Abstract

Rock surfaces in mining operations present varying degrees of superficial roughness, influenced by natural geological structures and the excavation methods. The topography of face lines and tunnels in mine sites present direct implications for operational efficiency and ground control conditions. Major protrusions and random undulations along faces and tunnel walls influence blast advance efficiency, access for the mining equipment, and effort required to manually or mechanically scale active headings. Pronounced roughness along mining surfaces also indicate the probable presence of overhanging lumps and similar problematic ground control conditions.

When considering mining processes, the geometry of excavations relates in large part to the mining method and mechanical equipment used. As such, the impact of surface roughness on the mining cycle is dictated by the scale of influence for the different processes considered. Meter-scale protrusions will not affect full face road headers, but may impede heading access to a jumbo-drill boom. Similarly, large undulations along blasted surfaces will induce pronounced wear and tear on mechanical scalers but remain unnoticed by hand scalers. Evaluating roughness along rock surfaces is necessary to evaluate the performance of mining processes and overall ground control conditions. For objective and systematic appraisal of rock faces, topographical assessment must take into account the scale of influence for the process considered.

The evaluation of surface roughness for operational conditions is generally a subjective and empirical process. Objective topographical assessment of surface conditions can be achieved by using modern remote sensing tools such as LiDAR or photogrammetry. The present work showcases how topographical mapping followed by scale-dependent recursive analysis can be used to quantify rock surface in mining operations. The influence of typical mining situations such as drilling inaccuracy, overbreak, perimeter blasting, and lookout angles are quantified in terms of objective scale-dependent roughness measurements. The showcased method is used to compare different mining process and evaluate the performance of overall cycle. The study investigates the influence of external factors such as the size of equipment used or the geometry of the excavation on surface roughness evaluation. A method to define a scale dependent threshold according to equipment used is introduced to evaluate surface roughness conditions. The method is applied to different types of mining equipment traditionally encountered in underground workings, including continuous miners, jumbo drills, and mechanical scalers. Cumulative passing curves representative of roughness along considered rock surfaces are used to quantify maximum and minimum scale-specific thresholds according to the mining process considered. The methodology presented is shown to present an objective and reproductible method to compare and evaluate surface roughness along rock faces while taking into account the mining method in place.