摘要: 使用包含废石的粗骨料进行矿山充填开采,不仅保证了充填体的强度要求,还降低了胶凝材料投入和固体废弃物处理成本。然而,此类材料容易发生骨料离析,进而导致充填体的不均匀变形和破坏。本文采用基于机器学习的图像分割方法(通过WEKA平台实现) 来表征试块劈裂面上的骨料分布信息。结果表明,骨料离析与质量分数和胶骨比的变化呈非线性关系,质量分数从81wt%上升到82wt%,胶骨比从10.00wt%上升到12.50wt%,分别代表了流体动力和骨料摩擦两种效应的激增及主导地位的转变。同时,本文利用附加应变计及数字图像相关技术 (DIC) 的单轴压缩测试分析了骨料离析影响下的充填体力学性能及破坏机理。结果显示,单轴压缩强度在数值上与离析程度无显著关联,但离析程度在一定程度上影响了弹性模量的发展趋势,骨料离析指数 (使用AAR SD定义) 小于1.63%的试块表现出较高的弹性模量。轴向方向上,试块的顶部区域更易首先形成宏观断裂面,而底部区域的可压缩性大于顶部区域,骨料离析的加剧扩大了不同区域变形和破坏特征的差异。对于均匀性不同的试样,在稳定变形阶段观察到515.00~1693.70 με的局部变形差异,骨料的极端不均匀分布导致试样裂纹快速贯通,继而形成宏观拉伸破坏,最终引发结构的过早失效。

Abstract: Utilizing coarse aggregates containing mining waste rock for backfilling addresses the strength requirements and reduces the expenses associated with binder and solid waste treatment. However, this type of material is prone to aggregate segregation, which can lead to uneven deformation and damage to the backfill. We employed an image-segmentation method that incorporated machine learning to analyze the distribution information of the aggregates on the splitting surface of the test blocks. The results revealed a nonlinear relationship between aggregate segregation and variations in solid concentration (SC) and cement/aggregate ratio (C/A). The SC of 81wt%–82wt% and C/A of 10.00wt%–12.50wt% reflect surges in fluid dynamics, friction effects, and shifts in their dominance. A uniaxial compression experiment, supplemented with additional strain gauges and digital image correlation technology, enabled us to analyze the mechanical properties and failure mechanism under the influence of aggregate segregation. It was found that the uniaxial compressive strength, ranging from 1.75 MPa to 12.65 MPa, is linearly related to both the SC and C/A, and exhibits no significant relationship with the degree of segregation in numerical terms. However, the degree of segregation affects the development trend of the elastic modulus to a certain extent, and a standard deviation of the aggregate area ratio of less than 1.63 clearly indicates a higher elastic modulus. In the pouring direction, the top area of the test block tended to form a macroscopic fracture surface earlier. By contrast, the compressibility of the bottom area was greater than that of the top area. The intensification of aggregate segregation widened the differences in the deformation and failure characteristics between the different areas. For samples with different uniformities, significant differences in local deformation ranging from 515.00 με to 1693.70 με were observed during the stable deformation stage. The extreme unevenness of the aggregate leads to rapid crack penetration in the sample, causing macroscopic tensile failure and resulting in premature structural failure.