结构瞬变激励下采场煤岩静态力学响应的阶变机理

Step change mechanism of static mechanical response of coal-rock in stope under structural transient excitation

  • 摘要: 揭示采场煤岩力学响应的发生机理是煤岩灾害防治的理论基础。采用现场实测、模拟试验和理论分析相结合的研究方法,通过构建结构瞬变前、后2个稳态时的静力学模型,系统研究了采场煤岩静态力学响应阶变的发生机理。结果显示:采场煤岩的力学响应与覆岩空间结构的瞬变特征密切相关,初次来压时,覆岩空间结构的瞬变具有对称性,造成其诱发的力学响应亦具有对称性;周期来压时,结构瞬变区域主要集中于工作面侧,造成其诱发的力学响应亦集中于工作面侧煤岩中;结构瞬变诱发的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,导致不同区域煤岩的力学响应存在显著差异。其中,下位坚硬岩层的瞬时破断会在上位坚硬岩层的下表面形成瞬时卸载,使其瞬时下沉。与此同时,下位坚硬岩层破裂面内力的瞬时卸载,以及结构瞬变区域支撑载荷向采空区外侧转移形成的瞬时加载,会使下位坚硬岩层临近采空区侧的部分区域瞬时回弹,而深部围岩中的部分区域瞬时下沉;受此影响,下位坚硬岩层上表面的承载量瞬时增大,支承压力峰值骤增、峰值位置向采空区侧跃迁。同时,受下位坚硬岩层的破断卸荷和下沉−回弹影响,煤体上的承载量瞬时减小,支承压力峰值骤减、峰值位置向煤体深部跃迁。随着结构瞬变区域转移载荷量的增大,下位坚硬岩层的回弹量减少,而煤体的承载量增大;随着转移载荷作用范围的增大,下位坚硬岩层的回弹量增大,煤岩受载的阶变量减小而阶变范围增大。

     

    Abstract: Revealing the occurrence mechanism of coal-rock mechanics response in the stope is theoretical basis for the prevention and control of coal-rock disasters. By adopting a combination of field measurements, simulation experiments, and theoretical analysis, the occurrence mechanism of step changes in the static mechanical response of coal-rock in the stope was systematically studied through the construction of static mechanical models at two steady states before and after structural transient. The results show that the mechanical response of coal-rock in the stope is closely related to the transient characteristics of overburden spatial structure. During the first weighting, the structural transient of overlying strata exhibits symmetry, leading to a symmetrical mechanical response. During periodic weighting, the structural transient region is mainly concentrated on working face side, resulting in a mechanical response that is also concentrated in coal-rock masses on the working face side. The transient change in the load transfer path of the overlying strata, induced by structural transient change, causes different instantaneous loading and unloading conditions for coal-rock in various areas of the stope. It leads to significant differences in the mechanical responses of coal-rock in these areas. Among them, the instantaneous fracture of lower hard rock layer forms instantaneous unloading on the lower surface of upper hard rock layer, causing it to sink instantly. Meanwhile, the instantaneous unloading of internal forces along fracture surface in lower hard rock layer, coupled with the transient loading induced by transferring support load from structural transient region towards goaf, causes the instantaneous rebound in some areas near goaf side of lower hard rock layer. The instantaneous subsidence of some areas in the deep surrounding rock. Affected by this, the bearing capacity of the upper surface on the lower hard rock layer increases instantaneously. It leads the peak support pressure suddenly increases, and its position transitions towards the goaf side. Meanwhile, affected by the fracture unloading and subsidence-rebound of the lower hard rock strata, the bearing capacity on the coal body decreases instantaneously. The peak value of abutment pressure on coal body decreases sharply, and its position transitions to the depth of coal body. With the increase of transfer load in structural transient region, the rebound amount of lower hard rock decreases, while the bearing capacity of the coal body increases. With the increase of action range of transfer load, the rebound amount of lower hard rock increases. The step change of coal-rock load decreases, while the range of step change increases.

     

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