Raise Bore Vertical-Drop Scan: Cavity Scan


Not for disclosure



Type of Scan

Hovermap off-drone vertical drop-raise bore scan


Due to unknown causes, an underground mine in Zimbabwe had been experiencing scaling and bulging on the walls of their raise bore. To understand the extent of the bulge and ultimately resolve the scaling, Dwyka Mining Services, as authorized distributors of the Hovermap SLAM-based technology were called in for assistance.

Since it is unsafe for mine personnel to physically inspect the raise bore, the mine initially attempted to retrieve geometrics of the bulge using a robot with a camera attached to it, however, due to low lighting and the camera’s limited functionality, the camera footage was not able to give a full 3D picture of the raise bore.  With Hovermap’s versatile capability, a 3D LIDAR point cloud scan was possible by attaching the Hovermap to a raise cage and gradually dropping down with a cable as shown in Figure1.

Figure 1 Hovermap attached to a raise cage


The primary goal was to establish if there was scaling on the walls of the raise bore and if there was, what the extent of the void or ‘bulge’ was. In order to collect this data from inside the raise bore, Dwyka Mining Services as Authorised African resellers of Emesent’s Hovermap and supplier to the mine carried out the scanning project.

Hovermap is an industry-pioneering on- and off-drone payload that provides real-time SLAM LiDAR mapping, omnidirectional collision avoidance, GPS-denied flight and advanced autonomy. Upon examining the condition of the raise bore, an off-drone, raise cage mounted application of the Hovermap was used to safely retrieve data from the raise bore.

The capability of the Hovermap to deliver 300,000 points per second (p/s) made it possible to achieve a high-density point cloud with a single 15-minute drop of the Hovermap into the 70m long raise bore.

Figure 2 Raise bore point cloud

Figure 3 HovermapTM live point cloud of the raise bore

Figure 4 Seepages of apparent water displayed on the point cloud

Figure 5 Extent of the ‘buldge’in the raise bore

Figure 6 Geometrics of the raise bore

Figure 7 Depth at which the ‘bulge’ occurred from surface

Figure 8 Volume of the raise bore

Figure 9 Volume of the ‘bulge’ for remediation calculations


With the use of a tablet, connected to the Hovermap over Wi-Fi, visuals of the real-time point cloud were used to determine the depth at which the bulge was occurring, hence guiding the distance at which the raise cage drop was dropped. With the accurate geometrics of the point cloud, the client was able to determine the volume of concrete and shotcrete required to fill the ‘bulge’ on the raise bore.

With Hovermap’s ability to visualise variance in intensities of different surfaces, seepages of what appeared to be water were observed from the point cloud. This assisted the mine to infer that water coming from the ventilation fans could have caused the expansion in the raise bore.

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