采动应力旋转的内涵、原理、表征与工程应用

Definition, principle, characterization and application of mining-induced stress rotation

  • 摘要: 采动应力是矿井围岩变形破坏的直接诱因,也是支护设计的前提基础,决定了围岩控制效果。由于煤炭开采强度和深度增加,采动应力分布趋于复杂,围岩失稳和动力灾变频率升高,控制难度增大。为保障煤炭资源安全高效开采,综合运用现场实测、理论分析、室内试验、数值计算等手段,发现了采动应力旋转现象,阐述了应力旋转的科学内涵、力学原理、表征方法及其在采矿工程中的应用实例。首先采用空心包体应变计实测了地应力张量和采动应力增量,提出了绝对采动应力计算方法;揭示了采动应力张量矩阵与主应力、主方向的关系,定义了采动应力旋转的科学内涵;基于应力张量矩阵变换特征给出了3种采动应力状态变化模式:主应力变化,主方向不变(I);主应力不变,主方向变化(II);主应力和主方向同时变化(III)。实测结果表明采动应力张量属于变化模式III,验证了应力旋转现象的存在性。阐明了岩层运动、采动卸荷导致采动应力渐进旋转及应力集中、释放导致大小主方向突变的力学原理。建立了采动应力旋转的极射赤平投影分析模型,得到了3类采动应力旋转轨迹,将三维空间旋转问题退化为二维平面问题,实现了旋转幅度和方位的定量分析;探讨了采动应力旋转与围岩稳定性的关系,以采动应力旋转轨迹为基础,提出了围岩稳定性的应力方向敏感区识别方法,实现了围岩破坏裂隙萌生位置和扩展方向的准确预测;阐述了采动应力旋转在“采掘工作面设计、顶板稳定性分析与支架选型、深部工作面断层活化治理、超长工作面围岩分区控制、拱形综放工作面强矿压控制”5类场景中的应用案例,形成了以采动应力旋转轨迹调控为核心的围岩控制技术,从开采源头提升围岩自承载能力,为矿井围岩控制提供新思路。

     

    Abstract: Mining-induced stress leads to the deformation and failure of surrounding rock. It serves as the premise for support design, determining ground control effectiveness. With the growth in mining intensity and depth, the distribution of mining-induced stress becomes increasingly complex. The frequency of rock instability and dynamic disaster rises, and rock control difficulty increases. To ensure the safe and efficient mining of coal resources, the phenomenon of mining-induced stress rotation was identified by applying field measurement, theoretical analysis, lab experiment and numerical simulation. The scientific definition, mechanical principle, characterization method and its application prospect in mining engineering were systematically clarified. Initially, the ground stress tensor and mining-induced stress increment were obtained by the CSIRO cell, and the calculation method for absolute mining-induced stress was proposed. It revealed the relationship between mining-induced stress tensor matrix and the principal stresses as well as principal directions. The definition of mining-induced stress rotation was then put forward. Based on transformation characteristics of the stress tensor matrix, three mining-induced stress changing modes were determined: principal stress changed while principal direction unchanged (I), principal stress unchanged while principal direction changed (II), and both principal stress and principal direction are changed (III). In-situ data showed that mining-induced stress changing mode belonged to type III, which verified the existence of stress rotation. Subsequently, mechanical principle of stress rotation was investigated, which was attributed to strata movement, stress release and stress concentration. The polar stereographic model was established for mining-induced stress rotation. Three types of rotation trajectory were identified for mining-induced stress. Three-dimensional space rotation problem was simplified into two-dimensional plane problem, enabling quantitative analysis of the rotation amplitude and orientation. Additionally, the relationship between mining-induced stress rotation and surrounding rock stability was explored. Based on the mining-induced stress rotation trajectory, a method for identifying the sensitive zone of rock stability to stress orientation was moreover proposed. The accurate prediction of initiation position and propagation path of failure fractures in the surrounding rock was achieved. Furthermore, five application scenarios of mining-induced stress rotation in underground mining were presented, including the optimization of mining and tunnelling faces, stability analysis of roof structure and support selection, activation prohibition of the fault in deep mining, zonal control of surrounding rock in the panel with large face length, and strong mining pressure control in LTCC with arch-shaped panel. At last, a new surrounding rock control technology was formulated by optimizing stress rotation trajectory. The new method aims to enhance self-bearing capacity of surrounding rock from the source of mining, which provides new idea for surrounding rock control in underground mining.

     

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