A study of large-scale triaxial shear test of the mechanical properties of abandoned materials
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摘要: 露天矿剥离堆积的排弃物料力学性质是矿山排土场设计与稳定性控制之关键科学问题。文章以西南某露天矿剥离排弃物料为研究对象，采用室内相似级配模拟试验制作了不同物质组成、级配、相对密度条件下的试样，采用剪后筛分试验研究了各试样在不同应力状态下的颗粒破碎机理及破碎率变化关系，采用大型三轴剪切试验测试了各试样的应力-应变关系及抗剪强度参数。试验结果表明：排弃物颗粒剪切破碎力学机制复杂，颗粒破碎率与物料组分、级配、相对密度及围压条件密切相关，与抗剪强度参数相关性强。应力-应变曲线无明显峰值强度，具有应变硬化特征，分析认为其与围压、相对密度水平较低有关。试验数据拟合曲线均表明：ε1/（σ1-σ3）与ε1为线性关系，-ε3与ε1为抛物线关系，相关系数均大于0.9。据此拟合曲线，求解出排弃物料的切线泊松比μt，修正了邓肯-张模型。对相同试验条件下对比试样（QG-B-3）应力-应变关系，采用邓肯-张模型（修正）进行了预测，预测结果与试验测试数据基本一致，验证了邓肯-张模型（修正）能够描述排弃物料力学特征。研究排弃物料剪切破碎机理与应力-应变特征，对露天矿排土场边坡变形控制具有重要的理论意义。Abstract: The mechanical properties of materials discharged by stripping and stacking in open-pit mines are the key scientific problem in dump slope design and stability control. In engineering practice, the empirical method and the engineering geological analogy method are often used to estimate the mechanical parameters, but the effect of abandoned material properties and stress state on the mechanical properties is not fully considered, and the reliability of the stability calculation results of the dump slope is low. In this study, the abandoned materials of an open-pit mine in southwest China is taken as the research object, the experimental samples with different material compositions, gradation and relative densities were made by the similar gradation simulation experiment. The particle crushing mechanism and mechanical properties of each sample under different stress conditions were examined by the post shear screening experiment and large-scale triaxial shear experiment. The experimental results show that the particle breakage rate is closely related to the material compositions, gradation, relative densities and confining pressure conditions, and is strongly related to the shear strength parameters. Under the condition of low confining pressure and low relative density, the stress-strain curve has no obvious peak strength and is of the characteristic of strain hardening. The fitting curves of experimental data show that ε1/(σ1-σ3) and ε1 has a linear relation, -ε3 and ε1 has a parabola relation. Based on that fitting curve, the tangent line Poisson’s ratio μt of the abandon material is obtained, and the Duncan-Chang model is modified. The experimental test data of the contrast sample (QG-B-3) under the same experimental conditions prove that the Duncan-Chang model (modified) can describe the stress-strain characteristics of the abandon material. The shear crushing mechanism and stress-strain characteristics of the abandon materials are of important theoretical significance for dump slope deformation control in the open pit mines.
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