基于FDEM的围压条件下机械冲击破岩机理研究

Rock breaking mechanism with mechanical impact under confining pressure based on FDEM

矿产资源的开采越来越趋向深部发展,而深部围岩往往处于高应力状态下。岩石作为一种主要由矿物颗粒构成的非均质材料,其矿物颗粒间的细观力学性质会对机械冲击破岩行为造成极大的影响,因此有必要考虑围压和岩石细观力学性质对机械冲击破岩行为的影响。首先,采用有限元-离散元(FDEM)方法,在ABAQUS有限元模型全域内嵌入零厚度黏聚力单元,模拟深部高应力条件下的机械冲击破岩过程;然后,通过室内单轴压缩和巴西劈裂试验进行算法验证和参数标定;最后,建立相应的冲击破岩FDEM模型,并定量分析围压和细观力学参数(断裂能、细观强度、接触刚度比)对冲击破岩行为的影响规律。研究结果表明:在高围压下,岩石会出现岩爆现象,破岩效果明显提高;岩石的断裂能和细观强度增加均会导致破岩效果降低,其中断裂能越大,岩石产生岩爆现象的难度越高;降低细观强度会减小发生岩爆的围压;接触刚度比越大,冲击破岩过程越容易发生岩爆现象。

The mining of mineral resources tends to develop deeper and deeper surrounding rock,which is often under high stress.As a non-homogeneous material mainly composed of mineral particles,the micromechanical properties of rock can greatly affect the macromechanical behaviors of rock.It is necessary to consider the influence of confining pressures and micromechanical properties of rock on impact-induced rock breaking behavior.Firstly,the finite-discrete element(FDEM)method was used to simulate mechanical impact induced rock breaking under deep high stress condition by embedding zero-thickness cohesive elements in the ABAQUS finite element model.Secondly,the uniaxial compression and Brazilian splitting tests were used to verify the algorithm and calibrate the parameters.Finally,the corresponding FDEM model of impact-induced rock breaking was developed,and the influences of confining pressure and micromechanical parameters(fracture energy,microscopic strength and contact stiffness ratio)on impact-induced rock breaking behavior were quantitatively analyzed.The results show that rockburst phenomenon will occur under high confining pressure,and the corresponding rock breaking efficiency will be significantly improved.The rock breaking efficiency decreases with the increase of fracture energy and microscopic strength.The larger the fracture energy is,the more difficult it is for the rockburst.The confining pressure of appearing rockburst decreases with the decrease of microscopic strength.In addition,the larger the contact stiffness ratio is,the easier it is for the impact rock breaking process to present rockburst phenomenon.