## 3 Mechanical Properties of Norite
### Strength Parameters  
Rock strength properties are significantly affected by weathering, which is often linked to surface exposure or near faults and shear zones, leading to increased clay content and porosity [28]. Additionally, joints and fractures caused by regional stresses and digging up create planes of weakness, allowing fluid passage and contributing to further alteration [42]. [PERSON] et al. [7] (2022) define shear strength as the ability of a rock to resist shear forces or the point at which it fails due to shear stress. Therefore, when the rock is subjected to shear load, it slides along a plane, causing failure parallel to that direction. Uniaxial compressive strength (UCS) is the maximum axial stress a material can withstand under uniaxial compression before failure occurs. UCS is an essential mechanical property, measured by applying a compressive load to a specimen in a controlled laboratory setting until failure occurs, at which point the maximum stress is calculated [43]. Uniaxial compressive strength (UCS) is commonly measured in laboratories, but alternative methods such as the point load index and field press are also used in practice [44]. UCS testing involves compressing rock cylinders parallel to their long axis, with the accuracy of the test relying on flat, perpendicular plane surfaces [45]. The strength of the sample decreases with an increasing length-to-diameter ratio, and failure typically occurs at a strength lower than the sample's maximum UCS; failure also occurs due to rapid energy release. Errors can arise from frictional effects at the platen contact, and in strong materials, both longitudinal splitting and shear fractures may occur [46]. The study by [PERSON] et al. [1] (2005) outlined that the UCS of norites in the Merensky Reef ranges from under 100 MPa to over 200 MPa, with an average of 150 MPa for the freshest rocks. The tensile strength (TS) of norites ranges from less than 5 MPa to 15 MPa, with a mean of 11 MPa, classifying most norite rocks as strong to very strong [1; 31]. In Figure 5, [PERSON] et al. [1] (2005) conducted UCS testing on igneous rock samples where a 60 mm diameter core typically failed along a plane angled at less than 45\({}^{\circ}\) to the vertical compression axis. The failure modes observed included (a) failure along a single plane, (b) failure along a single plane with high-angle longitudinal fractures, and (c) failure along two fractures symmetrically inclined to the longitudinal axis. Rock failure modes are influenced by factors such as mineral composition, stress distribution, material strength, and testing conditions, which are essential for predicting rock behavior in mining. The unique composition of norite results in distinct failure modes [1]. Shear planes can be either continuous, extending smoothly across the material, or discontinuous, breaking at certain points [31]. The findings of this study are significant as they focus on norite, specifically from the Bushveld Complex, which is the same subject of this research. Moreover, both studies observe similar behavior in norite under uniaxial compressive strength (UCS) testing. A 60 mm diameter core was used for UCS testing, with samples typically failing along a plane inclined at less than 45\({}^{\circ}\) to the vertical compression axis (Figure 5). According to the ISRM guidelines, the recommended loading rate for standard UCS testing is between 0.5 and 1.0 MPa/s. The tensile strength is the maximum stress a material can withstand when pulled before breaking. The direct tensile strength is measured by applying a uniaxial tensile load to a specimen until it fractures; in contrast, the Brazilian tensile strength is determined by applying a compressive load to a disk-shaped specimen, causing it to fail in tension [47]. The study of [PERSON] and [PERSON] [48] (2014) reviewed rock tensile strength to investigate the relationship between direct tensile strength (DTS) and Brazilian tensile strength (BTS).