# Geomechanical Basis for Assessing Open-Pit Slope Stability in High-Altitude Gold Mining
## 2 Materials and Methods
### Analysis of Fracture Orientations and Weakness Planes
The analysis of fracture patterns along the northern pit wall revealed five primary fracture systems with the following orientations (Figure 4):  
I: A = 54\({}^{\circ}\), \(\delta\) = 80\({}^{\circ}\); II: A = 115\({}^{\circ}\), \(\delta\) = 69\({}^{\circ}\); III: A = 193\({}^{\circ}\), \(\delta\) = 75\({}^{\circ}\); IV: A = 230\({}^{\circ}\), \(\delta\) = 45\({}^{\circ}\); V: A = 280\({}^{\circ}\), \(\delta\) = 65\({}^{\circ}\), and the southern wall has eight fracture systems, as follows: I-A1 = 18\({}^{\circ}\), \(\delta\)1 = 68\({}^{\circ}\), \(n\)1 = 22; II-A2 = 116\({}^{\circ}\), \(\delta\)2 = 73\({}^{\circ}\), \(n\)2 = 8; III-A3 = 210\({}^{\circ}\), \(\delta\)3 = 79\({}^{\circ}\), \(n\) = 8; IV-A4 = 235\({}^{\circ}\), \(\delta\)4 = 81\({}^{\circ}\), \(n\)4 = 14; V-A5 = 228\({}^{\circ}\), \(\delta\)5 = 44\({}^{\circ}\), \(n\) = 11; VI-A6 = 278\({}^{\circ}\), \(\delta\)6 = 60\({}^{\circ}\), \(n\)6 = 31; VII-A7 = 310\({}^{\circ}\), \(\delta\)7 = 83\({}^{\circ}\), \(n\) = 10; VIII-A8 = 292\({}^{\circ}\), 88 = 47\({}^{\circ}\), \(n\)8 = 10, where A is the strike azimuth, \(\delta\) is the dip angle, and \(n\) is the number of measurements. The identified fracture systems at each measurement point were analyzed in terms of their influence on bench slope stability, in accordance with the existing classification system [6], based on the orientation of the slope face. The results of the slope stability assessment indicated that during the analysis of the southern pit wall within the design contour, three downward-dipping fracture systems were identified in the upper part of the slope. These may potentially lead to localized rock block failures. In this case, Failure Mode VII, according to the classification proposed by Professor [PERSON] [7], is applicable, with a calculated safety factor of 1.23. This highlights the need for increased attention during blasting operations in the pit contour buffer zone. Additionally, at observation point 3\({}^{\circ}\) 19, a longitudinal, downward-dipping fracture system was recorded, which, under specific conditions, may correspond to Failure Mode I, with an associated safety factor of approximately 1.16. Other sections of the southern slope within the 30 m design bench are considered stable, with calculated safety factors ranging from 1.96 to 32.0. According to current regulations, the required safety factor for design slopes should be no less than 1.5-2.0 [18]. Figure 4: Northern wall (**left**) and southern wall (**right**) fracture systems of the high-altitude open-pit mine. Blue crosses represent fracture measurements on the northern wall, red crosses indicate those on the southern wall. The stability analysis of the northern pit wall showed that the existing fracture network within the near-slope rock mass does not significantly affect the stability of individual benches. Even when applying Failure Mode VI from Professor [PERSON]'s classification, the calculated safety factors ranged from 3.09 to 5.98. These values meet established safety criteria, including seismic scenarios--where the reduction in safety factor under such conditions was only about 0.1. The southern wall of the Bozymchak open-pit mine is predominantly composed of granodiorites, whereas the northern wall consists mainly of marbleized limestones. The upper parts of both slopes lie within the weathering zone. Prior to slope stability assessment, justification of the mechanical properties of the near-slope rock mass is necessary. Since the internal friction angles of the same rock type determined from specimens and in situ measurements differ only slightly, they are assumed to be approximately equal: \(\varphi_{lag}\approx\varphi_{mass}\). Cohesion values obtained from laboratory testing may be several times higher than the corresponding parameters of the same rock type in natural conditions.