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1.
The environmental performance of cemented paste backfill (CPB; a mixture of tailings, water and binder), which contains sulphide mineral-bearing tailings, is strongly influenced by its reactivity. However, our understanding of the reactivity of CPB under various thermal loading conditions as well as its evolution with time is limited. Hence, a laboratory investigation is conducted to study the effects of curing and ambient (atmospheric) temperatures on the reactivity of CPB. Oxygen consumption (OC) tests are conducted on CPB specimens cured at different temperatures to study their reactivity. Furthermore, microstructural analyses (e.g., x-ray diffraction (XRD), mercury intrusion porosimetry, and thermogravimetry/derivative thermogravimetry) are performed to assess the microstructural characteristics of the tested CPBs. The results show that the reactivity of CPB is temperature-dependent. As the curing temperature increases, the reactivity generally decreases. The reactivity is also affected by the ambient temperature. The reactivity increases as the atmospheric temperature increases. However, the extent of the effect of the temperature depends on the curing time and is generally more pronounced at the early ages. Furthermore, the presence of sulphate in the pore water of CPB can significantly affect the reactivity of CPB cured at high temperatures (50 °C). The findings of this study will therefore help to better assess and predict the environmental behavior of CPB under various field thermal conditions. 相似文献
2.
The shear stress–strain behaviour and shear strength parameters of the interface between cemented paste backfill (CPB) and rock are of practical importance in the optimal and safe design of CPB structures. An understanding of the shear behaviour and properties at this interface is also required to develop comprehensive interface models for CPB-rock analyses, interface design methods for the static and dynamic stability analysis of CPB structures, and building high performance CPB structures. In this study, direct shear tests were conducted to investigate the interface shear strength behaviour between CPB and rock. All tests were carried out in a standard direct shear test apparatus for a range of curing ages of 1 to 28 days for the CPB. The procedures of the laboratory tests will be described. Results will be presented for interface shear behaviour, including stress–strain curves, vertical deformation and shear strength parameters. The test results show that the shear strength parameters and behaviour of the CPB-rock interface are time-dependent and significantly influenced by the normal load. 相似文献
3.
Alireza Ghirian 《Geomechanics and Geoengineering》2016,11(4):237-251
A pressure cell apparatus has been developed in this research work to study the long-term hydro-mechanical behaviour of cemented paste backfill (CPB) cured under applied stress. The samples are cured for 7, 28, 90 and 150 days and the evolution of their mechanical, hydraulic, physical and microstructural properties is studied. Also, the suction, temperature and electrical conductivity are monitored for a period of 150 days of curing. The testing and monitoring programmes are conducted in undrained conditions, with and without pressure application. The obtained results show that the curing stress affects the hydro-mechanical behaviour of CPB for up to 28 days. Within this curing period, the CPB exhibits enhanced hydro-mechanical performance. However, application of sustained excessive curing stress onto the CPB samples induces the propagation of microcracks in the backfill structure, thus causing lower mechanical strength and higher fluid permeability at the more advanced ages. Furthermore, the mineralogical and chemical compositions of the tailings (e.g., sulfidic tailings) can significantly alter the mechanical strength properties (uniaxial compressive strength and elastic modulus) and the permeability of the CPB. The evolution of coupled factors and characteristics of the CPB at an early age control and influence its long-term behaviour and performance. 相似文献
4.
Cemented paste backfill (CPB) is a mixture of dewatered tailings, hydraulic binders and water. In addition to contributing to the stability of mine workplaces, CPB greatly benefits the environment by minimizing surface tailings disposal. Hence, it has become one of the most commonly used ways in mine backfilling around the world. Temperature can significantly affect the mechanical properties of cemented backfill. A source of heat in CPB is produced by binder hydration. Hence, a FLAC based numerical model is developed to predict and analyse the heat developed by hydrating CPB structures. To validate the model, results of the developed model are compared with three case studies (mathematical, laboratory, and field investigations). The validation results show a good agreement between the developed model and these cases. The effects of stope geometry, thermal properties of both rock and CPB, filling rate, binder content and initial boundary conditions are also investigated. 相似文献
5.
Unsaturated hydraulic properties of cemented tailings backfill that contains sodium silicate 总被引:2,自引:0,他引:2
Recycling the mine waste (tailings) into cemented tailings backfill has economical and environmental advantages for the mining industry. One of the most recent types of cemented tailings backfill is gelfill (GF), a backfill that contains sodium silicate as chemical additive. GF is typically made of tailings, water, binder and chemical additives (sodium silicate gel). It is a promising mine tailings backfill technology. From a design point of view, the environmental performance or durability of GF structures is considered as a key factor. Due to the fact that GF structures are cementitious tailings, their durability and environmental performance depend on their ability to resist the flow of aggressive elements (water and oxygen). Thus, understanding the unsaturated hydraulic properties of GF is essential for a cost-effective, environmentally friendly and durable design of GF structures. However, there is a lack of information with regards to unsaturated hydraulic properties of GF, the factors that affect them and their evolution with time. Hence, the unsaturated hydraulic properties (water retention curve (WRC) or water characteristic curve, air entry value (AEV), residual water content, unsaturated hydraulic conductivity) of GF are investigated in this paper. GF samples of various compositions and cured in room temperature for different times (3, 7, 28, and 90 days) are considered. Saturated hydraulic conductivity and microstructural tests have been conducted; WRCs are measured by using a WP4-T dewpoint potentiameter and the saline solution method. Unsaturated hydraulic conductivity is predicted using the van Genuchten (1980) equation. The water retention curve (WRC) is determined as the relationship between volumetric water content and suction for each GF mix and curing time. The van Genuchten (1980) equation is used to simulate the WRC to best-fit the experimental data. AEV and residual water content are also computed for each mix and curing time. Furthermore, functions are developed to predict the evolution of AEVs, residual water content and fitting parameters of the van Genuchten model with degree of hydration. Important outcomes have been achieved with regards to unsaturated hydraulic properties. The unsaturated hydraulic conductivity of GF was calculated to decrease when the suction, binder content, and degree of hydration increase. The effects of binder content and degree of hydration are more obvious at low suction ranges. The obtained results would contribute to a better design and assessment of the durability and environmental performance of GF structures. 相似文献
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7.
Role of carbonates in mitigation of metal release from mining waste. Evidence from humidity cells tests 总被引:7,自引:0,他引:7
Leaching of two contrasting types of sulphidic tailings in humidity cells has been performed. The release of heavy metals
and the oxidation rate have been studied. Tailings from the Laver mine contain a few percent sulphides and lack carbonates,
whereas tailings from the Stekenjokk mine are both sulphide- and carbonate-rich. The results showed that in the leachates
from the Laver samples, the metal concentrations increased and pH decreased with time, indicating an increased oxidation rate.
In the Stekenjokk samples, pH remained high during the experiment, thereby keeping the metal concentrations low in the leachates.
The oxidation rate also decreased with time, probably due to Fe-hydroxide coatings on sulphide surfaces. The results show
that addition of carbonates and the maintenance of a high pH not only reduce the solubility of heavy metals, but also decrease
the oxidation rate of sulphides.
Received: 20 January 1998 · Accepted: 2 April 1998 相似文献
8.
Mobility and retention of trace elements in hardpan-cemented cassiterite tailings, north Queensland, Australia 总被引:1,自引:0,他引:1
This study reports on the mobility and retention of trace elements in cassiterite tailings at the inactive Jumna mill, tropical north Queensland. Since the 1980s, the uncapped tailings have developed laterally discontinuous Fe-rich hardpans, which are located in the higher parts of gently sloping tailings masses and at the top (<50 cm) of the tailings piles. Hardpan-cemented tailings comprise thin layers (typically ∼0.2–2 mm thick) of HFO (hydrous ferric oxides) and sulfate efflorescences cementing tailings grains. In comparison to the tailings, the hardpan-cemented tailings contain significantly higher median As, Ca, Cd, Co, Cu, Fe, In, Mn, Mo, Stotal, Th, U, Y and Zn values. Partial leaching studies of tailings and pond water analyses indicate that wetting and acidification of Fe-cemented tailings removes significant proportions of trace elements into pore and surface waters. Tin shows no mobility due to the presence of weathering-resistant cassiterite (SnO2) and, As and Pb display limited mobility possibly due to their coprecipitation with jarosite-type phases and HFO materials at the top of the tailings profile. By contrast, the trace elements Cd, Ce, Cu, La, Ni, Pb, U and Zn display the greatest mobility, possibly due to their incorporation in soluble sulfate efflorescences and sorption onto mineral and HFO surfaces. Hence, the Fe-rich hardpans do not protect the sulfidic tailings from further oxidation nor do they cause permanent sequestration of trace elements. 相似文献
9.
This study develops a three-dimensional heterogeneous numerical model to simulate the water inrush process and predict the water yield for mineral exploration in Yangzhuang Iron Mine in Anhui Province. To identify the hydrogeological parameters of the aquifer in the study area, the model was calibrated and validated using the observed heads through the integrated trial-and-error and automated techniques. Also, the sensitivity analysis of the model was performed to evaluate the uncertainty associated with the calibrated model. According to the mine construction plan at different mining levels of -500 m, -600 m, and -700 m, the calibrated model was then applied to predict the water yields dependent on the different mining levels. As indicated by the prediction results, the numerical simulation model can systematically describe the groundwater system in the mining area and determine the source of water inrush in this iron mine. In conclusion, numerical analyses carried out in this study can provide guidance to decision-makers in balancing the iron ore mining and mine dewatering in the future. 相似文献
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After placement of cemented tailings backfill (CTB), which is a mixture of tailings (man‐made soil), water, and binder, into underground mined‐out voids (stopes), the hydration reaction of the binder converts the capillary water into chemically bound water, which results in the reduction of the water content in the pores of the CTB, thereby causing a reduction in the pore‐water pressure in the CTB (self‐desiccation). Self‐desiccation has a significant impact on the pore‐water pressure and effective stress development in CTB and paramount and practical importance for the stability assessment and design of CTB structures and barricades. However, self‐desiccation in CTB structures is complex because it is a function of the multiphysics or coupled (i.e., thermal, hydraulic, mechanical, and chemical) processes that occur in CTB. To understand the self‐desiccation behavior of CTB, an integrated multiphysics model of self‐desiccation is developed in this study, which fully considers the coupled thermal, hydraulic, mechanical, and chemical processes and the consolidation process in CTB. All model coefficients are determined in measurable parameters. Moreover, the predictive ability of the model is verified with extensive case studies. A series of engineering issues are examined with the validated model to investigate the self‐desiccation process in CTB structures with respect to the changes in the mixture recipe, backfilling, and the surrounding rock and curing conditions. The obtained results provide in‐depth insight into the self‐desiccation behavior of CTB structures. The developed multiphysics model is therefore a potential tool for assessing and predicting self‐desiccation in CTB structures. 相似文献
12.
Acid mine drainage is a major source of water pollution in the Sarcheshmeh porphyry copper mine area. The concentrations of heavy metals and rare earth elements (REEs) in the host rocks, natural waters and acid mine drainage (AMD) associated with mining and tailing impoundments are determined. Contrary to the solid samples, AMDs and impacted stream waters are enriched in middle rare earth elements (MREEs) and heavy rare earth elements (HREEs) relative to light rare earth elements (LREEs). This behavior suggests that REE probably fractionate during sulfide oxidation and acid generation and subsequent transport, so that MREE and HREE are preferentially enriched. Speciation modeling predict that the dominant dissolved REE inorganic species are Ln3+, Ln(SO4)2−, LnSO4+, LnHCO32+, Ln(CO3)2− and LnCO3+. Compared to natural waters, Sarcheshmeh AMD is enriched in REEs and SO42−. High concentrations of SO42− lead to the formation of stable LnSO4+, thereby resulting in higher concentrations of REEs in AMD samples. The model indicates that LnSO4+ is the dissolved form of REE in acid waters, while carbonate and dicarbonate complexes are the most abundant dissolved REE species in alkaline waters. The speciation calculations indicate that other factors besides complexation of the REE's, such as release of MREE from dissolution and/or desorption processes in soluble salts and poorly crystalline iron oxyhydroxy sulfates as well as dissolution of host rock MREE-bearing minerals control the dissolved REE concentrations and, hence, the MREE-enriched patterns of acid mine waters. 相似文献
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14.
Time-of-flight laser-ionization mass spectrometry was applied to study the chemical composition of mineral particle surfaces
in a sulphide-rich mine-tailings impoundment. This surface-sensitive technique provides chemical information from surfaces
of irregularly shaped mineral particles (both conductive and insulators) less than 100 μm in diameter, which are considered
to be representative of particle surface coatings in the tailings pile (after drying). In addition, depth profiles in the
mineral particles were obtained. The combination of speed of analysis (1 min), small beam-diameter (2–4 μm), surface sensitivity
(2–10 nm), trace-element sensitivity, and capability to analyze rough surfaces makes this method useful as a complement to
studies of pore-water geochemistry and tailings mineralogy. As an example, the behavior of Pb and As in the Kidd Creek tailings
dam near Timmins, Ontario, Canada, was studied, using a combination of surface analyses, and pore-water geochemical data.
Received: 22 February 1995 / Accepted: 6 January 1996 相似文献
15.
矿山三维立体模型的建立是矿山数字化的基础。本文系统收集了阳山金矿安坝矿段勘探线剖面图28条,编录了钻孔数据106个,分析了31446个钻孔采样结果,建立了钻孔数据库;应用3D Mine矿业工程软件构建了地形模型和矿体模型;对于三维建模的一般技术路线进行了初步归纳;建立了安坝矿段三维实体模型;并对矿体形态进行了分析,从而探讨了阳山金矿区的构造控矿规律,解释了矿体形态可能的形成原因,以期为阳山的深入找矿工作提供一定的理论依据。 相似文献
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17.
The effects of stress/deformation on fluid flow and contaminant transport in fractured rocks is one of the major concerns for performance and safety assessments of many subsurface engineering problems, especially radioactive waste disposal and oil/gas reservoir fields. However, very little progress has been made to study this issue due to difficulties in both experiments and numerical modeling. The objective of this study is to systematically investigate the influence of stress on solute transport in fractured rocks for the first time, considering different stress and hydraulic pressure conditions. A hybrid approach combining discrete element method (DEM) for stress-flow simulations and a particle tracking algorithm is developed. The impact of matrix diffusion (diffusion of molecular size solutes in and out of the rock matrix, and sorption onto the surface of micropores in rock matrix) is also included. The numerical results show that stress not only significantly changes the solute residence time through the fracture networks, but also changes the solute travel paths. Matrix diffusion plays a dominant role in solute transport when the hydraulic gradient is small, which is often encountered in practice. 相似文献
18.
Xian-Huan Wen J. Jaime Gómez-Hernandez José E. Capilla Andrés Sahuquillo 《Mathematical Geology》1996,28(7):951-968
Transmissivity and head data are sampled from an exhaustive synthetic reference field and used to predict the arrival positions and arrival times of a number of particles transported across the field, together with an uncertainty estimate. Different combinations of number of transmissivity data and number of head data used are considered in each one of a series of 64 Monte-Carlo analyses. In each analysis, 250 realizations of transmissivity fields conditioned to both transmissivity and head data are generated using a novel geostatistically based inverse method. Pooling the solutions of the flow and transport equations in all 250 realizations allows building conditional frequency distributions for particle arrival positions and arrival times. By comparing these fresquency distributions, we can assess the incremental gain that additional head data provide. The main conclusion is that the first few head data dramatically improve the quality of transport predictions. 相似文献
19.
地质系统热-水-力耦合作用的随机建模初步研究 总被引:2,自引:0,他引:2
热-水-力(THM)耦合作用是岩石力学与环境地质中的重要基础理论问题,核废料地质处置库周围的缓冲材料和围岩中的热-水-力耦合现象将影响其力学稳定性、热传导性和渗透性,进而影响放射性核素在裂隙岩体中的迁移规律。核废料或放射性废料的地下深埋处置是国际上正在研究的永久性隔离的有效方法之一。因此,对核废料地质处置法安全性评估的一个重要内容就是对裂隙岩体中力学稳定性与构造应力、地下水渗流及热载荷等的耦合作用之数值模拟和评估。这已成为当前刻不容缓的重要的环境影响评价课题。笔者研究了温度场-渗流场-应力场中热传导系数和渗透率以及岩体力学参数的空间变异性,用实验方法研究三场耦合效应及裂隙岩体的场性能等效处理,试图建立热-水-力耦合作用的随机性数学模型及可视化数值模拟方法,为核废料地质处置安全性评估提供直观的新方法。 相似文献
20.
Hybrid analytical and finite element numerical modeling of mass and heat transport in fractured rocks with matrix diffusion 总被引:1,自引:0,他引:1
Christopher I. McDermott Robert Walsh Ralph Mettier Georg Kosakowski Olaf Kolditz 《Computational Geosciences》2009,13(3):349-361
Quantification of mass and heat transport in fractured porous rocks is important to areas such as contaminant transport, storage
and release in fractured rock aquifers, the migration and sorption of radioactive nuclides from waste depositories, and the
characterization of engineered heat exchangers in the context of enhanced geothermal systems. The large difference between
flow and transport characteristics in fractures and in the surrounding matrix rock means models of such systems are forced
to make a number of simplifications. Analytical approaches assume a homogeneous system, numerical approaches address the scale
at which a process is operating, but may lose individual important processes due to averaging considerations. Numerical stability
criteria limit the contrasts possible in defining material properties. Here, a hybrid analytical–numerical method for transport
modeling in fractured media is presented. This method combines a numerical model for flow and transport in a heterogeneous
fracture and an analytical solution for matrix diffusion. By linking the two types of model, the advantages of both methods
can be combined. The methodology as well as the mathematical background are developed, verified for simple geometries, and
applied to fractures representing experimental field conditions in the Grimsel rock laboratory. 相似文献