爆破载荷作用下煤厚变异区损伤破坏特征实验研究

Tests for damage and failure characteristics of coal thickness variation area under blasting load

针对地质构造区域爆破施工容易诱发煤与瓦斯突出的现实情况,建立煤岩组合弹性力学模型、根据爆炸应力波在煤岩介质中的传播与作用规律,分析了煤层变厚时原岩应力的分布特征、爆炸应力波在构造煤岩体中的传播过程,并结合相似模拟实验与数值模拟研究了爆破载荷作用下煤厚变异区的损伤破坏特征。理论分析表明,薄煤层区域承受的原岩应力高于厚煤层,且应力变化梯度随煤厚减小率的增大而增大,爆炸应力波由岩体传播至构造煤体时会发生波的透射和反射现象,反射形成的拉伸波将加剧煤岩交界面岩体侧的损伤程度;爆破模拟实验中采集得到的应力曲线,煤厚变异区岩体处的测点存在着2次较大的拉应力峰值,应力波在该处相互作用形成了叠加破坏区,破坏区同时又引导其余方向的爆生裂纹向其延伸汇集,导致岩体严重破坏。数值模拟验证了爆炸应力波在煤岩交界面上的透射和反射现象,应力云图表明应力波在煤厚渐变区的叠加作用最明显且延续时间长。研究成果对于揭示爆破扰动煤厚变异区诱发煤与瓦斯突出的机制有重要指导意义。

Aiming at the fact that coal and gas outbursts are easily induced in regional blasting construction of geological structures,an elastic mechanical model of coal and rock combination was established.Based on propagation and action laws of blast stress waves in coal and rock medium,distribution features of the original rock stress during coal seam thickening and propagation process of explosion stress waves in tectonic coal rock mass were analyzed.Using similar analog tests combined with numerical simulations,the damage and failure characteristics of coal thickness variation zones under blast loading were studied.The results of tests and simulations showed that the original rock stress withstood by thin coal seam is higher than that withstood by thick coal seam,and the stress change gradient increases with increase in coal thickness reduction rate;when blast stress waves propagate from rock body to tectonic coal body,wave transmission and reflection phenomena occur;the reflection-induced tensile wave aggravates the damage level of rock body side of coal-rock interface;stress curves acquired from blast analog tests indicate,the stress waves mutually act to form a superposed failure zone at the rock body of the coal thickness variation area,the failure zone makes blast-induced cracks in other directions extend to it and gather to cause serious failures of the rock body,the tensile stress in the failure zone has 2 larger peak values;the numerical simulations verify transmission and reflection phenomena of blast stress waves at the interface of coal and rock;the stress cloud diagram indicates,the superposition action of stress waves in the coal thickness transition region is the most obvious and lasts long time.The study results provided a meaningful guide for revealing the mechanism of blasts to disturb a coal thickness variation area and induce coal and gas outbursts.