Faculty of Engineering and Built Enviroment School of Mining Engineering 0315711f musakale@egoli.min.wits.ac.za / Rockfalls are a significant risk in open pit mines. Once movement of a rock perched on the top of a slope (bench) has been initiated, the most important factor controlling its fall trajectory is the geometry of the slope (bench). The best possible knowledge of rockfall trajectories and energies is important in order to determine accurate risk zoning and for the design and construction of adequate defence systems near the threatened areas. This study attempts to determine the influence of bench geometries, and the coefficient of restitution of rock, on rockfall behaviour. A study of literature was carried out to review previous studies and other relevant information on rockfalls and their analysis. The literature may be divided into two categories: experimental methods involving physical modelling, and computer models involving rockfall analyses using computers analysis methods. Rockfall computer simulation is considered to be applicable, quick to carry out and reproducible. The accuracy of the results depends on the knowledge of site conditions and slope geometry. The use of the Modified Ritchie criterion for the design of catch benches in open pit mines was also investigated. The assessment of bounce height, maximum run-out distance and kinetic energy achieved during the fall of rocks on the catch bench were the bases of the evaluation of the results obtained in this project. The computer program, Rocfall Version 4, was used for the purposes of the research. The following parameter variables were considered in the analyses: three types of rock; slopes with three stack configurations; four bench heights; and four bench face angles. The results show that, for all stack configurations and rock types, the maximum runout distance and maximum bounce height increase as functions of bench height at a specific bench face angle. A single bench configuration provides a maximum run-out distance of falling rocks larger than the value determined using the Modified Ritchie criterion for all rock types and bench face angles. Multiple bench stack configurations provide maximum run-out distances less than the value determined using the Modified Ritchie criterion only for the 90o bench face angle in all rock types; those with 60o, 70o and 80o bench face angle provide a larger maximum run-out distance. Therefore, the validity of the Modified Ritchie criterion for the design of catch bench widths in open pit mines with inclined benches must be questioned. According to Ritchie’s study (1963), rocks that fall in trajectory (free fall) seldom give high bounces after impact on a catch bench. This project shows that this finding is valid for rocks with low coefficients of normal restitution. Rocks with lower coefficients of normal restitution provide larger run-out distances with flatter bench face angles compared with rocks with higher coefficients. In contrast, rocks with higher coefficients provide larger run-out distances than those with lower coefficients for steeper angles. The consideration of the influence of geometry (shape) of falling rocks on rockfall behaviour showed that, for a flatter slope, as could logically be expected, the maximum run-out distance is greatest for rounder rocks and smallest for flatter slabby iv rocks. This is due to the fact that on a flatter slope, the mode of falling of rounder rocks is rolling down the slope. This mode provides essentially no resistance to motion, resulting in largest maximum run-out distance. In contrast, for long flat slabs, the mode of movement will be sliding, which results in a smaller maximum run-out distance. The maximum run-out distance as function of rock shape reduces as the normal coefficient of restitution increases. For all rock types, the maximum bounce height reduces as a function of the friction angle for flatter slopes. This is due to the fact that rocks are in contact with the slope during the rockfall. As the coefficient of normal restitution increases, an increase in the maximum bounce height results.

Liquid fuel injection is a critical mechanism for the deliverance of liquid fuel in contemporary aircraft propulsion combustion systems due to its outsized influence in providing optimal combustion conditions and improving overall aircraft efficiency and performance. Despite this, these liquid jet in crossflow (LJIC) systems are highly variable due to conditions in the jet and the surrounding airflow, leading to variability in performance behavior and inconsistency in fuel mixing and combustion efficiency. This has prompted the introduction of solid pintile obstructions of novel designs to provide a more flow-independent fuel injection scheme and decrease variability of the jet properties against a range of crossflow conditions. This thesis will examine the effects of a solid pintile obstruction on the behavior of an LJIC injection in a typical ramjet combustion configuration, with a focus on the face angle variations of these pintiles. Two pintiles, with face angles of 60° and 120°, will be tested against a no-pintile control configuration under a range of relevant operating conditions and observed under a novel method of 3D-imaging in the x-z plane view. The investigation is designed to understand the effects of these pintiles in the context of broad shifts in the momentum flux ratio and Weber number across a broad range of vitiated and non-vitiated environments. Results demonstrate the significance of the pintiles on the trajectory and performance of an LJIC injection. Building upon previous investigations on the influence of various pintile dimensions, the face angle was found to play a similarly critical role in the influence of the LJIC injection. Overall, the 120° wider face angle appears to be most optimal in enhancing crossflow interaction and promoting flow-independence compared to the 60° face angle. Future research on narrower and wider face angles and the relationship between the face angle and other design parameters could further improve LJIC injection performance and flow-independence.

The comparison of rheological properties (complex shear modulus and phase angle and dynamic viscosity) of four paving bitumens and two polymer modified bitumens is performed in this diploma thesis. Furthermore, the empirical tests (needle penetration and softening point) were determined on these binders. Effect of asphalt binders aging was modeled using RTFOT test and modified RTFOT test (3 x RTFOT).