A Simple Analytical Model for Interpretation of Tracer Tests in Two-Domain Subsurface Flow Systems

Abstract.   Two-domain subsurface flow systems are common in nature and in engineered wetlands and similar passive treatment systems. To expedite analysis of flow and solute transport processes in such systems, a simple mathematical model for one-dimensional flow and transport in such systems has been derived by combining separate analytical solutions for the partial differential equations that describe (i) straight-forward transport (by advection and mechanical mixing only) in a rapid-flow domain of large pores, and (ii) transport in a similar system that is in intimate contact with an essentially stagnant micro-porous domain, with which it exchanges solutes solely by molecular diffusion. Two tracer tests were performed in passive mine water treatment systems that were anticipated to comprise coupled fast and stagnant porous domains. Application of the new analytical model readily yielded breakthrough curves very similar to those observed. Besides providing corroboration of the two-domain concept as an explanation for solute transport in these passive treatment systems, the new model yields a fractionation coefficient, which may be a useful objective index of the modal hydraulic behaviour of natural and man-made subsurface flow systems.     

A Bauxsol™-based Permeable Reactive Barrier for the Treatment of Acid Rock Drainage

Abstract.   Permeable reactive barriers (PRBs) have generally been used to treat low flow and/or low contaminant loads of acid rock drainage (ARD). Bauxsol, a product made from seawater-neutralized red mud (a by-product of alumina refining) buffers pH at 8.8 and has been shown to remove >99% of heavy metals loadings at >1000 meq/kg, which would make it an ideal medium for PRBs. Unfortunately, Bauxsol is very fine-grained (>90% of the material <10 µm) and therefore, possesses a very low hydraulic conductivity. Consequently, sand/Bauxsol mixtures were trialed to determine hydraulic conductivity and ARD treatment capacities. Column tests indicated that the sand/Bauxsol mixtures maintain a higher hydraulic conductivity when used to treat ARD than when used with tap water. A 75:25 sand: Bauxsol filter with a 130 mm thick layer of reactive media had a hydraulic conductivity of 3.06 x 10^-5 m/s and except for Al, treated a highly contaminated ARD to ANZECC (2000) drinking water guidelines. A field trial of a 1 m³ PRB (70:30 sand:Bauxsol mixture) with a hydraulic conductivity of 9.8 x 10^-5 m/s treated about 45,000 L of highly contaminated ARD to the ANZECC (2000) drinking water standards, and about 27,000 L of this water had heavy metal loadings reduced to the ANZECC (2000) Protection of Aquatic Ecosystem guideline of >90% species protection.The metal binding preference of Cu>Pb>Zn>Mn displayed by the PRB is consistent with the pKa of hydration values and it appears that MOH⁺ formation dominates the removal of these metals. However, other removal processes appear to apply for Fe, Al, and Cd. Overall metal removal efficiencies ranged from 91.22% for Mn to >99.99% for Cu. Analysis of dried spent Bauxsol indicates that bound metals are not readily leachable, allowing the spent media to be disposed safely in a landfill.     

Mine Water Literature in ISI’s Science Citation Index Expanded™

Abstract.   Scientists in most countries are assessed by the number of papers published in journals that are cited in the Science Citation index. This article reviews the mine water related entries in the Science Citation Index Expanded and discusses the results. Mine water relevant literature is spread over more than 900 journals, with 13 of them accounting for 25% of all relevant papers. No journal focused on mine water relevant issues can be found in the Index.     

The Influence of Coal Quality Variation on Utilization of Water from Abandoned Coal Mines as a Municipal Water Source

Abstract.   As population increases and high quality water becomes more difficult to obtain, many communities will seek alternative water supply sources. Some municipalities have realized that they have a reservoir of unexploited water readily available in abandoned underground coal mines. Analysis of the mines history, the quality of the coal and water that reside within the mine, and knowledge of local hydrology, geology, and mine chemistry will provide communities with the information they need to determine the best mine sites to use.     

A Tragic Disaster Caused by the Failure of Tailings Dams Leads to the Formation of the Stava 1985 Foundation

Abstract.   This paper summarizes the dynamics and causes of the Stava disaster, and highlights some risky design procedures that led to the 19 July 1985 tailings dam failure. It then presents the Stava 1985 Foundation, which was formed to focus attention on such risks and to strengthen the culture of respect for human lives and safety.     

Pietra Serena Mining in Fiesole. Part I: Historical, Cultural, and Cognitive Aspects

Within comprehensive investigation of Fiesole area (Italy), scientific, technical, and cultural aspects are considered for mining and using the traditional Pietra Serena stone geologically known as quarry stone.     

Radionuclide Contamination of Surface Waters, Sediments, and Soil Caused by Coal Mining Activities in the ruhr District (Germany)

Abstract.   The discharge of highly mineralised mine waters with enhanced ²²⁶Ra and ²²⁸Ra activity concentrations has affected creeks, rivers, sediments, soils, and plants along the Lippe River and its tributaries. ²²⁶Ra activity concentrations were elevated in all water samples receiving mine water, with activity concentrations gradually decreasing with increased distance from the colliery due to dilution and chemical precipitation of radium with barium. Increased concentrations of radium and radium decay products were also measured in sediments and flood-affected soils. The sediments show an enrichment of ²²⁶Ra up to a factor of 750, while the contaminated soils only reach a factor of 10. In aquatic plants, a 4-fold increase in ²²⁶Ra activity concentrations was measured downstream of the discharge points. The contamination of the river banks and adjacent floodplain with radium is responsible for enhanced gamma dose rates, which, along with the incorporation of soil by playing children, provide potential radiation exposure to the public.     

Geomechanical Substantiation of the Parameters for Underground Mining of “Mir” Kimberlite Pipe

The change in the stress-strain state of ore mass and enclosing rocks on the transition from open to underground mining method in the Mir mine is estimated.     

Stress State of the Rock Mass in the Vicinity of Underground Mining Workings, Pit Edges, and below Its Bottom

An analysis is performed for the stress state of edges and bottom of the Aikhal/ open-pit mine. The influence exerted by the ratio of vertical and horizontal components of the initial stress-field on the results of numerical modeling of mining-technical situation in ceasing the open mining of kimberlite pipe is considered.     

Pietra Serena Mining in Fiesole. Part II: Geological Situation

The results are presented for the investigations into the geological estimate of Macigno formation representing an Oligocene-Miocene turbiditic sequence of the Northern Apennines, from the coarse-graded beds of which the Pietra Serena quarry stone was mined. It is shown that the sedimentological features, the physico-mechanical properties, and the mineralogical composition of rocks govern the distinctions in the operating performances.     

Stressed state of rocks of block structure

Conclusions 1. The stressed state of rock masses depends to a considerable extent on their block structure. There is no clear dependence for stresses on block geometric dimensions and shape.2. A block nature for the rock mass increases the proportion of the largest ratio of principal stresses ₂/₁ compared with a homogeneous rock mass at the same points. In other words in block masses the maximum tangential stresses are greater than in a homogeneous rock mass which promotes movement of blocks in relation to each other on a background of general equilibrium for a structure of a larger scale level.3. A block structure for rock mass promotes reorientation of the principal stresses compared with a homogeneous rock mass.Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 5, pp. 38–47, September–October, 1994.     

Optimizing the Effluent Treatment at a Coal Mine by Process Modelling

Abstract:   The water network of a coal mine was audited and simulated by an interactive steady state model and the results were used to optimise the mines water management strategy. Simulation of the interactions showed that calcium carbonate powder could be used as an alternative to lime for neutralization of acid water at a reagent cost saving of 56%. Gypsum crystallization would reduce sulphate concentrations in the neutralization plant by 30% and in the coal processing plant by 60%. The capital cost for a neutralization/gypsum crystallization plant for separate treatment of coal discard leachate and less polluted streams would cost 3.0 million Rand (R), compared to R10.3 million for combined treatment. Only slightly less (8.9 t/d vs. 9.5 t/d) sulphate removal would be achieved during separate treatment. The over-saturation index (OSI) value can be controlled effectively by removing sulphate from the feed water for coal processing. Sulphate has to be lowered to 350 mg/L in a flow of 222 m³/h to obtain an OSI value less than 1. The capital cost of a 222 m³/h biological sulphate removal plant was estimated at R21.8 million (R4.1 million/(ML/d)); the running cost was estimated at R13.7 million/a (R4.10/m³). Pre-washing of the coal would reduce capital and running costs.     

Monitoring the stress in a rock column on the basis of memory effects around a borehole

Conclusions Computer simulation shows that monitoring of the stress state of columns on the basis of emissional memory effects in the near-borehole rock requires a priori geological information on the orientation, dimensions, and density of the initial microcracks. Conditions for the interpretation of monitoring data are favorable in the presence of a system of initial microcracks oriented at an angle to the axis of the column, where 15°40° or 50°75°. The hydrosensor pressure P_gr obtained as a result of monitoring is directly proportional to the axial (vertical) stress in the column. The possibility of using this method in the case of random microcracking and in conditions when the crack system is oriented at = 0–15°, 40–50°, or 75–90° requires further — primarily experimental — investigation.Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 30–34, March–April, 1995.     

Problems of Nonlinear Geomechanics. Part II

The most important results are presented in complex for experimental and theoretical researches on nonlinear wave processes. It is shown that problems, concerning these processes, are governed for the most part by the phenomenon of the alternating-sign reaction of rocks to dynamic effects and the base characteristics of block-hierarchically modeled geomedia. Elements of the theory of deformation/ waves, which have made it possible to bring together a number of empirical relationships not previously explained within the framework of traditional theoretical concepts, are stated.     

Experimental Tests of a Multichannel Optoelectronic Longitudinal Deformometer

Test results are presented for a multichannel optoelectronic longitudinal deformometer MOED-1p at the Oktyabrsky/ mine of the Norilsk deposit with which rock strains and displacements were monitored around an observation working located in the area of a tectonic fault. Basic versions are developed for installing the transducers of the instrument with fixing of the datum-mark support both within the depth of the rock mass and also at the side wall of the working. A relationship is established between the designed technical and actual characteristics of the instrument.     

Geochemistry and Isotopic Composition of H2S-rich Water in Flooded Underground Mine Workings,Butte, Montana,USA

Abstract.   Groundwater being pumped from the flooded West Camp mine workings of Butte, Montana, is elevated in hydrogen sulfide (H₂S), has a circum-neutral pH, and has high arsenic but otherwise low metal concentrations. The daily flux of H₂S and As pumped from the extraction well are each estimated at roughly 0.1 kg. Isotopic analysis of coexisting aqueous sulfide and sulfate confirms that the H₂S was produced by bacterial sulfate reduction. the mine waters are close to equilibrium saturation with amorphous FeS, amorphous ZnS, siderite, rhodochrosite, calcite, and goethite, but are undersaturated with orpiment (As₂S₃). The higher solubility of orpiment relative to other mental sulfides allows concentrations of dissolved arsenic (~ 100 g/L) that are well above human health standards. The West Camp waters differ markedly from the acidic and heavy metal-rich mine waters of the nearby Berkeley pit-lake. These differences are partly attributed to geology, and partly to mining history.     

Leaching of gold from off-grade products

Kinetics of sulfide decomposition and gold dissolution during electrochemical extraction is described. The results are presented for the experiments on electrochemical extraction of gold from sulfide ores of the Kazakhstan deposits using sodium salt at the ABS Concern. The economically efficient parameters of applying leaching technology for rebellious sulfide ores are determined.Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 84–88, July–August, 2004.     

Effects of the complex loading of diabase

Condusions An experimental investigation of the dilatant properties of rock was conducted under a simple proportional loading right up to failure with determination of characteristics of the three-dimensional strength chart, as well as for its complex cyclic loading formulated from piecewise-linear segments of the path of a proportional load (or deformation) increment and partial unloading with measurement of the components of the tensor of strains, which are equal to those of the assigned stress tensor.It is established that dilatancy has different signs, depending on the type of complex stress state: all components of the strain tensor were compressive under pure shear, while one or two of the components of the strain tensor were obtained as tensile components for other ratios of stress-tensor components.Volume changes during plastic deformation appeared with the specimens subjected to a complex cyclic loading, when there is no similitude between the deviators of the stress and strain tensors. Under a complex cyclic loading, the passage of rock through a state of pure shear yields a consolidating effect, especially if the component of the stress or strain increment has the same Lodei—Nadai parameter during unloading (µ=0).It is established that maximum rock strength is attained in a state of pure shear with a higher hydrostatic component of the stress ternsor (under generalized shear).The author is deeply grateful to Academician of the Academy of Mining Sciences, Doctor of Physical and Mathematical Sciences, V. N. Oparin, for his discussion of the study and valuable comments and suggestions.The study was conducted with the financial support of the Russian Foundation for Fundamental Research (Grant 93-05-08643).Translated from Fizikotekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 5, pp. 45–52, September–October, 1996.     

On Hydrogeomechanical Causes of Accident in the Subway of Saint Petersburg

A scheme is developed for the deformation of tunnels in the Lesnaya - Muzhestvo Square station-to-station block of Saint Petersburg subway during incipience of accident in 1995. It is shown that the main cause of the repeated accident in the washout section was the rise of level of submorainic water-bearing horizon waters. The tunnels supporting soil massif reinforced by freezing column pipes were subjected to additional bending load, which resulted in cracks appearing in the tunnel lining.     

Stress State of Ore Mass in the Ascending Slice Mining System

An analysis is performed for the distribution of stresses in the elements of slicing system in mining the Internatsionalnaya kimberlite pipe. The parameters and conditions of carrying out the stoping operations in experimental-industrial block by ascending slices are substantiated.