accompanied by multi-peak variations in AE signals. Additionally, an RA threshold of >8 μs·d B^–1 was proposed to predict shear slip 20 min in advance. Industrial tests showed that this scheme reduced the roof collapse rate of roadways to 9% and decreased the per-meter support cost by 1 200–1 800 yuan. [Conclusions] The bedding angle exerts a predominant influence on the anisotropy and fracture mode of red shale. The three-stage AE and RA–AF criterion effectively characterizes failure. A differentiated support scheme is proposed: roadways at 0° are reinforced with Φ22 mm high-strength anchor cables(≥150 kN); those at 30°–60° are anchored with epoxy grouting(≥5 MPa) + U-steel(45° with 0.8 m grouting spacing and AE monitoring); and those at 90° are reinforced with anchor cables + 120 mm C25 shotcrete. This approach is instrumental in ensuring the safety and efficiency of mining operations in Guizhou phosphate mines.