UNEXMIN

Background overview on flooded mines and dewatering

Mining is an activity that can last from a few years to several decades, after which a mine is closed. Mine closure is the process of stopping, temporarily or not, mining operations. This happens, usually, when the mineral resource (or resources) of a mine is depleted or operations are no longer profitable. Commonly, a mine gets flooded when its operational life ends – for both open pit and underground mines -, because its maintenance systems also stop – dewatering systems cease to operate. If there are no drainage adits at the lower levels of the mine, the working space will be filled with water and the mined spaces flooded with ground or surface waters. The flooding process in a mine can last from some months to more than a decade, depending on factors such as accessible open space, availability of infiltration water and on the type of flooding – controlled, uncontrolled or monitored.

If a mine is flooded or getting flooded, which is constantly happening during mine operations, dewatering techniques must be applied. Today, the dewatering systems and techniques for both open pit and underground mines are well defined. Because of the great evolution that happened with the dewatering techniques, even mines with thousands of meters deep can be dewatered when and if needed. However, the act of dewatering flooded mines may present a lot of problems: environmental concerns related to acid mine drainage, dispersal of contaminated water and type of technology to use and even the need to drain flooded mine shafts during mine disaster rescue attempts.

Concept and approach

In Europe, it is estimated that there are 30,000 closed mine sites and many of these may have considerable amounts of essential raw materials. These leftover minerals usually are the ones that were disregarded during the operational life a mine. It is a usual symptom of mining: the mines are closed not because of mineral depletion, but mostly because of economical and technological constraints, parameters that suffer fluctuations with time. Other parameters that establish closure of mines are accidents, war or political reasons and environmental constraints. Today, however, it could be feasible to explore the minerals that were left behind and that may now become essential resources for the European raw materials’ market pool. Many of these closed mines are now flooded and the last piece of information of their status and layout is decades or more than a hundred years old. The complex underground layout, topology and geometry of most underground mines, make it impossible to do any surveying by conventional or remotely controlled equipment. One of these examples is the usage of human divers, which can prove unfruitful and even lethal in harsh deep mine conditions.

Objectives

The main objective in UNEXMIN is to develop a fully autonomous multi-platform Robotic Explorer, that will use non-invasive methods for 3D mine mapping on flooded and deep mines, otherwise inaccessible, in Europe. This work will lead to new and valuable geological and mineralogical information that may result in important decisions on the future of Europe’s raw materials. UNEXMIN’s pioneer developing technique could open new exploration scenarios for European abandoned mines, with the help from actualized data that cannot be accessed any other way. Specific goals of the UNEXMIN project are as follows:

These major objectives will be supported by a science and technology merger of deep sea robotics solutions with user’s requirements from the mining industry. They will lead to a fine adaptation of UX-1 so that the novel developed technology could best serve end-users.

Technological challenges

The Explorer will need to employ a wide range of robotics technologies and cutting-edge knowhow from deep sea underwater robotic systems, 3D map reconstruction, control and navigation, autonomy and other areas of interest. The technologies will be adapted to and tested in real mine conditions, integrating imaging and other non-destructive, non-invasive surveying technologies and measurement methods that will provide valuable information on the status of these inaccessible areas. Recent developments in autonomy research will allow the design and development of a new class of mine explorer service robots, capable of operating in real mine conditions without remote control.

The deployment of a multi-robotic system in a confined environment, such as a flooded mine, inherits a lot of challenges and problems that must be overcome so that the robots can work autonomously in such spaces, without damaging the equipment and the mine itself. The most important challenges that must be overcome in UNEXMIN are:

The first prototype of the robot will be preceded from component validation and simulations, to first understand the behavior of technology components and instruments in the new environment it will be used. At the same time post processing and data analysis tools will also be developed, including pre-operational trials which will be launched in real conditions.

The final stage of UNEXMIN’s project will lead to deployment of extensive pilots, during which UX-1 will be improved after each trial session, always testing it on harsher and harsher conditions. The last step of this process will culminate with the hardest challenge: resurveying the entire flooded section of Ecton mine. The robot’s development process is meant to be spiralling with continuous upgrades that are implemented in parallel with more and more complex field pilots. This will demonstrate the Platform’s scalability from small missions to the larger ones by increasing the number of deployed autonomous drones, and supporting multi-robot cooperation in confined 3D spaces with real-time sensor and data fusion for reliable navigation and communication.

Test sites

The multi-robot platform will be designed, built and then tested and validated in real-life conditions in four mine test sites, with increasingly harder conditions. The mines that will be used as test sites during the project lifetime are (in temporal and difficulty order):

Ecton Mine, that will be the last test site for UX-1, will result in a resurveying of the flooded mine workings that nobody has seen for more than 150 years and that will bring important geological information.

Partners

In this European project, a total of 13 institutions from 7 countries are collaborating to develop a new technology. The partners are:

1. University of Miskolc (UM), Hungary
2. Geological Survey of Slovenia (GeoZS), Slovenia
3. Tampere University of Technology, Department of Mechanical, Engineering and Industrial Systems (TUT), Finland
4. Universidad Politécnica de Madrid, Centre for Automation and Robotics (UPM-CSIC), Spain
5. La Palma Research S.L. (LPRC), Spain
6. Institute for Systems and Computer Engineering of Porto (INESC), Portugal
7. Resources Computing International Ltd (RCI), UK
8. Geoplano (GEOP), Portugal
9. Ecton Mine Educational Trust (EMET), UK
10. European Federation of Geologists (EFG), France
11. Geo-montan (GEOM), Hungary
12. Empresa de Desenvolvimento Mineiro (EDM), Portugal
13. Idrija Mercury Heritage Management Centre (CUDHgI), Slovenia