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etude experimentale de la resistance en traction de residus miniers non satures a l'aide d'essais de flexion.

机译：弯曲试验的非饱和矿山尾矿抗拉强度试验研究。

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摘要

The responsible disposal of mining wastes is a challenge that needs to be addressed. Mining operations produce a variety of waste materials such as waste rocks and tailings. Tailings, which contain a high percentage of fine particles, are generally stored in an initially saturated state, in tailing impoundments surrounded by dikes. Over time, such tailings tend to consolidate, and may become unsaturated due to drainage and evaporation, which makes their behavior more complex. It is important to understand the behavior of unsaturated tailings in order to predict their response in the field.;Unsaturated tailings (as well as soils) as submitted to a negative water pressure (suction). This negative pressure creates capillary forces that contribute to the cohesion between particles. This apparent cohesion is not an inherent (intrinsic) property of the material as it varies with the amount of pore water and the related degree of saturation. The apparent cohesion is correlated to the tensile strength and it has a significant impact on the mechanical behavior of unsaturated materials such as mine tailings.;This project focused on the evaluation of the tensile strength of unsaturated mine tailings. Several studies on this subject have been carried out on clayey soils and cemented materials, but granular (cohesionless) materials such as tailings from hard rock mines have not received much attention. Thus, this research aimed at developing a better understanding of the tensile behavior and associated properties (i.e. apparent cohesion and modulus of elasticity) of unsaturated tailings.;The methodology consisted of experimental tests and numerical analyses. The laboratory tests were performed on three types of tailings, with fairly similar properties, obtained from different mine sites. The laboratory testing program included the development of an experimental method, based on bending tests, to assess the tensile strength as a function of the degree of saturation of the tailings. For this purpose, prismatic moulds used to perform shrinkage tests were used to prepare the specimens. The homogeneity of these specimens (in terms of water content) was examined to validate the preparation procedure. The results demonstrated that the water content is relatively constant in the prismatic specimens.;The force and deformation measured up to failure during 67 bending tests are presented in the thesis. The measured data were analyzed using the elastic theory to determine the tensile strength of the samples. These provide relationships between tensile strength and degree of saturation. The experimental study also included the evaluation of effect of the void ratio (initial and final) on the tensile strength. The experimental values of the tensile strength were also compared with results obtained from predictive models.;Young's modulus was also determined using the strength and measured vertical deflection during the bending tests on tailings. The tensile strength values were also used to assess the apparent cohesion as a function of the degree of saturation using the effective angle of internal friction (obtained from another study). The relationship between suction and tensile strength (and apparent cohesion) was also investigated.;In addition, the finite element code SIGMA/W 2007 (Geo-Slope Inc) was used to simulate the results from bending tests conducted on tailings at different water contents. The basic geotechnical properties of the tailings and the measured force up to the specimens' failure were used to reproduce the experimental observations. The numerical simulations were carried out using the linear elastic and elastic-plastic constitutive laws. Calculations resulted in vertical deflection, tensile strain and tensile strength values that are quite close (but usually smaller) to the experimental results. The effect of Young's modulus and apparent cohesion on the specimen behavior was also investigated using the elastic-plastic (EP) model. The results indicate that these two parameters can have a significant influence on the deflection (and deformation) and stress state within the tailings specimens.;The influence of geometrical factors (i.e. thickness h and length L), Poisson's ratio and loading rate was also investigated numerically. The results show that increasing the specimen thickness tends to decrease the time for failure, which is related to the apparition of yield zones in the model. Increasing the specimen length L increases the vertical deflection and the failure time. These simulations indicate that the Poisson's ratio only has a small effect on the response of the material during such bending tests.;This research fulfilled the initial objectives and addressed other important issues related to the strength of unsaturated tailings. The results presented here should be useful for future work on their geotechnical behavior.
机译：负责任地处置采矿废料是需要解决的挑战。采矿作业产生各种废料，例如废石和尾矿。尾矿中含有大量的细小颗粒，通常以初始饱和状态储存在堤防包围的尾矿库中。随着时间的流逝，这些尾矿趋向于固结，并可能由于排水和蒸发而变得不饱和，这使其行为更加复杂。重要的是要了解不饱和尾矿的行为，以便预测它们在野外的响应。;不饱和尾矿（以及土壤）在负水压（吸力）作用下。此负压会产生毛细作用力，从而有助于颗粒之间的凝聚。这种表观凝聚力不是材料的固有（固有）特性，因为它随孔隙水量和相关的饱和度而变化。表观内聚力与抗拉强度有关，它对不饱和材料如矿山尾矿的机械性能有重大影响。在黏性土壤和胶结材料上已经进行了有关该主题的几项研究，但是诸如硬岩矿的尾矿之类的颗粒状（无粘性）材料并未引起太多关注。因此，本研究旨在更好地理解不饱和尾矿的拉伸行为及其相关性能（即表观内聚力和弹性模量）.;该方法包括实验测试和数值分析。实验室测试是对从不同矿场获得的三种类型的，具有相当相似性能的尾矿进行的。实验室测试程序包括开发基于弯曲测试的实验方法，以评估作为尾矿饱和度的函数的拉伸强度。为此，使用用于执行收缩测试的棱柱形模具来制备样品。检查这些样品的均质性（以水含量计）以验证制备程序。结果表明，棱柱形试样含水量相对恒定。本文提出了在67次弯曲试验中直至破坏的力和变形。使用弹性理论分析测量数据以确定样品的拉伸强度。这些提供了抗拉强度和饱和度之间的关系。实验研究还包括评估空隙率（初始和最终）对拉伸强度的影响。还将抗拉强度的实验值与从预测模型获得的结果进行了比较。杨氏模量还使用强度和在尾矿弯曲试验期间测得的垂直挠度确定。抗拉强度值还用于评估表观内聚力，该表观内聚力是使用有效内摩擦角（根据另一项研究得出）作为饱和度的函数。还研究了吸力与拉伸强度（和表观内聚力）之间的关系。此外，使用有限元代码SIGMA / W 2007（Geo-Slope Inc）模拟了在不同含水量下对尾矿进行弯曲测试的结果。尾矿的基本岩土特性和测得的直至试样破坏的力被用来再现实验结果。使用线性弹性和弹塑性本构定律进行了数值模拟。计算得出的垂直挠度，拉伸应变和拉伸强度值与实验结果非常接近（但通常较小）。还使用弹塑性（EP）模型研究了杨氏模量和表观内聚力对样品行为的影响。结果表明，这两个参数对尾矿样品的挠度（变形）和应力状态有显着影响。；还研究了几何因素（即厚度h和长度L），泊松比和加载速率的影响数值上。结果表明，增加样品厚度倾向于减少失效时间，这与模型中屈服区的出现有关。样品长度L的增加会增加垂直挠度和破坏时间。这些模拟表明泊松比在这种弯曲试验中对材料的响应影响很小。这项研究满足了最初的目标并解决了与不饱和尾矿强度有关的其他重要问题。这里介绍的结果对于他们的岩土行为的未来工作应该是有用的。

著录项

  • 作者

    Narvaez, Yuri Bibiana.;

  • 作者单位

    Ecole Polytechnique, Montreal (Canada).;

  • 授予单位 Ecole Polytechnique, Montreal (Canada).;
  • 学科 Engineering Mining.;Engineering Civil.
  • 学位 M.Sc.A.
  • 年度 2013
  • 页码 328 p.
  • 总页数 328
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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