A Historical Perspective of Diamond Mine Dewatering Design and Guidelines for a Modern Diamond Mine

Dewatering is an important consideration in kimberlite mining. Early underground mines used water tunnels connected by passageways to divert rainwater and near-surface groundwater from the mine workings. Shafts with multi-stage pumping levels were used to pump water from the deepest mine sections. At the Finsch mine, a 650 m deep water ring-tunnel (combined with a conveyor belt level) and deep pumping boreholes were used to dry the initial block cave to 720 m below the surface. Other mines use rings of surface-pumped dewatering wells (e.g. the Letlhakane and Orapa mines in Botswana). This paper summarises the techniques used to manage pit and underground water, its links with mud rush occurrence, and lessons learned over the last 120 years. The hydrogeology of typical kimberlite mines and various ways to keep water away from the mine workings are described. The paper concludes with a good practice dewatering design and water management strategy for modern mines.

     

Calculation of mine water inflow using interactively a groundwater model and an inflow model

The uncertainty of the pre-evaluation of potential ground water inflow rates in underground mines results in difficulty in planning and costing the water related activities of the mines. This paper presents a procedure for making a rational assessment of the potential inflows. The method is based on an interactive operation of two computer models: an inflow model and a ground water finite element model. Both are first calibrated using existing information obtained from aqui fer monitoring. In a second phase, the models prelict the potential inflows as well as the impact of mine dewatering on the piezometric surface. Both the models used are based on a non linear relationship between tonnage mined and inflows. A phased behaviour in the rates of inflow increase is noted. The interactive mode of operation of the models results in confidence in the prediction because the models output (calculated inflow rates and piezometric levels) during the calibration phase are checked against the historical data. It is concluded that the method can provide mine management with guidelines for dewatering requirements under the condition that reliable data on the history of piezometric levels be available.     

Application of analytical solutions to simulate some mine inflow problems in underground coal mining

The paper considers the interaction of ground water flow characteristics, aquifer parameters and mining geometry in order to estimate mine water inflows. The ground water flow conditions include both steady and unsteady state flow in an infinite and finite aquifers to an imaginary pumping out well. Both linear and non-linear flow equations are discussed. The application of non-linear equations has indicated that with the use of appropriate terms in these equations both laminar as well as turbulent inflows can be simulated. Water inflow to underground dewatering tunnels are also discussed in terms of both laminar and turbulent flow. Mine water inflow to a mine discharging to multiple dewatering outlet is also included. The application of various techniques outlined enables a more realistic estimate of water inflow to be made which can be conductive to planning mine dewatering systems with reference to economics and safety.     

A Survey of the Geochemistry of Flooded Mine Shaft Water in Butte, Montana

Abstract.  This paper outlines general trends in the geochemistry of the more than 10,000 km of flooded underground mine workings in the Butte mining district. The waters in question range in pH from 4 to 8, are all moderately to strongly reducing, and show a huge range in concentration of dissolved metals such as Al, As, Fe, Mn, and Zn. Metal concentrations and total acidity are highest in the Kelley mine shaft, which was the main dewatering station used to pump ground water from the underground mine complex during active mining operations. In contrast, metal concentrations are much lower in the outer portions of the district where many of the mines contain hydrogen sulfide formed by sulfate-reducing bacteria. In comparison to the other heavy metals, concentrations of Pb and Cu are quite low in the flooded mine shafts. An interesting inverse correlation between pH and water temperature is noted, which may be partly caused by exothermic pyrite oxidation reactions in the central portion of the district.     

Water regime control in mines and quarries in the USSR coal industry

The paper briefly reviews the mine water problems associated with coal mining industry in the USSR. Statistics regarding quantities of water discharged from surface and underground coal mines are given together with the pumping heads, range of water problems at a coal face and the quality of mine water. Ground water control systems are described which include surface preventive measures, surface mine water control techniques and underground mine dewatering methods. Recommendations for further investigations for solving a variety of mine water control problems are included.     

Environmental impacts of deep opencast limestone mines in Laegerdorf, Northern Germany

Deep opencast mines for limestone of Upper Cretaceous age in the northernmost state of Germany, Schleswig-Holstein, greatly impact the local environment. In three pits with depths of nearly 100 m, mine pumping affects deeper aquifers and sometimes shallow ones as well. The total amount of mine water pumped ranges up to 6^*10⁶ m³/year. Due to the relief of hydraulic pressure, saline water is ascending from deeper parts of the limestone and infiltrating into the pits via the minefloor. The salt content of the deep ground water exceeds that of the sea in some places. The saline water causes process engineering problems and adversely affects the water quality of a receiving channel. Shallow aquifers are affected by dewatering due to hydraulic connections to the limestone. In places with organic soils (mostly peat of Holocene age), this is followed by ground subsidence, which damages buildings and agricultural drainage systems.     

Natural Radioactivity in Polish Coal Mines: An Attempt to Assess the Trend of Radium Release into the Environment

The highly mineralised formation waters in the coal mines of Poland’s Upper Silesian Coal Basin contain natural radioactive nuclides, mostly radium. The ²²⁶Ra concentration in the groundwater that flows into the underground mine workings reaches 390 Bq/L, and is sometimes exceeded by the ²²⁸Ra concentration. The radium-bearing water sometimes also contain barium ions, which enables coprecipitation of barium-radium sulphate. Another type of radium-bearing water contains sulphate ions instead of barium; in this case, radium is transported to settling ponds and downstream. We have assessed the daily activity of radium in waters flowing into the underground mines and being discharged to the environment. Based on 1995 data, we estimate that the total activity of radium isotopes flowing into the mines was about 1300 MBq/day, while the radium activity in the discharge waters was about 700 MBq/day. A similar assessment performed with 2016 data indicated that the total activity in inflows was roughly 1150 MBq/day, while that discharged to surface waters was about 450 MBq/day.

     

Using a Water Balance to Determine the Source of Water in the Flooding Underground Mine Workings of Butte

Abstract.  Nearly 10,000 miles (16,000 km) of underground mine workings began flooding on April 22, 1982 when the large pumps used to dewater the mines of Butte, Montana were shut off. In the first few months, water levels in the workings rose hundreds of meters. Flooding continues to this day at a slower rate, nearly 25 years later. An early evaluation of the water chemistry in the flooding mines suggested that the initially poor water quality was the result of flushing of a reservoir of stored acidity and metals. However, a detailed water balance for the Berkeley pit, underground workings, and associated mining features suggests an alternative explanation. During the early period of mine flooding, acidic surface water from the deactivated heap leach operations and nearby acid rock drainage were routed into the empty Berkeley Pit, and thence drained downward and outward into the underground mine workings, causing widespread degradation of water quality in the underlying workings. After 21 months, the hydraulic gradients in the system reversed, causing a change in the direction of ground water flow and a gradual improvement in water quality of the mine shafts.     

Reducing the Hardness of Mine Water Using Transformed Fly Ash

In the Jharia Coalfields, Dhanbad, India, huge quantities of water are pumped out of underground mines to make mining possible. The water contains high concentrations of total hardness, which makes it unsuitable for domestic use. Waste fly ash generated nearby from burning the coal in thermal power plants can be converted into a zeolitic mineral, and used to treat the mine water. The fly ash zeolite was determined to be effective in removing total hardness from the mine water. At a 40 g/L dose of fly ash zeolite, approximately 72% of the hardness was removed from the mine water. However, the mine water still requires additional treatment to further reduce total dissolved solids to make the mine water potable.     

应用于金属矿山地下热水源的热泵换热系统设计

以充分利用金属矿山地下开采过程中涌出的热水能源为目的,分析了鲁东地区地下热水能量的来源,指出地热水在矿山应用的途径和方法,分析热泵在矿山应用的优势。介绍了青岛市某金属矿山井下热水概况,根据矿山现状设计了热泵换热系统,将其用于矿山附近建筑物室内采暖,该方法比用煤炭取暖节省33%的成本。     

The differences in underground mines dewatering with the application of caving or backfilling mining methods

Zambia Consolidated Copper Mines Ltd. (ZCCM) is planning a substantial increase in ore production in several of their underground mines on the Zambian Copperbelt over the next 10 years. The future production strategy is based on development of productive and economic mining methods through the application of mechanization and backfilling. Mechanization is designed to provide the production capability and the backfilling is designed to reduce water inflow into the mines. A similar trend can be seen in world-wide changes in mining methods from open stoping and sub-level caving to cut-and-fill stoping. Backfill is being employed worldwide, including in Australia, Canada, Sweden, Latin America, Zambia, and the U.S.A. Plans for backfill mining methods are underway for future operations in Chile, Canada, Zambia, and Mexico. The principal reasons for these changes in mining methods are twofold:

? Increased ore recovery, and

? Decreased environmental impact.

The main difference in the environmental impacts between mining with sub-level caving or open stoping and mining with backfilling methods is the reduction in subsidence or the potential for subsidence. Backfilling reduces ground movements in the rock overlying and adjacent to mine openings as well as subsidence at the surface. Reduced ground movement decreases the number and size of fracture-controlled hydraulic flow paths into a mine and, thereby, the impact of mining on surface and ground water resources. This paper deals with: 1) The impacts caused by open stoping and sub-level caving in comparison to backfilling methods; 2) The approximate impact of backfill on dewatering strategies, and; 3) The environmental benefits of backfill mining. The differences in mine drainage strategies are supported by case histories from various mines.     

Technology of mine water control in China

The mines of the Permo-Carboniferous coalfield in North China and the Late Permian coalfield in the South are seriously threatened with Karst Water from limestone, which results in frequent water inrush and mine inundation. The mines in the areas of the Yellow Huai and Shongliao plains are generally endangered by the water from Quarternary alluvium. Therefore, groundwater disaster is one of the main problems of coal mine safety in China. After liberation, a great deal of research work on protecting against mine water has been done under the direction of the Ministry of Coal Industry. Successful results have been obtained in respects of studies of mine water inrush mechanisms, dewatering and depression of aquifer, sealing water inrush spots by grouting and cutting-off water flow by cement grout curtains, protecting against water at ground and underground as well as investigating the hydrogeological conditions in a mine area and calculating the mine inflow. Many practical problems in coal production have been solved, and the theory and technology of mine water control with China's typical features, have gradually been formed. However, further study and solution of some problems will be required because the hydrogeological conditions of the coalfields in China are extremely complicated.     

基于MSPS系统和FLAC3D软件的地下开采地表沉陷预测分析

地下开采可能诱发地面建(构)筑物变形及地表环境破坏,造成巨大损失。为研究地下开采后能否消除对地表建(构)筑物的安全影响,以拟采用充填采矿法开采的某金矿为工程背景,依据地下开采地表沉陷理论,运用MSPS和FLAC_^3D相结合的方法,对充填开采后地表沉陷进行预测分析与对比印证,确定矿区充填开采后地面沉陷范围与大小。预测分析结果表明：该矿采用充填法开采,并采取合理的安全对策后,由地下开采所诱发的地面沉陷变量均未超过地面保护对象的地表允许变形值,满足建(构)筑物保护等级的要求;MSPS系统预测的地表最大下沉值偏大,而FLAC_^3D软件预测的地表最大下沉值较小,可能与数值模拟岩体力学参数取值有关,两种方法预测的地表最大下沉值都在允许变形范围内。分析结果对该矿安全设施设计以及类似矿山地表稳定性分析具有参考价值。     

A new method of mine drainage prediction using unit static resource method

The paper considers mine drainage prediction in a partially closed mine with a fractured karst aquifer which is highly permeable and quite thick. The aquifer is bordered along the edge of the mine by impermeable boundaries and zones, of low transmissibility. Inside the mine there are significant quantities of static resource ground water. However, the extent of ground water outside the mine is relatively less. In such a mine, a series of characteristics can be observed to accompany the pumpage when the pumped discharge exceeds the ground water recharge. It is rather difficult to predict the drainage of such a mine, owing to the unsteady drawdown of the ground water level, and the complicated boundary conditions. In addition there is difficulty in measuring the hydrogeological parameters such as the permeability coefficient of the aquifer, etc. Quoting the concept of “unit static resource” that has been well defined previously, this paper offers a new type of “unit static resource method”. It was developed in 1972 and has been effectively applied to drainage prediction problems at several mines in the northern part of China. The method is applicable not only to partially closed mines but also to completely closed ones, and furthermore, includes the earlier “unit static resource method”. It can be used to appreciate water supply besides predicting mine drainage.     

铜录山矿帷幕注浆堵水技术

铜录山铜矿是露天与地下联合开采的大型铜矿。由于开采期间排水疏干引起地表大面积塌陷,大量地表水灌入井下,严重威胁井下生产安全。为此决定采用帷幕注浆方法以截流地下水和防止地面塌陷。帷幕注浆工程在可行性研究的基础上进行的,历时4年半。工程完工后对注浆效果进行了评价,结果表明,堵水效果达62％,减少了井下及露天坑的排水量;幕内外出现明显水位差(38m左右),幕外水位回升,控制了地面的塌陷。给矿山创造经济效益4000万元左右。     

A phased approach to mine dewatering

The construction of an excavation often means penetrating the local or regional water table. This causes inflows, which if the country rock is significantly permeable can become at best a nuisance to operations and at worst a hazard. Dry working conditions are preferable as they reduce wear and tear on machinery, reduce earth moving costs and often improve slope stability and therefore safety. Options available to mine management are dewatering, diversion, sealing or a combination of methods. To achieve the most effective, least cost method it is essential that the origin of the ground water is determined. The success of a dewatering exercise is directly linked to an understanding of the ground water regime. Mines cannot afford to use “blanket methods” when dealing with ground water. It is essential to target the actual inflows and not divert or seal off water indiscriminately. The potential impact of ground water inflow to a mine can often be assessed at the pre feasibility stage. A hydrogeological investigation is best tackled in three phases. The first phase is a desk study and borehole census and can be initiated by the mine or quarry developers. The main objective is to determine water levels and regional hydrogeology. It is very important that the Phase one hydrogeological investigation is started at the same time as the geological investigation. All exploration drilling records should include comment on where water was encountered and in what volume. The objective of Phase two is to indicate at a first level of confidence the probable impact of mining on the ground water and vice versa. The level of confidence is determined by the quality of data collected in Phase one. At the end of Phase one management will be able to assess if water is going to prove a hazard to mining or not. If it is going to be a hazard then Phase three will be activated. The objective of Phase three is to plan how to reduce or remove the hazard and either handle or divert the probable inflows. Phase three can be accomplished through trial dewatering, computer modelling or through the application of practical experience. The level of sophistication at Phase three is determined by the potential costs and risks involved.     

Dewatering concepts at Zambian Copperbelt Mines

During the financial year 1992/93, Zambian Consolidated Copper Mines Ltd (ZCCM) Ltd pumped a total of 263 million tonnes of water from its various mining operations. During the same period the Company produced 23 million tonnes of ore, giving a water to ore ratio of 11.4 tonnes of water per tonne of ore produced. Hydrostatic pressures interesected in underground boreholes ranged upto about 5MPa. Against this background the dewatering techniques that have been practised on the Copperbelt at ZCCM’s mines are reviewed. The methods include the surface exclusion of water, interception of water, simple drainage, breakthrough methods, dewatering drilling, grouting isotope analysis and computer modelling. The surface exclusion of water includes the use of canals and pipelines to carry water over hydrological hazard zones, herringbone ditches to speed up run-off, stream gauging to locate hydrological hazard zones and weirs to quantify flow rates, and the judicious geological siting of dams and other surface water structures. Interception methods basically revolve around the concept of interception of the potential mine drainage at the extremities of the mines in order to ensure that the cone of dewatering is lowered before it intercepts the main mining areas. Simple drainage is the mining of drives into aquifers at reduced hydrostatic pressures in order to drain specific aquifers. Breakthrough methods also involve the mining of drives into aquifers but in a more controlled manner than in simple drainage. In this instance drives are mined directly into aquifers utilising watertight doors or puddle pipes to protect the main mine workings. Dewatering drilling is the most widely used method of dewatering used on the Copperbelt. It may be conveniently divided into surface and underground dewatering boreholes. Surface dewatering boreholes may be either pumped, utilising borehole pumps, used for piezometric measurements, or used in open pit situations to drain aquifers under hydrostatic pressure. Underground dewatering boreholes are the most widely practised method of dewatering on the Copperbelt and involve the drilling of boreholes into aquifers, in order to lower the hydrostatic head in a particular aquifer. A number of different techniques are discussed. Grouting to exclude the inflow of water into mines has long been known as a method of groundwater exclusion. The uses of cementious grouts and resin grouts are discussed. Isotope analysis has been used at Konkola Division to give indications of both the age and possible origins of the Konkola groundwaters. Computer modelling utilising modflow software has been used at Konkola Division to predict drawdown of the hydrostatic head in a number of different mining scenarios. A changeover from caving mining methods to mining methods involving the use of backfill should permit certain mines to effect major cost savings with regard to dewatering costs. The implications of this change in mining methods is discussed. Environmental aspects of mine drainage from ZCCM’s mines is addressed and the lack of an acid mine drainage problem briefly discussed.     

Delineating the Origin of Groundwater in the Golgohar Mine Area of Iran Using Stable Isotopes of <Superscript>2</Superscript>H and <Superscript>18</Superscript>O and Hydrochemistry

The Golgohar iron ore mine in southern Iran is a large open pit that uses dewatering (≈4000–5000 m³/day) to prevent flooding. A vast cone of depression has formed, and water from a large area flows into the pit. A study of the different sources of this water was necessary to plan a proper dewatering project. Moreover, the discharged water is saline and contains high levels of contaminants. Based on hydrochemical and isotope (¹⁸O and ²H) analysis, it was concluded that the area’s deep saline groundwater is coming from the Sirjan (Kheirabad) salt playa (north of the mine) by saltwater intrusion while the chemistry of more distant groundwater was due to dissolved minerals.     

Causes and Effects of Uncontrolled Water Inrush into a Decommissioned Mine Shaft

Central Europe experienced catastrophic rainfalls and flooding in 2010. This paper discusses a decommissioned shaft that was flooded by surface water, which led to displacement of shaft backfill and an inrush of large amounts of water into an underground pumping station. The weather conditions for the period preceding the inrush, the hydrogeological conditions, the quantity of water that entered the mine dewatering systems, and the underground hydraulic connections are all described. Uncontrolled inflow of water as a cause of backfill saturation and the hazard for active underground infrastructure were analysed. A need to rebuild damaged infrastructure was identified. The case study highlights the need to improve underground mine closure requirements to ensure safe conditions above ground, particularly in densely populated areas.     

井下泵房自动化控制系统的应用

在地下矿山开采中,井下排水系统对地下矿山的安全生产至关重要,由于井下矿山排水系统仍大部分采用人工操作为主,劳动强度大和效率低,给井下排水带来一定的困难。为克服上述矿山生产问题,通过对矿山井下泵房进行自动化改造,并对水泵运行和水位监测、维护保养和节能等方面自动化控制系统进行优化。通过近2 a的运行,确保井下泵房实现运行高效、安全可靠。