基于结构动力学理论的矿震机理分析

Analysis of mining earthquakes mechanism based on structural dynamics theory

  • 摘要: 矿震是地下煤层开采中较常见的动力学现象,揭示矿震的力学原理是其灾害评价、预测及防治的前提和基础,采用理论分析方法,探讨了矿震的力学原理与主控因子,研究了矿震中覆岩的下沉−振动响应特征,及其作用下覆岩应变能、重力势能和动能的演变机理。结果显示:在结构动力学视角下,矿震是一类典型的自由振动,由坚硬岩层破断等采场煤岩结构子系统的瞬时失稳触发,由采场煤岩结构瞬变后的初始状态驱动,不需要外部能量的输入,耗散采场煤岩自身的势能(重力势能+应变能),受控于采场煤岩结构的力学性能与力学环境及其对应的瞬变特征。对于结构瞬变区域上方的覆岩,受坚硬岩层破断影响,覆岩载荷转递路径发生改变,采空区上方关键层上、下表面的承载量瞬时减小,采空区外侧关键层上表面的承载量瞬时增大。受此影响,关键层及其上覆岩层下沉−振动,其任意时刻的速度、位移和弯曲应变能线密度等响应特征均呈现出波动特性,且都以震源为中心迅速衰减。并且,在任意振动周期内,除了有能量的耗散外,亦存在不同能量间的相互转换;在第1个1/4周期内,重力势能向动能和应变能转换;在第2个1/4周期内,重力势能和动能向应变能转换;在第3个1/4周期内,应变能向重力势能和动能转换;在第4个1/4周期内,动能和应变能向重力势能转换。基于上述的理念,可以更直观地理解矿震中采场空间不同区域煤岩力学响应的发生机理及其内在关联等,为煤岩动力灾害的防控提供了新思路和新视角。

     

    Abstract: Mine earthquake is a common dynamic phenomenon in underground coal seam mining, and revealing its mechanical mechanism is the premise and foundation for disaster evaluation, prediction, and prevention. In this paper, the theoretical analysis method is used to investigate the mechanical principles and main control factors of the mine earthquake, and to study the sinking-vibration response characteristics of the overlying rock in the mine earthquake, and the evolution mechanism of the strain energy, gravitational potential energy and kinetic energy of the overlying rock under the action. The results show that mine earthquake is a typical type of free vibration from the perspective of structural dynamics. The mine earthquake is induced by the instantaneous instability of the coal-rock structure subsystem such as the fracture of the hard rock layer. After the transient, it is driven by the initial state of the coal-rock structure of the stope, and does not require the input of external energy. Mine earthquake dissipates the potential energy (gravitational potential energy + strain energy) of coal and rock in the stope, which is controlled by the mechanical properties and mechanical environment of coal and rock structure in the stope and its corresponding transient characteristics. For the overlying strata above the structural transient area, under the influence of the hard rock layer breaking, the load transfer path of the overlying strata has changed, the bearing capacity of the upper and lower surfaces of the key stratum above the goaf decreases instantaneously, and the bearing capacity of the upper surface of the key stratum outside the goaf increases instantaneously. Affected by this, the key stratum and its overlying strata sink and vibrate, and the response characteristics such as velocity, displacement and bending strain energy linear density at any time show fluctuation characteristics, and decay rapidly with the focus of the mine earthquake as the center. Moreover, in any vibration period, there is energy dissipation and mutual conversion between different energies. In the first 1/4 period, the gravitational potential energy is converted to kinetic energy and strain energy. In the second 1/4 period, the gravitational potential energy and kinetic energy are converted to strain energy. In the third 1/4 period, the strain energy is converted to gravitational potential energy and kinetic energy. In the fourth 1/4 period, kinetic energy and strain energy are converted to gravitational potential energy. Based on the concept of this paper, the occurrence mechanism and internal correlation of coal-rock mechanical response in different areas of stope space during mine earthquake can be understood more intuitively, which provides new ideas and new perspectives for the prevention and control of coal-rock dynamic disasters.

     

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