In 2013 there are less than 20 documented examples of operational geothermal systems on mine sites worldwide. This is surprising, since on remote mine sites, where fuels may have to be shipped in over great distances, heating and cooling from low-enthalpy geothermal sources may have a significant advantage in operational cost over conventional energy sources.A review of factors affecting the feasibility of geothermal systems on mining projects has been undertaken, and has identified the possible configurations of geothermal systems suitable for the exploration, operational and closure phases of mine development. The geothermal opportunities associated with abandoned or legacy mines are also discussed. The potential categories of heat reservoirs associated with mine sites are: natural ground; backfilled workings; mine waste, dewatering pumping; and flooded workings/pit lakes.The potentially lower operational costs for heating and cooling must be offset against the capital cost of a geothermal system. The focus for mine operators should therefore be on identifying at feasibility stage those projects where conditions are favourable for geothermal systems, where the potential risks are understood, and where the economics are likely to be beneficial, where geothermal systems can be established while minimising additional capital costs. KEYWORDS Energy, Geothermal, Minewater INTRODUCTIONThe use of geothermal technologies to extract heat energy from the sub-surface environment, to provide heating and cooling or to generate electricity, is well established outside of the mining industry, yet to date it has seen relatively little uptake within the sector. As it relies on the same blend of geological and engineering skills which mining demands, this omission is rather puzzling, and begs the question whether it represents a considered rejection or merely oversight. In appropriate geological settings, with the correct engineering, geothermal energy can be an economic source of low carbon energy, able to displace traditional fossil fuelbased energy sources, either for use within a mine, for supply to living quarters or working areas on mine sites or for sale to third parties. This paper examines the proposition that the mining industry is ripe for a significant expansion of geothermal energy use.

No abstract

Ground energy systems use the ground and groundwater beneath a site as a heat source or sink to reduce energy costs and improve the environmental performance of buildings. The design and performance of the ground element of these systems (boreholes and ground loops) are dominant factors in the capital and operating costs of the system, yet, at present, such systems are often specified with little geotechnical input. This paper reviews some of the existing design approaches from a geotechnical perspective, and identifies potential failure modes (short term, long term and regulatory related) for ground energy systems. Short-term failures may result from deficiencies in the capacity of the infrastructure forming the ground element and/or from poor connection between the infrastructure and the ground. Long-term failures may derive from misestimation of loads and/or ground parameters. Possible future directions in the design of ground energy systems are discussed, and the need for informed geotechnical input to ground energy system design is highlighted.

No abstract

In the design of a construction dewatering system in a fine-grained soil it is necessary to consider not only the steady state flow rate that must be pumped, but also the time it will take to achieve a given drawdown. This may be weeks because the soil will usually remain saturated, and the mechanism of pore-water pressure reduction is consolidation rather than dewatering per se. If the response time is not taken into account in programming an excavation, the cost implications could be considerable. In this Paper approximate methods based on the assumption that the isochrones are parabolic are developed for the estimation of time-drawdown relationships for dewatering systems in fine soils. The parabolic isochrone analyses are compared with exact solutions where these exist, and with field data from five case studies. The parabolic isochrone approximation is shown to be suitable for flow to lines of wells, and to rings of wells, provided that the distance of influence remains small compared with the radius of the ring. Lors de la conception d'un système drainant dans un sol granulaire fin, il faut à la fois prendre en compte le débit en régime permanent qui doit être pompé et les temps mis pour atteindre un certain rabattement. Ce temps peut-être de plusieurs semaines puisque le sol reste générallement saturé et que le mécanisme gouvernant la diminution de la pression interstitielle est la consolidation plus que le drainage. Si le temps de response n'est pas pris en compte lors de la conception d'une excavation, les coûts peuvent augmenter considérablement. L'article présente des méthodes approachées, fondées sur l'hypothèse que les isochrones sont paraboliques, qui permettent d'approcher les relations temps-rabattement pour des systèmes drainant dans des sols fins. Les résultats des analyses des isochrones paraboliques sont comparés à des solutions exactes, lorsqu'elles existent, et à des données n-situ provenant de 5 cas d'étude. L'approximation des isochrones par des paraboles semble adaptée aux lignes de puits et aux cercles de puits si le rayon d'action des puits est faible devant le rayon du cercle de puits.