Experimental analysis and characterization of damage evolution in rock under cyclic loading
Experimental analysis and characterization of damage evolution in rock under cyclic loading
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循环荷载下岩石损伤演化的实验分析与表征
DOI：
10.1016/j.ijrmms.2016.07.015
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发表时间：
2016-10-01
影响因子：
7.2
通讯作者：
Zhang, Qian
中科院分区：
文献类型：
--
作者：
Song, Haipeng;Zhang, Hao;Zhang, Qian
在地下开挖、岩石边坡和采矿等岩石工程领域中，岩石材料经常会经历循环荷载作用。由于岩石固有的微观结构，岩石在重复应力作用下的力学性质和破坏过程与静载作用下有很大的不同。1，2，3因此，研究岩石在循环荷载作用下接近破坏的损伤演化过程具有重要意义，因为这样的研究有助于更好地理解岩石的损伤和破坏机理，以解决实际工程问题。在过去的几十年里，人们对复杂载荷作用下岩石的损伤与破坏进行了一些理论研究。谢等讨论了循环荷载作用下岩石破坏过程中能量耗散、能量释放与强度之间的关系。4基于细观力学理论，预测了含多个相互作用微裂纹的脆性固体的有效性质。5.根据岩石轴向不可逆变形发展规律，建立了倒S型非线性疲劳损伤累积模型。为了研究岩石的力学特性，还进行了许多循环载荷试验。宏观试验清楚地表明，循环加载导致岩石7、8的逐渐弱化，并且表明单轴抗压强度随着施加的应力水平和加载循环次数的增加而减弱。9.试验分析了加载频率和围压条件对循环加载下砂岩试样强度和变形特性的影响。10，11此外，不同类型的实验技术，如光学和声学，被用于观察岩石材料在加载过程中的破坏过程。例如，用荧光显微镜观察了博胡斯花岗岩在循环荷载作用下新微裂纹的萌生和扩展。[12]利用干涉测量技术记录了循环荷载期间积累的大应变对大理石造成的损害。13利用透射超声波对承受单轴循环载荷的邦纳湖灰色花岗岩圆柱体中微裂纹损伤的发展进行了评估。14岩石破坏试验中的裂纹活动通过声发射（AE）技术进行监测，工作表明裂纹活动沿着循环次数的增加而增加。然而，循环加载对岩石损伤演化的影响仍然不是很清楚，如何有效地表征基于实验工作的损伤和破坏过程仍需要进一步研究。在众多的实验方法中，数字图像相关技术（digital image correlation，DIC）是一种有效的获取材料表面位移场和应变场的方法，具有全场、实时、在线、动态等优点，和非接触测量以及技术的灵活性。16，17，18，19该方法已广泛应用于各种材料，如金属箔，20，21复合材料，22铝合金的Portevin-Le Chatelier带，23，24和多孔碳酸盐。此外，利用DIC观察了岩石在不同载荷下的变形演化和裂纹发展。26，27，28，29，30，31，32，33，34，35，36，37 Ma等人定义了DIC应变场的标准差作为损伤变量来描述损伤。
In many rock engineering fields such as underground excavation, rock slope and mining activities, rock materials often experience cyclic loading. Due to the intrinsic micro-structure of rocks, the mechanical properties and the failure process under repeated stress differ enormously from those under static loads. 1, 2, 3 Thus, the study of the damage evolution of rocks that approach failure when subjected to cyclic loading is significant because such a study can help to better understand the damage and failure mechanism of rocks for practical engineering problems. In the past decades, some theoretical work on rock damage and failure under complex loading has been developed. Xie et al. discussed the relationship among energy dissipation, energy release and strength during failure process of rock under cyclic loading. 4 Based on micromechanics, the effective properties of brittle solids with numerous interacting microcracks have been predicted. 5 An inverted S-shaped nonlinear fatigue damage cumulative model was derived based on the law of axial irreversible deformation development of rock. 6 Many experimental cyclic loading tests have also been conducted to investigate the mechanical behavior of rocks. Macro tests clearly demonstrated that cyclic loading leads to the progressive weakening of rocks 7, 8 and showed that the uniaxial compressive strength weakens with the increase in the applied stress level and the number of loading cycles. 9 The effects of loading frequency and confining pressure conditions on the strength and deformation characteristics of sandstone sample subjected to cycling loading were also experimental analysed. 10, 11 In addition, different types of experimental techniques, such as optics and acoustics, were used to observe the failure process of rock materials during loading. For example, fluorescent microscopy was used to observe the initiation and propagation of new microcracks in bohus granite under cyclic loading. 12 Damage to marble induced by large strains accumulated during cyclic loading was recorded using the interferometric technique. 13 Transmitted ultrasonic waves were used to assess the development of microcrack damage in a cylinder of Lac du Bonnet gray granite subjected to uniaxial cyclic loading. 14 The crack activities in rock failure tests were monitored via the acoustic emission (AE) technique, and the work indicated that crack activities increases along with an increase in the cycle number. 15 However, the influence of cyclic loading on damage evolution of rock remains not very clear, and how to effectively characterize the damage and failure process based on experimental work still need to be further investigated. As a result, it is necessary to analyze the damage evolution during the entire cyclic loading process, especially using the full-field measurement technique and corresponding experimental analysis method.Among the types of experimental methods, digital image correlation (DIC) is an effective method for obtaining the displacement and strain fields on the surface of materials, with the advantages of providing full-field, real-time, online, and non-contact measurements as well as flexibility in the technique. 16, 17, 18, 19 The method has been extensively applied to various materials, such as metallic foil, 20, 21 composite, 22 the Portevin-Le Chatelier bands of aluminum alloy, 23, 24 and porous carbonate. 25 Moreover, the deformation evolution and crack development of rocks under different loadings were observed using DIC. 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 Ma et al. have defined the standard deviation of the DIC strain field as the damage variable to describe the damage …