多重采动作用下顶板岩层动态破裂及能量演化机制研究

The superimposed influence of multi-seam mining has become a problem of deep mining of coal resources in China. This project takes the inter-seam mining roof strata in multi-seam mining as the research object, and studies the dynamic fracture and energy evolution mechanism of the multi-seam mining roof strata in view of the problems such as the inter-seam stress (roof pressure) transfer and crack (water conduction crack) expansion. Research contents: .1）The simulates the influence of multiple mining by cyclic loading and unloading, analyzes mechanical behavior characteristics of coal and rock mass about the peak stress surface and post-peak under multiple loading and unloading, establishes the dynamic evolution model of mining-induced fracture of coal and rock mass, and reveals the micro-damage and failure mechanism of coal and rock mass under multiple mining conditions..2) Taking mining roof strata as a typical stress unit, an iterative correlation model of superimposed stress transfer and deformation of mining strata is established to study the stress transfer mechanism of multiple mining strata and the dynamic evolution law of fractures under different coal strata structure conditions, so as to reveal the correlation mechanism between stress and fractures..3) Studying multiple mining coal rock mass deformation and destruction instability and energy accumulation and release characteristics, analysis of energy accumulation and release characteristics and evolution of space and time, how to cause the mine disaster. Reveal the energy transfer mechanism of rupture instability multiple mining roof strata, gives its rupture instability energy criterion, provides the judging basis for the mining engineering disaster prevention and control.

多煤层开采叠加影响已成为我国煤炭资源向深部开采所面临的问题。本项目以多煤层开采中煤层间采动顶板岩层为研究对象，针对层间应力（顶板来压）传递和裂隙（导水裂隙）扩展等问题，开展多重采动顶板岩层的动态破裂及能量演化机制研究。研究内容：1）以循环加卸载模拟多重采动影响，通过实验分析多重加卸载煤岩体的峰值应力曲面和峰后力学行为特征，建立煤岩体采动裂隙动态演化模型，揭示多重采动条件下煤岩体的微细观损伤破坏机理。2）以采动顶板岩层为典型应力单元，建立采动岩层叠加应力传递与形变迭代关联模型，研究不同煤岩层结构条件下多重采动岩层的应力传递机理和裂隙的动态演化规律，揭示应力与裂隙的关联机制。3）研究多重采动煤岩体的变形、破坏失稳及能量积聚与释放特征，分析引发矿井灾害的能量积聚与释放的时空特征、演化规律，揭示多重采动顶板岩层破断失稳的能量转移机理，给出其破断失稳的能量判据，为采矿工程灾害防控及预测提供判别依据。

本项目以多煤层开采中采动顶板岩层为研究对象，开展三点弯曲载荷试验、多重循环加卸载力学行为试验、物理相似模拟实验、数值模拟等工作，研究多重采动作用下顶板岩层动态破裂及能量演化规律。通过三点弯曲载荷试验，对比不同强度岩石及其组合体的裂隙扩展行为，揭示了多重采动条件下复合顶板岩层的穿层破坏规律，得出：顶板岩层在二次采动作用下产生微裂隙，微裂隙的积聚导致顶板发生宏观损伤破坏，沿一次采动裂隙扩展，并在顶板岩层交界面发生水平迁移后继续向上扩展。通过多重采动循环加卸载力学行为试验，分析单一煤岩体和煤岩组合体的力学行为和能量变化，研究了多重采动煤岩体的变形、破坏失稳及能量积聚与释放特征，结果表明：煤岩组合体的峰值强度与峰值应变主要受薄弱载体控制；顶板强度越高，同等应力条件下产生的弹性能和耗散能越小，但其破断时产生的弹性能和耗散能越大。通过物理相似模拟实验，以采动顶板岩层为典型单元，对比2m、5m、26m煤层间距对采动顶板岩层的影响，总结了多重采动条件下岩层的应力传递机理和裂隙的动态演化规律，结果表明：近距离煤层下行开采时，下位煤层顶板受多重采动影响破碎严重，无剧烈来压，工作面超前支承应力影响范围和采空区滞后影响范围较单一煤层开采增大；二次采动下裂隙主要表现为一次采动裂隙的再次张开和连通，同时向完整顶板继续扩展，产生新的裂隙，裂隙网络更为丰富。通过FLAC3D数值模拟软件，研究了多重采动下巷道围岩变形及巷道应力分布规律，结果表明：受多重采动影响，下位煤层巷道顶板岩层应力呈现出明显的不对称性；在保证一定支护强度的情况下，内外错相结合巷道布置方式是一种更为科学合理的布置方式。.通过该项目的研究，其结果可为多重采动围岩控制、煤层群开采巷道布置等提供一定的理论依据，对我国煤层群开采矿压显现规律的研究起到重要推动作用。