Scanning experience in underground copper ore mines at KGHM Polska Miedz S.A.

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1 Scanning experience in underground copper ore mines at KGHM Polska Miedz S.A. Ryszard HEJMANOWSKI Agnieszka MALINOWSKA AGH University of Science and Technology /Poland Grzegorz Patykowski Jacek Młynarczyk Łukasz Markiewicz KGHM Polska Miedz S.A. /Poland Key words: laser scanning, mine surveying, copper ore Abstract At the beginning of 2012 in the mines of KGHM Polish Copper SA started the implementation of laser scanning of underground mine infrastructure. These survey have been used in the design and conduct of mining planning. A scanner Leica C-5 with unlocked function of the range and speed of scanning has been implemented. The paper presents the experiences and examples of the use of this technology. 1.Introduction Numerous technological solutions and data mining methods have been tested in the Lubin Copper Ore Mine over tens of years. One of them is a laser scanner for 3D modelling of drifts and all types of technical infrastructure. This new technology allows for determining the siteheight location of millions of points in a short time (Sturzenegger, Stead, 2009; Van der Merve, Andersen, 2012). Such an output is unattainable for the present measurements based on electronic tachymeters and definitely exceeds classic surveying methods by the quality of obtained data. By implementing this technology to mining geodesy one can learn the advantages and limitations of the laser scanning method. The obtained results prompt a conclusion that this technology shall considerably broaden the application field of geodesic surveys in copper ore mines and spur certain changes in the approach to cartographic documentation of mine operations. 2. Laser scanning in Lubin Copper Ore Mine After a few years' observations of the laser scanner market and test measurements in mine's conditions with the use of instruments produced by leading manufacturers, a decision was taken to use the Leica ScanStation C5. This instrument is a platform which can be further developed at any time of using it. Owing to means for the realization of this purpose, initially the scanner was supplemented with two out of four possible options: the range of measurements was broadened from 35 m to 300 m, and the rate of scanning was increased from 25,000 pts/s to 50,000 pts/s. In this way the number of measurement points can be lowered and the output of measurements increased by reducing the time of field works. Applications for processing clouds of points are an important element of the 3D model. This task is realized by incorporating the module software Leica Geosystems HDS Cyclone and Microstation with a set of applications MDL dedicated to the work in a cloud of points, i.e. Cloudworx, Pointools. Over a six month's work on various types of projects with the use of TLS technology brought about more than 100 GB of measurement data. Five kilometers of mine drifts and a large number of technical infrastructure were measured.

2 The specific character of the mine objects does not allow for a simple implementation of measurement technologies and methods used on the surface, e.g. GPS technology cannot be used for geoorientation in underground mine conditions. Each time, before realizing a given task, one should analyze the possible ways of using the results and select the respective performance technology, covering, among others, georeference issue, which is equally important as the scanning process itself. An important aspect hindering the use of the laser scanning technology in deep conditions is frequently the limited size of objects which have to be stocktaken. The space of the drifts is occupied by specialist equipment and infrastructure, which additionally increases the scope of work to be done to find extra space for the scanner and optimally localize signals connecting the scans, much more than in the case of surface arrangements. As far as the work involved and difficulties in the realization go, the projects realized in the mine's conditions can be compared only with stocktaking of complex industrial installations (Fekete at all, 2010). When designing each measurement series with the use of a surface scanner it is important to analyze physical conditions in the investigated places, i.e. air humidity, temperature and dust content. Despite these disadvantages, relatively short time of use of scanner in the Lubin Copper Ore Mine and constant tests, our long experience in mining measurements makes us conclude that the TLS technology is a must nowadays. 3. Exemplary laser scanning applications 3.1 Scanning voids in the rock mass An example of laser scanning is stocktaking of geological phenomena of karst character, which were found in preparation drifts in the south area of the Lubin Copper Ore Mine. In this case the characteristic of stocktaken objects requires a unique technology. Among the dominating inconveniences were the limited space and lack of stability of signals used for connecting scans, which increased the time-consumption of preparation works preceding the measurement itself. Besides, the complicated shape of the beds and their considerable branching made the designers adjust the measurement points configuration to the geometry of the object. The analysis of the results reveals that a laser scanner can be used even in small objects of complex shape (pic. 1). Its only limitations are the size and weight of the device itself, which hinder moving of the device in narrow spaces, and manual operation, at least at stage of development. Pic. 1. Karst effect in the neighborhood of mine drift

3 3.2. Scanning mine drifts in the area of near shaft station L-I The aim of this project was testing the possibilities and efficiency of laser scanning in real underground mine conditions. The selection of drifts in the near shaft station area is conditioned by, among others, easy access for scanner and other accessories to the measurement point; besides the near shaft station areas have a rich network of drifts with complex spatial organization, differing in size and equipped in numerous technical infrastructure. All these aspects make the place an ideal research area for testing this new technology (pic. 2). Pic. 2. The part of 3D model of mine drifts near to shaft station The spatial model presented in pic. 2 is a result of incorporating data from 64 scanner points (7 measurement days), and the number of data equals to about 570 million points. The source data occupied about 19 GB. Each time, prior to the scanning operation, georeference was made by tachymetric measurement of HDS discs. After scanning these discs helped localize the scanned surface in geodesic coordinates system. Connecting images from particular scanner points was made with the use of special spherical signals, mounted on the casing, side walls or elements of mine's equipment. The spatial relations of centers of at least three spheres, scanned from two neighbouring points, help to automatically connect individual clouds of points. Judging from the experiences gained so far, this measuring method turns out to be optimal as far as accuracy, efficiency and simplicity are concerned. The realization of the project reveals that the scanner points can be distributed every ca. 50 m, and so in line with the geometry of typical cross-drifts in KGHM mines, where ventilationmaneuver cross-drifts are linking drifts of a given bundle. Obviously, the accuracy of representation of terrain details decreases with the increasing distance from the scanner. However, at the 'average' scan resolution and maximum distance of 25 meters from the scanner the scanning grid is 25 mm x 25 mm in the tested technology, which in the authors' opinion is sufficient for the 3D modeling of drift. Although the unfavourable exposition of stocktaking drift surfaces to the laser beam, connected with relatively low reflection coefficient additionally results in a lowered accuracy of measurement of terrain details, this effect is partly neutralized by superimposing images from one or more neighbouring points. Summing up, the applicability of PLS technology to stocktaking of mine drifts seems to be both feasible and purposeful. However, one should not forget to concurrently conduct sufficiently accurate situation-height geodesic web, fit for the assumed laser scanning results. In the lack of appropriately accurate web in the drifts, where the scanning is planned, the geodesic web should be concurrently introduced only for the sake of geoorientation of scans.

4 3.3 Stocktaking of south retention tank Within the periodic control and necessary maintenance works, the south retention tank was scanned and its spatial model was made (pic. 3). As a result complete information about the measured object was obtained and cross sections were performed by the user of the object (pic. 4). For the reason of imparting a digital version of this model to other mine services, the data were exported to a file *.u3d. This is a popular file *.pdf which can be used for 3D operation. In this case simple measurement tools and possibility of making cross sections are at our disposal. In this way the advanced software does not have to be used, and the related high costs and professional operator avoided. Pic. 3. Scan views of the south retention tank Pic. 4. TIN model of the south retention tank 3.4. Attempts at scanning mine shafts Within the stocktaking of mine drifts in the shaft station area the mine shafts were stocktaken with the use of the TLS technology (pic. 5). The first attempts reveal that despite the high

5 number of elements in the shaft, unfavourable conditions and geometry of objects, the laser scanning seems to be appropriate for stocktaking the mine shafts. The most important problem, beside the ones mentioned previously, will be providing proper georeference so that the obtained accuracy is sufficient in view of the respective regulations. Of course the laser scanning method may turn out to be inapplicable in some of the shafts due to their conditions and other limitations. However, in the case of positive results of tests with the laser scanner the amount and quality of data obtained in this way may radically increase the knowledge about the technical state and mining-induced deformation processes. Pic. 5. Part of a scanned shaft 3.4 Stocktaking of heaps and stockpiles Another tested application of TLS, which is not directly connected with the idea of creating 3D models of mine drifts was the use of this method for stocktaking of heaps and stockpiles. In this case the winnings produced by the mine and stockpiled in the storages were measured. Properly selected measurement techniques and data processing methods allowed for obtaining accurate information about the cubature of the stockpile in a relatively simple way. The created model of the stockpile enables one to make a number of interesting analyses (pic. 6). The laser scanner technique used for this type of tasks, when a similar amount of work is spent on field operations and data processing brings about more complete and more accurate results as compared to the classical methods. In the case of stockpiles of complex geometry, the scanning method may lower the amount of work involved, especially as far as field measurements are concerned. Pic. 6. A stocktaken copper ore stockpile

6 4. Conclusions The results of the discussed tests reveal that the TLS technology is definitely suitable for documenting operations in an underground mine. Among the most important advantages are: - measurement does not have a point character. Its spatial character allows for generating an arbitrary horizontal or vertical cross section, without need to remeasure. - scanning does not exclude the present measuring techniques; it supplements them. - scanning accelerates measuring activities in particularly dangerous places (cavers, retention tanks). - automation of measurement eliminates human errors and negligence; measurement can be realized regardless lightening conditions. - fast measurements of large objects, frequently hardly accessible, provide reliable feedback from all stages of the project. - measurement does not have side effects, and there is no need to withhold regular mining operation. Concurrently with the measurement functionality TLS tests, the TLS method was also tested for issues related with the mine operation. Among tasks to be solved are transmitting and sharing data with other sections of the mine. There are available solutions on the market thanks to which the scanning results can be used by a larger number of users through a limited-functionality free browser. This solution has some drawbacks and prior to its implementation some additional measurements checking out the reliability of its results have to be introduced. Another question to be asked refers to the spatial range of the mine to be stocktaken in such a detail. With all its great possibilities, the TLS technology still has some technological and informatics limitations. Aknowledgment This paper was submitted thanks to the founding from the project AGH UST N o Literature Sturzenegger M., Stead D.: (2009) Close-range terrestrial digital photogrammetry and terrestrial laser scanning for discontinuity characterization on rock cuts. Engineering Geology, Volume 106, Issues 3 4, 12 June 2009, Pages Van der Merve J.W., Andersen D.C.: (2012) Application and benefits of 3D laser scanning for the mining industry. The Southern African Institute of Mining and Metallurgy. Platinium Fekete S., Diederichs M., Lato M.: (2010) Geotechnical and operational applications for 3-dimensional laser scanning in drill and blast tunnels. Tunnelling and Underground Space Technology. Nr 25, pp