基于DIC的3D打印交叉节理试件破裂机制研究

为研究交叉节理的存在对岩体破裂机制的影响，采用3D打印技术制备了可模拟岩体交叉结构面的节理模型，通过相似材料浇筑形成含预制交叉节理的试件，并基于数字图像相关技术（DIC）分析了单轴压缩下试件裂纹起裂、扩展及破坏模式。研究结果表明：采用3D打印技术制作的闭合节理模型，可以有效替代传统的切割、插缝等方法形成的张开型节理裂隙。基于此展开的试验结果表明，交叉节理存在会显著降低试件强度，且随着交叉角度的增大，试件强度先升高后降低，在45o和60o之间达到最大值，峰值应变与强度呈现相反的变化规律；裂纹扩展过程可分为微裂隙闭合阶段、微破裂发展阶段、主节理起裂扩展阶段和次节理迅速延伸阶段，这与应力?应变曲线各阶段一一对应。研究还发现，在交叉节理岩体中，次节理对破裂的影响主要体现在峰后阶段，结合最大畸变能理论表明，其对主节理尖端应力分布影响较小，主节理对岩体的破坏起绝对控制作用，这对岩体工程有一定的指导意义。

Fracture mechanism of specimens with 3D printing cross joint based on DIC technology

In order to study the influence of the cross joints on the fracture mechanism of rock mass, a joint model that can simulate the cross structural plane of rock mass was prepared by the 3D printing technology. By pouring similar materials, the specimen with prefabricated cross joints was formed. Based on the digital image correlation technology (DIC), the crack initiation, propagation and failure mode of specimen under uniaxial compression were analyzed. The results show that the closed joint model made by 3D printing technology can effectively replace the open joint fissures formed by traditional cutting or slotting methods. The experimental results show that the cross joints can significantly reduce the rock strength. With the increase of the cross joint angle, the strength of specimen increases firstly and then decreases. It reaches the maximum value when the cross joint angle is between 45o and 60o. The peak strain presents an opposite variation rule with that of the rock strength. The process of crack growth can be divided into four stages: the microcrack closure stage, the microcrack development stage, the initiation of main joints and the rapid extension of secondary joints, which correspond to each stage of stress-strain curve. It is also found that the influence of secondary joints on the failure of rock with cross joints is mainly reflected in the post peak stage. Combined with the maximum distortion energy theory, it has little influence on the stress distribution at the tip of the main joints, which play an absolute role in controlling the rock failure. This has a certain guidance for rock engineering.