This study aims to accurately determine the geomechanical parameters of the rock mass an‎d eva‎luate the stability of underground excavations at the Kolah-Darvazeh mine. Understan‎ding the mechanical behavior an‎d properties of the rock mass is fundamental for the safe design of underground workings, mitigating the risk of collapse, excessive deformation, an‎d associated hazards in deep mining operations. A total of 40 rock samples were collected from various mining levels, an‎d a comprehensive suite of laboratory tests was conducted. Mechanical testing included uniaxial compressive strength (UCS), triaxial compressive strength (TCS), an‎d Brazilian tensile strength tests, while the dynamic properties were assessed using ultrasonic pulse velocity tests. The experimental data enabled the determination of key rock mass parameters, including static an‎d dynamic Young’s modulus, Poisson’s ratio, cohesion, internal friction angle, an‎d parameters of the Hoek– Brown failure criterion. These parameters were subsequently employed as input data for numerical modeling. Two-dimensional numerical analyses were performed using Phase2 software, applying both the Mohr–Coulomb an‎d Hoek–Brown constitutive models to the 1535-meter level workings. The simulations aimed to investigate the deformation behavior an‎d stability of the underground excavations under in-situ stress conditions. The results indicated a maximum roof displacement of approximately 4 mm an‎d a factor of safety greater than 1.5 in critical zones, demonstrating that the current support systems provide adequate stability for the existing underground structures. Integrated laboratory an‎d numerical analyses further revealed that, despite a decrease in uniaxial compressive strength with increasing depth, enhanced cohesion, internal friction angle, an‎d improved dynamic properties contribute to a more resilient an‎d stable rock mass behavior. These findings are critical for the design of safe underground workings an‎d for anticipating support requirements at deeper mining levels. In conclusion, the existing workings are currently in a stable condition. However, as mining operations extend to lower levels, continuous monitoring of geomechanical parameters, reassessment of support systems, an‎d design of more robust excavation supports will be essential. This research provides a foundation for optimized an‎d safe extraction planning in similar mining conditions an‎d offers a basis for further studies on the dynamic an‎d mechanical behavior of rock masses at greater depths.

لهراسب فرامرزي , راحب باقرپور

سعيد مهدوي , امين ازهري