结构瞬变激励下覆岩应变能场和重力势能场的演变机理

Evolution mechanism of strain energy field and gravitational potential energy field of overlying rock under transient excitation of structure

  • 摘要: 揭示覆岩能量场的聚集与释放机理,是煤岩动力灾害防治的理论基础。采用模拟试验、数值计算和理论分析相结合的方法,通过构建坚硬岩层破断前、后2个稳态时的力学模型,对比分析了结构瞬变前、后采场煤岩受载的阶变特征,研究了结构瞬变激励下覆岩应变能和重力势能聚集与释放的演变机理。结果表明:受自重应力场和采动卸荷效应影响,采动影响范围内的各岩层相互作用、相互制约,存在紧密且复杂的力学联系。坚硬岩层破断诱发的结构瞬变,打破了岩层间原有旧秩序的平衡,导致岩层间的力学联系发生瞬变,覆岩载荷传递路径亦发生瞬变,覆岩的应变能场和重力势能场随之改变。并且,覆岩载荷传递路径的瞬变,会对采场空间不同区域的煤岩形成不同的瞬时加、卸载,造成不同区域覆岩能量的演变特征存在差异。这其中,下位坚硬岩层破断后,破裂面内力的瞬时卸载和覆岩载荷传递路径瞬变形成的瞬时加载,使其邻近采空区的部分区域瞬时向上回弹、释放应变能,回弹区以里的部分区域瞬时下沉、释放重力势能。与此同时,结构瞬变区域支撑载荷的瞬时卸载,使上位坚硬岩层瞬时下沉、变形量骤增,重力势能释放而应变能聚集。本质上,结构瞬变激励下采场煤岩的动力学响应过程,是采场煤岩原有时空结构被打破后向新时空结构演化的动力学过程,存在应变能、重力势能和动能的相互转换,并伴随有应变能和重力势能的聚集与释放。且整体而言,覆岩应变能的释放区域较小,主要集中在瞬时卸载区,其余区域瞬时增大;而重力势能的释放范围较大,仅在下位坚硬岩层的回弹区域略有增大。

     

    Abstract: Revealing the aggregation and release mechanism of overlaying rock energy field is the theoretical basis for the prevention and cure of coal-rock dynamic disasters. By means of simulation experiment, numerical calculation and theoretical analysis, the mechanical models of two steady states before and after hard rock breaking were established. The step change characteristics of coal and rock under load before and after structural transient were compared and analyzed. The evolution mechanism of strain energy and gravitational potential energy accumulation and release of overlying rock under structural transient excitation was studied. The results show that it is affected by self-weight stress field and mining unloading effect, the rock strata within the mining influence range interact and restrict each other, and there is a close and complex mechanical connection. The structural transient induced by hard rock breaking, it breaks the balance of the original old order between the rock strata. It leads to the transient change of the mechanical relation between the strata and the load transfer path of the overlying strata. The strain energy field and the gravitational potential energy field of the overlying strata change accordingly. In addition, the transient change of overburden load transfer path will cause different instantaneous loading and unloading of coal and rock in different areas of stope space, resulting in differences in the energy evolution characteristics of overlying strata in different regions. Among them, after the fracture of the lower hard rock stratum, the instantaneous unloading of the internal force of the fracture surface and the instantaneous loading formed by the transient transition of the load transfer path of the overlying rock make some areas near the goaf instantaneously rebound upward and release strain energy, the instantaneous subsidence and release of gravitational potential energy in some areas within the rebound zone. At the same time, the instantaneous unloading of the support load in the transient region of the structure makes the upper hard rock layer sink instantaneously and the deformation increase sharply, and the gravitational potential energy is released and the strain energy is accumulated. In essence, the dynamic mechanical response process of coal rock in mining field under transient excitation of structural is a dynamic process of the evolution of the original space-time structure of coal rock in mining field to the new space-time structure after the original space-time structure of coal rock in mining field is broken. There is a mutual conversion of strain energy, gravitational potential energy and kinetic energy, accompanied by the aggregation and release of strain energy and gravitational potential energy. On the whole, the release area of overlaying rock strain energy is small, mainly concentrated in the instantaneous unloading area, and the rest areas increase instantaneously. The release range of gravitational potential energy is large, and only the rebound area of the lower hard rock layer increases slightly.

     

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