矿山排土场碎屑流灾变机制细-宏观研究

Mining waste dumps are essentially coarse aggregates consist of multi-scale granular, which are potential catastrophe sources, such as large-scale landslides, debris avalanche, run-out flow slides and debris flows. Debris avalanche is key, resulting from the inherent structural character of medium. Based on scale dumping flow shear model test(SDFS), characteristic blocks track records(CBTR) datas during the actual dumping process, and revealed outcrop, multiscale conceptional stratigraphic sequence model for mining waste dump is built, which implies inclined multilayer sequence structures and spatial particle-size distribution, and accords with the actual waste dump construction procedure such as dumping, flowing, segregation. The relation between the meso-fabric characteristics and the macroscopic mechanics behaviours of granular medium is established by multiscale characterization methods, based on large triaxial tests and in situ tilt shear tests, combining with discrete element numerical simulation (e.g., PFC). Micro-macro mechanism and deformation behaviours of waste dumps is revealed, consequentially characteristics extrapolation method of scale restructuring samples to full graded condition. Based on particle shear flow numerical simulation(PSLNS), combining with SDFS and CBTR, microscopic transforming mechanics for granular jamming to flowing are discussed, corresponding to the waste dump landslide & debris avalanche initiation macro-mechanics. Accordingly, the meso phase transition behavior, from quasi-solid to quasi-liquid, of granular under shear flow conditions are being interpreted, corresponding to the macroscopic debris avalanche mechanisms of waste dump. The research achievement will provide theoretical basis for safety assessment of waste dumps and disaster prevention and mitigation.

矿山排土场本质上是多尺度散体集合体。碎屑流破坏是潜在灾变（大规模滑坡、碎屑流、远程流滑及泥石流）问题的核心，反映散体介质固有性质及其结构性影响。基于缩尺倾倒流动模型试验，现场排土全过程特征块体跟踪记录，及剖面揭露，构架符合实际排土场工程倾倒-流动-分选过程，隐含倾斜分层结构特征及空间粒度分布特征的多尺度散体层序模型；采用大三轴和原位倾斜剪切试验，结合离散元（特别是颗粒流），根据散体多尺度表征方法，建立散体细观结构特征和宏观特性的联系，揭示排土场散体的细-宏观力学特性和变形机理，得到多尺度散体介质缩尺重组样在全级配条件下的外推方法。综合颗粒剪切流动数值模拟、缩尺倾倒流动模型试验和现场排土全过程特征块体跟踪记录，研究细观层面的颗粒阻塞与流动转化机制，及其对应的宏观层面的排土场干性碎屑流和滑坡启动机制；建立细观层面的流动过程中类固态与类液态力学行为的相变条件与宏观的排土场碎屑流灾变机制的联系。

矿山排土场本质上是多尺度散体集合体。碎屑流破坏是潜在灾变问题的核心，反映散体介质固有性质及其结构性影响。基于缩尺倾倒流动模型试验及剖面揭露，构建符合实际排土场工程的倾倒-流动-分选过程，建立隐含倾斜分层结构特征及空间粒度分布特征的多尺度散体层序模型。认识到分选机制关键在于内层整体推移和外层流动并存，进而形成反序结构。提出上部滞留带、中部静力堆积带、下部重力堆积带、外表散粒、内部摩阻层的三带二层结构模型；采用300多组大三轴和原位倾斜剪切试验，结合高压固结试验，根据散体多尺度表征方法，建立散体细观结构特征和宏观特性的联系，揭示散体细-宏观力学特性和变形机理，得到了散体缩尺重组样全级配条件下的外推方法。提出了适合排土场工程的邓肯和MC非线性分段强度准则，克服线性强度指标计算结果安全系数偏小、滑动面分布过浅的缺点，解析了唯象性安息角和静内摩擦角以及动摩擦角之间的内在联系。综合颗粒剪切流动数值模拟、缩尺倾倒流动模型试验，研究细观层面的颗粒阻塞与流动转化机制，及其对应的宏观层面的排土场干性碎屑流启动机制。识别了从滑坡启动到碎屑流通最终堆积的过程：高台阶土场超载作用→坡趾下部前缘侧向隆起→剪出滑坡→“离层空化”→二级滑坡→整体塑性流动。力学作用相当于超载挤压作用，致使排土场中下部发生较高量级的侧向（水平向为主）位移变形。细观层面，自由表面（临空面）的废石颗粒脱离既有邻近颗粒之间的咬合嵌固约束，在重力作用下沿坡面向下离析运动，进而诱发邻近颗粒相继移动。粒间离散过程具连锁性和放大作用，并导致既有骨架的松散化。宏观层面，散体堆积体在高应力作用下呈现应变软化和峰后强度突变-塑性流动特征，并导致剪应变增量区的高梯度集中。建立了细观层面的流动过程中类固态与类液态力学行为的相变条件与宏观的排土场碎屑流灾变机制的联系。远程流滑灾变过程是颗粒在快速流动下瞬时接触并通过碰撞传递动量，表现出类似液态材料的行为。类固态（滑坡）向类液态（远程流滑）的转变过程中，不同粒径（粉粒、细粒、粗粒、砾石到巨粒）颗粒间的相互作用会因细观上剪切速度和密集度的细微变化，引发不同的宏观表现。滑动距离受滑动路径、材料（滑动路径覆盖层及排土体）力学性质及其流动性、破坏规模等因素的控制。工后沉降机制在于废石颗粒细化-滑移-充填孔隙；空间上受地基坡度-堆积高度影响；散体性质（强度）表现为随废石堆积体固结度变化而导致时间效应。