大范围顶板岩体垮落冲击动载对采场底板破坏的影响研究

Influence of impact load induced by large-scale roof caving on the failure characteristics of mining floor

为研究大范围顶板岩体垮落产生的冲击载荷对采场底板的破坏作用及其对底板突水的影响,本文基于动力基础半空间理论,将底板岩层等效为半空间无限体,建立顶板岩体垮落冲击采场底板的理论分析模型,推导出最大冲击动载应力的计算公式;并利用FLAC3D模拟分析了顶板垮落产生的冲击动载在底板中的传递规律以及底板岩层的动力响应特征。研究结果表明:顶板岩体垮落撞击采场底板,会产生远大于垮落岩体静态自重的冲击动载应力作用在底板上;冲击动载荷以应力波的形式在底板中传播,与采动应力叠加产生动态应力集中现象,会导致采场底板发生二次破坏,造成底板破坏深度显著增大,有效隔水层厚度减小,从而增加底板突水的危险性。

In order to research the failure regularity of mining floor and the influence on floor water inrush under impact load caused by large-scale roof caving, the mining floor is simplified as semi-infinite half space, the theoretical calculation model for the impact load has been established based on the dynamic theory of elastic half-space foundation, and calculation formulas for the maximum impact load stress has been deduced in this paper. The propagation rules of stress wave in the rock stratum and the mechanical response of floor strata under the action of dynamic disturbance have been simulated and analyzed with the FLAC3 D software. The results have shown that the impact load caused by roof rock mass caving is often much greater than the weight of the collapsed rock mass. The impact dynamic load propagates in the coal floor superposed by mining-induced stress causes dynamical stress concentration. Consequently, the impact load gives rise to secondary damage of the floor rock masses, which leads to the increase of the maximum failure depth of mining floor. So, the risk of floor water inrush is greatly increased due to the decreasing of effective thickness of water-resisting layer.