长壁回采围岩破损规律的数值模拟研究

Numeric study of damage for the surrounding bed in longwall mining

长壁回采围岩破损规律对于认识地压规律和支护技术具有重要意义.围岩破损的物理实质是微缺陷的形成、扩展和贯通,可以用损伤力学模型描述.根据岩石单轴应力—应变曲线,定义一维损伤变量,唯象地表示岩体单元的破损程度.利用双剪强度理论将一维损伤模型推广到三维损伤模型.数值试验以某大型深埋地下煤矿己15-16-24110长壁回采矿块为对象,模拟回采推进过程中顶、底板岩层的破损发展.结果表明,损伤模型具有非常好的适应性,揭示的围岩损伤规律是:①采空区下部围岩的损伤程度和速度明显高于上部围岩;②在采空区远离工作面的方向,围岩损伤呈周期性振荡上升;③围岩损伤记录了应力作用的历史.

Rock damage evolution in the surrounding bed is very important for strata control in longwall mining. The formation, propagation and through running of microcrack is the physical essence of rock damage, which can be described by the models in rock damage mechanics. One - dimension damage variable is defined based on the stress -strain curve at uniaxial compression and tension. It is a quantitative represent of the extent of damage in the rock element. The theory of double shear strength is used to generalize the one - dimen- sion damage model to three - dimension damage model. The model of numeric test is done in a large size underground coal mine with a mining depth of over 1000 meters. The simulation is to discover the damage evolution in the surrounding bed as the working face advances. The results Show that the damage model in the paper has a good adaptability. And some important rules of the rock damage in the surrounding bed have been con- cluded as these ： ①The damage zone in the underlying stratum of the worked - out section expands more widely, rapidly and deeply in the damage degree than the roof strata, ②In the direction contrary to the working face advances, the damage degree steps up in a form of periodic oscillations, ③The damage in the surrounding bed records the stress history.