渗流-蠕变耦合作用下全尾砂胶结充填体力学性能演化规律及损伤破坏机制

Reasonable determination of cemented crude tailings backfill mechanical indexes are closely related to safe production and economic benefits of mine, but the required mechanical indexes of crude tailings backfill are commonly determined by means of experience analogism in engineering practice, which lead to a high cost of backfilling and become one of the most difficult problems should be solved in crude tailings backfill mining technique. The long-term mechanical properties and damage mechanism of cemented crude tailings backfill are the bases for determining its reasonable mechanical indexes. This project intends to study the long-term mechanical properties, macro-failure characteristic—such as morphology and quantity of cracks on the surface and roughness of fracture surface, and meso-failure characteristics—such as morphology and pore structure of fracture surface, of cemented crude tailings backfill under seepage-creep coupling. The seepage-creep damage model for cemented crude tailings backfill could be established, and its long-term mechanical parameters can be obtained by isochronous stress-strain curve cluster method, steady rate intersection method combined with Mohr-Coulomb principle, then the evolution model of long-term mechanical parameters to instantaneous mechanical parameters could be established to reveal the evolution law of mechanical properties of cemented crude tailings backfill under seepage-creep coupling. The internal relationship between macroscopic failure and mesoscopic fracture will also be established to reveal seepage-creep damage mechanism of cemented crude tailings backfill. The study provides a basis for scientific determination of mechanical indexes of cemented crude tailings backfill in crude tailings backfill mining technique.

合理的全尾砂胶结充填体力学指标关系到矿山安全生产与经济效益，实践中常采用经验法来保守确定满足需要的全尾砂胶结充填体力学指标，导致充填成本居高不下，是全尾砂充填开采技术中亟需解决的难点之一。全尾砂胶结充填体的长期力学性能及损伤破坏机制是确定其合理力学指标的基础。本项目拟对渗流-蠕变耦合作用下全尾砂胶结充填体的长期力学性能，破坏后表面裂纹形态、数量和破裂面粗糙度等宏观破坏特征以及破裂面形貌、孔结构等细观破坏特征进行研究。建立全尾砂胶结充填体的渗流-蠕变损伤模型，利用等时应力-应变曲线簇法、稳态速率交点法并结合莫尔-库仑原理确定其长期力学性能参数，建立长期力学性能参数与瞬时力学性能参数之间的演化模型，揭示渗流-蠕变耦合作用下全尾砂胶结充填体的力学性能演化规律；建立宏观破坏与细观断裂之间的内在联系，揭示全尾砂胶结充填体渗流-蠕变损伤破坏机制；为全尾砂充填开采技术中充填体力学指标的科学确定提供依据。

合理的全尾砂胶结充填体力学指标关系到矿山安全生产与经济效益，其关键在于明确不同环境下全尾砂胶结充填体的力学特性和损伤破坏机制。本项目针对渗流-蠕变耦合作用下全尾砂胶结充填体力学性能演化规律及损伤破坏机制问题进行深入研究，探究渗流-蠕变耦合作用下全尾砂胶结充填体的蠕变特性与蠕变损伤模型、宏细观破坏特征及其内在联系、以及长期力学性能的演化规律。项目研究结果表明：渗流作用和围压对全尾砂胶结充填体的蠕变、宏细观破坏特征和长期力学性能有较大影响；全尾砂充填体的蠕变随渗透水压的增大而增大，围压越大，蠕变越明显；结合蠕变基本力学元件和损伤理论，建立的蠕变损伤模型能较好反映渗流作用对全尾砂胶结充填体蠕变的影响效应；随着渗透水压的增加，全尾砂胶结充填体的宏观破坏形式逐渐从张拉破坏向剪切破坏过渡，表面宏观裂纹逐渐增多，破裂面分形维数越大，破坏程度逐渐提高；渗透水压越大，全尾砂胶结充填体蠕变过程中内部萌生和发育的孔隙越多、孔隙结构越复杂、孔隙的分形维数越大，导致其结构越多孔疏松、损伤越严重，从而使得全尾砂胶结充填体的宏观变形越大，围压的增大可以降低渗透水压对全尾砂胶结充填体的损伤；全尾砂胶结充填体的长期抗压强度、长期抗剪强度、长期粘结力和长期内摩察角随渗透水压的增加而降低，且充填配比越低，渗透水压对全尾砂胶结充填体的长期力学性能的劣化影响越明显，较大围压下全尾砂胶结充填体的长期力学性能较好；渗透水压的增大导致全尾砂胶结充填体结构越多孔疏松，宏观变形积蓄的能量越大，内部结构缺陷扩展形成宏观破坏的需要消耗的能量越大，从而导致全尾砂胶结充填体破裂方式从低耗能的脆性破裂方式逐渐向高耗能的韧性破裂过渡。项目研究成果在一定程度上揭示了渗流-蠕变耦合作用下全尾砂胶结填体的力学性能演化规律和损伤破坏机制，可为全尾砂充填开采技术中充填体力学指标的科学确定提供一定的依据。