含水平裂隙的3D打印类岩石试件力学特性研究

Study on the Mechanical Properties of 3D Printed Rock-Like Specimens Containing a Horizontal Flaw

为探究裂隙张开度对裂隙岩体力学特性的影响机制,利用3D砂型打印技术制备含水平裂隙的类岩石试件,考虑不同的裂隙张开度,对其进行单轴压缩试验;通过有限元数值模拟从应力分布的角度解释试验现象;结合数字图像相关方法进行非接触式全场变形观测,定量分析裂纹萌生、扩展以及贯通行为。研究结果表明:通过3D砂型打印技术制备的裂隙类岩石试件具有更接近于天然岩石的物理力学特性,且试验结果具有很好的可重复性,测试所得的力学参数变异系数小于0.046;含不同水平裂隙张开度的类岩石试件应力■应变曲线大致相似,峰值强度随着裂隙张开度的增加而逐渐减小,最后趋于稳定;裂隙张开度的增加导致试件起裂应力逐渐增大,但裂纹均起裂于裂隙中部,这与主应力最大值及其分布位置有关;数字图像相关方法可实现试件加载过程的应变全场测量,应变局部化带的渐进演化反映了裂纹起裂、扩展以及贯通行为;计算裂纹扩展路径周边的位移矢量分布,识别出张拉、剪切、拉剪3种位移场类型,发现裂隙张开度的改变不会影响试件破坏模式,均表现为拉剪混合破坏。研究有助于进一步加深裂隙岩体力学特性的认识,也为3D打印技术在岩石力学试验的应用提供参考。

In order to explore the influence of flaw aperture on the mechanical properties of fractured rock mass,the specimens containing a horizontal flaw were prepared by 3 D sand printing,and different flaw apertures were considered.The uniaxial compression tests were performed.The experimental phenomenon was explained from the perspective of stress distribution by using the finite element numerical simulation.The digital image correlation method was used to monitor the full-field deformation during loading with non-contact to quantitatively analyze the crack initiation,propagation and coalescence.The results show that:The mechanical properties of 3 D sand printing rock-like specimen are similar to those of natural rock,the experimental results also have well repeatability,and the variation coefficients of mechanical parameters are less than 0.046;the stress-strain curves of rock-like specimens with different flaw apertures are similar.The peak strength gradually decreases with the increase of flaw apertures and finally tends to be stable.A larger flaw aperture leads to a higher crack initiation stress.The crack firstly initiates in the middle of the pre-existing flaw,which is attributed to the maximum value of principal stress and corresponding distribution;the digital image correlation method was used to monitor the full-field deformation of the specimens during loading,progressive evolution of strain localization is observed in the process of deformation and fracturing,which reflects the law of crack initiation,propagation and coalescence.By calculating the displacement vector distribution around the crack propagation path,three types of displacement fields are identified:tensile,shear and tensile-shear mixed,it is found that the flaw aperture does not affect the failure mode of the specimens,which can be characterized by the tensile-shear mixed failure.This study can further improve understanding of the mechanical properties of fractured rock masses,and provides a reference for the application of 3 D printing technology in rock mechanics.