Fracture behavior and damage evolution model of sandstone containing a single pre-existing flaw under discontinuous fatigue loading
Fracture behavior and damage evolution model of sandstone containing a single pre-existing flaw under discontinuous fatigue loading
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非连续疲劳载荷下含单一缺陷砂岩断裂行为及损伤演化模型
DOI：
10.1177/10567895221123090
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发表时间：
2022-09
影响因子：
4.2
通讯作者：
Z. Shi;Jiangteng Li;Ju Wang;Jinci Chen
中科院分区：
文献类型：
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作者：
Z. Shi;Jiangteng Li;Ju Wang;Jinci Chen
深部岩体工程灾害孕育过程主要与岩体的断裂行为和损伤机制有关。本文提出了一种基于改进Harris分布的等效应变假设和实验室非连续疲劳试验的损伤模型。首先，对节理砂岩试件进行了非连续疲劳加载试验，并利用声发射技术进行了研究。基于b值和AF-RA理论，从裂纹演化过程和裂纹分类两个方面对试件的破坏模式进行了进一步探讨。同时，利用数字图像相关技术（DIC）分析了试件表面变形场的演化过程。随后，通过扫描电子显微镜（SEM）技术，从微观角度分析了岩体的断裂形态特征。研究发现，在短时间内，低水平恒载会导致岩体内部颗粒互锁，耦合损伤增量减小，塑性增强，”伴随“耦合损伤增量减小和塑性增强，从而抑制损伤扩展速率。此外，随着应力水平的增加，晶粒间摩擦加剧，断口切屑和粗糙度增加，疲劳软化效应增强，试件逐渐由脆性破坏向韧性破坏转变。同时，应力诱发的拉伸裂纹和剪切裂纹所占比例逐渐增大，导致试件最终呈现拉剪复合破坏。
The process of disaster incubating in deep rock mass engineering is mainly related to the fracture behavior and damage mechanism of the rock mass. This paper proposes a new damage model based on Lemaitre's equivalent strain hypothesis with improved Harris distribution and laboratory discontinuous fatigue loading test (DFLT). Firstly, discontinuous fatigue loading tests were carried out on the jointed sandstone specimens and acoustic emission (AE) was used as a research tool. Based on the b-value and AF-RA theory, the failure mode of specimens was further explored in terms of the crack evolution process and crack classification. Meanwhile, digital image correlation (DIC) techniques were used to analyze the evolution of the deformation field on the surface of the specimen. Subsequently, the fracture morphological characteristics of the rock masses were analyzed from a microscopic perspective by scanning electron microscopy (SEM) techniques. The investigations found that in a short time, the low-level constant load will lead to the interlocking of particles inside the rock mass, reduced incremental coupled damage, and enhanced plasticity “with” reducing the coupled damage increment and enhancing the plasticity, thereby inhibiting the damage growth rate. In addition, as the stress level increases, the friction between the grains intensifies, the cuttings and roughness of the fracture surface increase, the fatigue softening effect is enhanced, and the specimen gradually transforms from brittle failure to ductile failure. At the same time, the proportion of stress-induced tensile cracks and shear cracks gradually increased, resulting in the specimen finally presenting tensile-shear composite failure.