African Mining May 2023 | Page 31

HEALTH AND SAFETY •

SCAN 1 SCAN 2

Herewith a direct comparison of two SSP scans overlain onto a photo of the area scanned – three benches . Scan 1 – with a flat top-edge finish – shows the result without topographical correction ; while Scan 2 – staggered at the top with topographical correction applied – indicates the same scan path and red areas showing geological structures , which are clearer and connected now , making the holistic analysis of these structures less complex and easier to understand .

attempt to remove loose rocks that pose a FOG hazard . ² However , it is within the scope of unseen structures – one to multiple metres deep within the rock mass – where Reutech ' s current ground penetrating radar ( GPR ) enables the identification of structures to be managed to prevent potential unidentified , beyond surface , FOG issues caused by structures not observed easily on the surface of the excavation . ³

GPR works by sending a waveform into the rock mass , which is then reflected back by structural changes in the rock . The company currently uses GPR tech and RF ( Radio Frequency ) in a patented hand-held device they already supply to the industry – the SSP ( Sub Surface Profiler ) designed specifically for underground mining operations . Its light-weight design enables one-handed operation by one person in much the same way as a paint roller , said Greeff . The data collected is wirelessly transmitted and processed in real-time , giving instant feedback on rock structures to a second operator underground , reading the feedback digitally on a tablet while scanning is taking place . The objective is to enable directives following the scanning to achieve optimal utilisation of roof support mechanisms in an environment where every second counts .

“ The current tech allows us to pick up structures deeper within the rock mass to alert the team to these , as it relates to the possibility for instability , such as gravity falls and excavation drift , which may ultimately be exacerbated by seismic energy ,” Greeff explained . “ A solid dark mass is nothing to worry about , while the red highlights the area of issue .”

Sub Surface Profiler ( SSP ).

Tech challenge and solution However , traditional GPR has two practical challenges . One is that data interpretation can be tricky for the untrained eye , and two , an uneven rock surface , which is the reality most of the time , distorts the scanned image , making identification and therefore assessment more difficult . Easy data interpretation is therefore the new end goal , as typically , distortion of the scanned structure occurs because while the SSP scans across the rock surface , the distance that the GPR is away from the structure being scanned changes over time , thus warping the image .

Reutech has proposed ' topographical correction ' as an add-on to the current SSP technology to enable a clearer picture with the objective of making data interpretation easier and decision-making faster by the user . In mapping the topography of the rock mass , as one scans with the SSP , one assumes it is scanning a single line , and that line should resemble the topography scanned , which is not the case because of the reality of an uneven rock surface . The idea is to map the vertical movement of the SSP and , on the back-end , record the inertia and movement of the SSP . The result will be in an inertia measurement unit ( IMU ) to record the movement of the platform while combining it with data received from a scanning GPR antenna . This allows the position of the platform , versus the object it is observing , to be plotted in parallel .

Direct and immediate benefit The direct and immediate benefit of the SSP is the ability to identify rock hazards beyond the excavation skin that are not visible to the naked eye . This is achieved through the production of a graph that depicts the roller as it is dragged across the rock surface , with the x-axis recording the distance scanned and the y-axis recording the depth into the rock mass of the structure . The red in the image indicates a reflected structure , which is interpreted as a typical fault or crack in the rock .

“ The structure identified in this particular image supplied could create a wedge that falls out or a plane where the rock face could dislodge . Depending on the width of the excavation , this could create a fairly large FOG . Now that the mining team is aware of the deeper structures , not observable on the excavation skin , but observed with the help of the SSP and topographical correction , the structure detected can be fully assessed and understood .