某上游式尾矿坝安全性评价方法分析研究

尾矿库安全性评价在尾矿库运行中是一项至关重要的工作。本文借助实际的工程实例,使用规范规定的计算方法和公式,结合工程力学和流体力学基础理论知识,深入的研究了尾矿库坝坡稳定性和尾矿渗流稳定性的评价方法和计算过程,对现有的尾矿库安全性进行了评价。同时,通过实验室重塑性试验取得了为矿体的各项参数,应用二维边坡稳定性和渗流稳定性计算软件对尾矿库的稳定性进行了计算,对比解析法和数值法计算结果的异同,分析了产生差异的原因,为尾矿库安全性评价工作提供了一些借鉴。     

Groundwater pollution due to a tailings dam

In 1982, the Oman Mining Company (OMC) commenced copper mining and smelting operations in the area of Sohar (Wadi Suq), Sultanate of Oman. Seawater was used for mining operations until 1993. During this period, 11 million tonnes of tailings had been deposited behind an unlined tailings dam. This has resulted in a major groundwater pollution problem.

This paper presents results from investigation of groundwater pollution. Data pertaining to various parameters such as pH and TDS were obtained from the OMC. Most of the data were for a period of 12 years since 1984 and were gathered from an extensive network of field monitoring wells covering a distance of 14 km downstream of the tailings dam. The trends of groundwater pollution are presented with explanation. The issue of the existing remedial measures (cut-off trench for containment of the pollution source) is addressed briefly.     

Laboratory study of the clogging process and factors affecting clogging in a tailings dam

Laboratory simulation of clogging in the Lixi tailings dam (Shaanxi Province, China) is urgently required because clogging is an important factor affecting the dam stability. This work firstly presents the results of ferrous iron oxidation experiments using buffer solution. The results indicate that the ferrous iron oxidation follows first order kinetics, and the oxidation process is strongly dependent on pH, a higher pH resulting in a higher oxidation rate. Furthermore, when the pH exceeds 7.0, the oxidation rate constant increases significantly. Secondly, a column experiment was carried out under the conditions of the pH ranging from 6.8 to 7.5 and the natural oxygen supply. Ferrous iron oxidation and precipitation were found to reach equilibrium under these conditions. After 23 days, the column experiment was stopped when the clogging materials blocked the column outlet. The clogging materials were found to be a mixture of ferric hydroxide and its converted products, and these existed in amorphous form with a loose cluster microstructure according to the results of XRD and SEM.     

Field investigations and laboratory simulation of clogging in Lixi tailings dam of Jinduicheng,China

Clogging is one of the most important factors affecting the stability of the tailings dams. Firstly, this work investigates the clogging materials of Lixi tailings dam using ICP-AES, X-ray powder diffraction (XRD) and SEM analysis methods. The ICP-AES results indicate that Fe is the dominant element in the clogging materials. The iron contents of clogging samples collected from 2# radial-well pipe and the access hole of the starter dam are 54.35 and 40.24%, respectively. XRD spectra show that ferric hydroxide is the main initial component of the clogging materials. Other compounds such as akaganeite, hematite and goethite are products from ferric hydroxide transformation. Therefore, the clogging materials are a mixture of ferric hydroxide and its converted products. The clogging materials commonly exist in an amorphous form with a cluster microstructure when viewed under SEM. Secondly, this work uses a continuous flow column to simulate clogging in the laboratory, and the clogging materials are analyzed with XRD and SEM. The chemical analysis indicates that the iron content of the clogging materials from the experiment is 45.43%. XRD spectra show that hematite is the only compound detected. The clogging materials generated experimentally are also in amorphous cluster microstructure when viewed under SEM.     

Secondary copper enrichment in tailings at the Laver mine, northern Sweden

 Field and laboratory studies of the sulphide-bearing tailings at Laver, northern Sweden, show that the present release of metals from the tailings is low, especially with regard to Cu. A large part of the Cu released by sulphide oxidation is enriched in a distinct zone just below the oxidation front. The enrichment zone occurs almost all over the tailings area except in areas with a shallow groundwater table. The Cu enrichment is caused by formation of covellite and adsorption onto mineral surfaces. The transport of Zn, Co, Cd, Ni and S seems to be controlled mainly by adsorption. No secondary zone or secondary minerals containing these metals have been found. Just below the groundwater table, metals are released into solution when the enrichment zone reaches the groundwater due to the low pH. An increased release of metals, especially Cu, can be expected in the future, since the enrichment zone is moving towards the groundwater table. Received: 4 December 1997 · Accepted: 17 December 1998     

复杂地形尾矿坝的三维渗流分析

对于复杂地形的尾矿坝,由于二维模型不能充分反映复杂多变的渗流域,也不能考虑到三个方向渗流因素同时作用的影响,从而无法体现真正的渗流场。通过建立三维渗流数学模型,并考虑复杂断面概化和地形的简化,对实际工程进行了数值计算,其结果与试验结果吻合较好。结果表明,对复杂地形的尾矿坝渗流分析时必须采用三维模型,三维数值计算中对复杂地形进行适当的简化和概化对结果的影响较小,可以满足精度要求,因此大大减小了计算的复杂程度和难度。     

Uncertainty in dam safety risk analysis

The character and importance of uncertainty in dam safety risk analysis drives how risk assessments are used in practice. The current interpretation of uncertainty is that, in addition to the aleatory risk which arises from presumed uncertainty in the world, it comprises the epistemic aspects of irresolution in a model or forecast, specifically model and parameter uncertainty. This is true in part but it is not all there is to uncertainty in risk analysis. The physics of hazards and of failure may be poorly understood, which goes beyond uncertainty in its conventional sense. There may be alternative scenarios of future conditions, for example non-stationarity in the environment, which cannot easily be forecast. There may also be deep uncertainties of the type associated with climate change. These are situations in which analysts do not know or do not agree on the system characterisation relating actions to consequences or on the probability distributions for key parameters. All of these facets are part of the uncertainty in risk analysis with which we must deal.     

Combined analysis of electrical resistivity and geotechnical SPT blow counts for the safety assessment of fill dam

Electrical resistivity survey and the geotechnical SPT blow counts (N value) method were simultaneously analyzed to investigate the stability of a center-core type earth-fill dam against the seepage phenomenon. The coupling of these heterogeneous field methods provided a chance to understand the status of underground material by comparing the geophysical and geotechnical view. The analysis shows that the zones with low resistivity value generally have low N value, which means low stiffness. However, some zones with a high resistivity pattern are not accompanied by an increase of its N value, and are even showing a lower N value. These results imply that one should be careful to directly correlate resistivity value with the real status of the core material of a fill dam. And a highly resistive zone may be in poor status due to the effect of increase of resistivity value as a result of the piping condition. Additional laboratory tests show that there is a deficiency of fine soil particles believed as the clay at the troubled region, which means an increase in resistivity value. Therefore, multiple explorations should be planned to reduce the uncertainty in application of geophysical methods to dam safety evaluation in order to compensate the resistivity information of core material.     

尾矿堆积坝透镜体分布状态研究

尾矿堆积坝中尾砂透镜体具有复杂的分布状态，对坝体的稳定状况有极大影响。根据工程地质勘察所揭露出的透镜体长度信息，定义了一个分布系数米描述透镜体分布状态，并对德兴铜矿2^#尾矿坝、永平铜矿1^#尾矿坝、安徽某铜矿尾矿坝及银山铅锌矿尾矿坝主剖面进行了分析。结果表明，分布系数能较好地反映出尾矿堆积坝的沉积状况，即分布系数值越大，尾矿坝的沉积状况越好：分布系数与尾矿土的不均匀系数成正相关，与粉砂不均匀系数有定量的关系。这些结果对尾矿坝工程地质勘察资料的分析及尾砂沉积规律的认识可能会有重要意义。     

某尾矿坝毛细水带内的坝体材料物理力学特性研究

毛细水的存在将使尾矿坝坝体材料的物理力学特性发生较大变化,这种变化对尾矿坝的安全稳定势必产生影响,而国内外在此方面的研究工作却鲜有报道。为此,开展了某尾矿坝坝体材料现场取样、室内土工试验工作,并采用自制的毛细水带分层取样试验装置开展了长达6个月的毛细水上升测试工作,通过分层取样及土工试验,得到了毛细水带内尾矿砂的物理力学特性,进而系统地研究了毛细水带尾矿砂的含水率、重度、黏聚力、内摩擦角等物理力学指标随毛细水高度的变化特征。研究发现,毛细水带内尾矿砂的含水率和重度均随毛细高度而减小;黏聚力和内摩擦角的变化均随毛细高度和含水率呈先增大后减小的变化规律,其中内摩擦角的变化规律与以往相关研究所得结论并不完全相符,分析指出,这是由于毛细水和尾矿砂颗粒的表面特性所导致的;简要分析了抗剪强度随毛细高度的变化规律,发现其受毛细作用影响较大,呈先增大后减小的变化趋势。研究结果为坝体、边坡等工程的稳定性研究工作提供了一种新思路,为今后建立考虑毛细水作用下尾矿坝稳定性分析方法和理论奠定了基础。     

米箭沟尾矿坝加高方案渗流场数值分析

米箭沟尾矿坝为了进行加高设计而进行了尾矿库区的地质钻孔勘探。基于实际钻孔勘探成果的最佳反演分析各分区-尾矿砂、风化岩体和初期坝堆石体的模型渗透参数和加高设计方案,采用三维有限元数值计算方法,应用自主开发的3D-Seepage-Stress程序进行了该尾矿坝加高后渗流场数值分析,得出渗流场各要素分布图。可以看出,在此加高方案下,尾矿坝库区浸润线和溢出点都很高,不利于尾矿坝的稳定安全和运行管理。为此提出了在加高方案设计中加强排渗设施设计的初步方案与建议。     

龙凤山水库土石坝电阻率层析成像无损检测技术

层析成像是近年来得到蓬勃发展的一项无损检测新技术,具有信息量丰富、准确、直观的独特优势,因此,在土石坝无损检测中正发挥着越来越重要的作用。在阐述电阻率层析成像基本理论的基础上,对龙凤山水库土石坝进行一系列层析成像无损检测,查明了龙凤山水库土石坝的渗漏通道,同时也证实了利用这一方法进行土石坝无损检测的可靠性。现场试验表明,层析成像无损检测技术可以在土石坝的病害检测中推广应用。     

Changes to dam safety management in British Columbia triggered by failure of a small earth dam

The Testalinden earth dam in southern British Columbia failed in June 2010 and created a huge debris flow. Homes were destroyed and property was damaged. The failure of this small dam resulted in a comprehensive review of over 1000 dams in the province, evaluation of dam safety management practices, changes to the Water Act and improvements in how data on dams are collected, archived and communicated. The provincial dam inventory was re-evaluated to ensure that appropriate consequence classification, and therefore attention, is assigned to dams. Increased scrutiny was placed on dam owners to ensure they complied with dam safety policies and to ensure they submitted annual inspection reports and formal dam safety reviews in a timely manner. Dam owners and professionals engaged in dam safety activities have received new guidelines and better education and training.     

Recent horizontal stress directions in basement rocks of southern Sweden deduced from open microcracks

The strike direction of open intragranular microcracks in quartz and feldspar host grains was determined using optical transmission and reflection microscopy on eight oriented samples taken in two study areas in Precambrian basement rocks of southern and south-central Sweden.For an area of about 160 km² (SW of Västervik) and two sample locations (W of Uppsala), the vast majority of open microcracks displays a strong preferred NW–SE strike direction. According to the common assumptions that natural cracks in crystalline rocks are predominantly extensional (mode I), and that open cracks belong to the latest microcrack generation, these strike directions should reflect the (sub-) recent main horizontal stress direction (σH) of the recent tectonic stress field.This conclusion is supported by corresponding directions known from in situ stress measurements and focal plane solutions in the vicinity of the study areas. It is remarkable that even in samples taken close (i.e. a few hundred metres) to recently active large scale faults the orientation of microcracks does not deviate from this common direction. This may point to slip on already softened faults, very local stress reorientations (e.g. m-scale) or that local stress relief was accomplished by other processes at micro-scale, e.g. mechanical twinning in favourably oriented feldspar crystals, or slip on grain boundaries.     

某铀尾矿库区地下水238^U迁移模拟

将铀尾矿库核素迁移问题概括为均质多孔介质中稳定的二维水流条件下的三维溶质迁移问题,利用Visual Modflow软件（MT3D）采用全隐式差分法对某铀尾矿库放射性核素迁移进行了模拟研究,模拟值结果与浓度实测值较吻合,揭示了尾矿库放射性核素时空迁移规律。     

Formation and composition of cemented layers in low-sulphide mine tailings, Laver, northern Sweden

Cemented layers (hardpans) are common in carbonate or sulphide-rich mine tailings and where pyrrhotite is the predominating Fe-sulphide. Laver, northern Sweden, is an abandoned Cu-mine where the tailings have low pyrrhotite content, almost no pyrite and no carbonates. Two cemented layers at different locations in the Laver tailings impoundment were investigated, with the aim to determine their effects on metal mobility. The cementing agents were mainly jarosite and Fe-oxyhydroxides in the layer formed where the tailings have a barren surface, whereas only Fe-oxyhydroxides were identified below grass-covered tailings surface. Arsenic was enriched in both layers which also exhibit high concentrations of Mo, V, Hg and Pb compared to unoxidised tailings. Sequential extraction indicates that these metals and As were mainly retained with crystalline Fe-oxides, and therefore potentially will be remobilised if the oxic conditions become more reducing, for instance as a result of remediation of the tailings impoundment.An erratum to this article can be found at     

金堆城尾矿坝加高方案数值模拟及稳定性分析

金堆城尾矿坝为了进行加高设计而对尾矿库区进行了地质钻孔勘探。基于实际钻孔勘探成果,最佳反演分析了各分区-尾矿砂和初期坝堆石体模型的渗透系数、物理力学指标和加高方案下的浸润面分布。结合加高设计方案,采用基于有效应力法的EFES-3D计算程序对该尾矿坝加高后的应力应变场进行了数值模拟和坝坡稳定性分析,得出应力应变场分布图和边坡安全系数。可以看出,在上游法加高方案下,尾矿坝坝坡有涌起抬高现象,安全系数有所降低,不利于尾矿坝的稳定安全和运行管理。为此提出了在加高方案设计中加强排渗设施建议。     

尾矿坝非饱和带滞水曲线模型的建立及应用

本研究的目的是建立一种简单实用的上游式尾矿坝非饱和带滞水曲线的数学模型。研究方法采用拟合法。在揭示了硬岩尾矿砂的沉积距离与含水率、孔隙比等之间关系的基础上,建立了一种arctanx的函数,用来表征含水率与基质吸力的关系。将本模型应用于降雨入渗条件下饱和-非饱和渗流场分析,结果表明,数学模型与实验数据,具有明显的一致性。研究表明:该数学模型函数简单,适用于上游式尾矿坝。     

大坝安全诊断的混沌优化神经网络模型

为了提高大坝变形的预测精度,采用小波变换和分形理论对大坝位移观测数据的非线性动力学特性进行了分析,揭示了其具有低维混沌动力特性,这为大坝变形预测模型的建立提供了理论依据和先验知识。基于低维混沌动力特性,设计了能捕获大坝位移观测数据全局动力特性,兼具神经网络模型结构优化和动力机制时新的混沌优化神经网络大坝变形预测模型。在工程实例中,由多个度量指标组成量化评价体系,对模型预测性能进行综合评价,结果表明,所建模型比传统BP神经网络和ARMA模型具有更高的预测精度。     

Delineation of shallow resistivity structure in the city of Burdur,SW Turkey by vertical electrical sounding measurements

The city of Burdur, which is built on an alluvium aquifer, is located in one of the most seismically active zones in southwestern Turkey. The soil properties in the study site are characterized by unconsolidated and water-saturated sediments including silty, clayey and sandy units, and shallow groundwater level is the other characteristic of the site. Thus, the city is under soil liquefaction risk during a large earthquake. A resistivity survey including 189 vertical electrical sounding (VES) measurements was carried out in 2000 as part of a multi-disciplinary project aiming to investigate settlement properties in Burdur city and its vicinity. In the present study, the VES data acquired by using a Schlumberger array were re-processed with 1D and 2D inversion techniques to determine liquefaction potential in the study site. The results of some 1D interpretations were compared to the data from several wells drilled during the project. Also, the groundwater level map that was previously obtained by hydrological studies was extended toward north by using the resistivity data. 2D least-squares inversions were performed along nine VES profiles. This provided very useful information on vertical and horizontal extends of geologic units and water content in the subsurface. The study area is characterized by low resistivity distribution (<150 Ωm) originating from high fluid content in the subsurface. Lower resistivity (3–30 Ωm) is associated with the Quaternary and the Tertiary lacustrine sediments while relatively high resistivity (40–150 Ωm) is related to the Quaternary alluvial cone deposits. This study has also shown that the resistivity measurements are useful in the estimation of liquefaction risk in a site by providing information on the groundwater level and the fluid content in the subsurface. Based on this, we obtained a liquefaction hazard map for the study area. The liquefaction potential was classified by considering the resistivity distributions from 2D inversion of the VES profiles, the types of the sediments and the extended groundwater level map. According to this map, the study area was characterized by high liquefaction hazard risk.