层理角度对天然岩石材料动态断裂行为的影响研究

Effect of bedding angle on dynamic fracture behavior of natural rock materials

为了探究不同层理角度下岩石材料的动态断裂行为,利用分离式霍普金森压杆冲击加载系统,对3种直切槽半圆岩石试件开展30°,45°,60°,75°和90°层理角度梯度内的动态断裂冲击试验,研究3种岩石试件在不同层理角度条件下的应力波及能量传播规律、应力响应特征和动态断裂韧性。并结合DLSM数值模拟软件进行辅助分析,证明其模拟方法能够较好地应用于岩石动态断裂行为的研究,通过应力波传播图像和裂纹尖端应力场图像分析试件应力波的传递规律,解释动态断裂韧性随层理角度改变的机制。结合模型的动能和破坏曲线总结不同层理角度下岩石的破坏特征。结果表明:层理角度改变会影响层理面对应力波的有效反射面积,从而影响反射波和透射波的传递规律,造成各部分能量比值的变化。3种岩石具有不同的破坏特征,但其动态断裂韧性均受到层理角度的影响,在小层理角度时更容易发生预裂和张拉破坏,导致试件强度降低。模拟得到的应力波传播图像解释了不同层理角度应力波的透反射规律,而裂纹尖端应力场图像则反映了动态断裂韧性与试件内部是否发生提前破坏有关。随着层理角度的增大,试件断裂消耗的动能越大,其破坏更具有均匀性。

In order to explore the dynamic fracture behavior of rock materials under different bedding angles,the dynamic fracture impact test were carried out on three kinds of notched semi-circular bend rock specimens in 30°,45°,60°,75°and 90°bedding angles using the split Hopkinson pressure bar impact loading system.The stress wave and energy propagation law,stress response characteristics and dynamic fracture toughness of the three rock specimens under different bedding angles conditions were studied.DLSM numerical simulation software is used to assist analysis,which proves that the simulation method can be well applied to the study of rock dynamic fracture behavior.Stress wave propagation images and crack tip stress field images are used to analyze the stress wave transmission law of specimens,and explain the mechanism of dynamic fracture toughness changing with the bedding angle.Combined with kinetic energy and failure curves of the model,failure characteristics of rocks under different bedding angles are summarized.The results show that the change of bedding angle will affect the effective reflection area of the stress wave,and thus affect the transfer law of reflected wave and transmitted wave,resulting in the change of the energy ratio of each part.The three kinds of rocks have different failure characteristics,but their dynamic fracture toughness is affected by the bedding angle,and precracking and tensile failure are more likely to occur at small bedding angle,leading to the reduction of specimen strength.The simulated stress wave propagation image explains the transreflectance law of stress waves at different bedding angles,while the stress field image of crack tip reflects that the dynamic fracture toughness is related to the occurrence of premature failure in the specimen.With the increase of the bedding angle,the larger the kinetic energy consumed by the fracture of the specimen,the more uniform the failure.