Energy evolution and failure characteristics of red sandstone under discontinuous multilevel fatigue loading

Ju, Wang; Shi, Zhanming; Chen, Jinci

doi:10.1016/j.ijfatigue.2022.106830

Cited by 28 publications

(8 citation statements)

References 49 publications

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“…In the cyclic loading and unloading test, the various energies generated during each cycle can be calculated by the image integration method(Wang et al., 2022a). A schematic diagram of the calculation of the hysteretic energy and elastic energy of the rock is shown in Figure 13.…”

Section: Damage Modeling and Analysismentioning

confidence: 99%

Fracture behavior and damage evolution model of sandstone containing a single pre-existing flaw under discontinuous fatigue loading

Shi

et al. 2022

International Journal of Damage Mechanics

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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.

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Section: Damage Modeling and Analysismentioning

confidence: 99%

Fracture behavior and damage evolution model of sandstone containing a single pre-existing flaw under discontinuous fatigue loading

Shi

et al. 2022

International Journal of Damage Mechanics

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“…Duan, Ji [ 20 ] used granite to carry out laboratory tests, and radial unloading tests showed that radial strain played a major role in the change of bulk strain during unloading. Wang, Li [ 21 ] explored the energy storage and conversion characteristics of sandstone in the process of discontinuous loading and unloading, and explained the strength law of rock from the perspective of energy. Rong, Li [ 22 ] found that different aspect ratios would affect the failure mechanism of rock mass during unloading, and that an increase in aspect ratio would change the failure mode of rock from splitting failure to tensed shear failure.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Shear Behavior of Rock Composite Material under Normal Unloading Conditions

et al. 2023

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As a composite material, the stability of rock mass is usually controlled by a joint. During the process of excavation, the normal stress of the joint decreases continuously, and then the shear strength of the joint decreases, which may eventually lead to the instability and failure of rock mass. Previous studies have mainly focused on the shear behavior of joints under constant normal stress, but have rarely considered the unloading of normal stress. In this paper, a direct shear test of joints with different roughness was carried out, in which the shear stress remained unchanged while the normal stress decreased. The strength characteristics of joints were explored, and the deformation and acoustic emission-counting characteristics of joints were analyzed by digital image correlation (DIC) techniques and acoustic emission (AE). A new method for predicting the instability of joints under normal unloading was proposed based on the evolution law of normal deformation energy (Un), tangential deformation energy (Us) and total deformation energy (U0). The results show the following: (1) The unloading amount of normal stress was enlarged for greater initial normal stress and roughness, while it decreased with an increase in initial shear stress. (2) AE events reached their maximum when the normal stress was equal to the failure normal stress, and the b-value fluctuated more frequently in stable development periods under normal unloading conditions. (3) U0 would change with the loading and unloading of stress, and this may be used to predict the unloading instability of rock mass using the abrupt change of U0.

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“…One of such undertakings is substitution of the OPC part in the composition of the concrete mix with other mineral materials [31][32][33][34]. In most cases, they are waste from various industrial processes [35][36][37][38][39] and are referred to as Supplementary Cementitious Materials (SCMs) [40][41][42][43]. It should also be noted that concretes made with the participation of SCMs allow not only to reduce CO 2 emissions generated during the burning of the Portland clinker [44,45], but also significantly reduce the amount of energy necessary to carry out this technological process [46].…”

Section: Introductionmentioning

confidence: 99%

Examination of water absorption of low volume fly ash concrete (LVFAC) under water immersion conditions

Golewski

2023

Mater. Res. Express

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The studies were carried out to find a relation between important physical property and the main mechanical parameter of concretes containing fly ash (FA) in order to develop indications for the production of durable composites with the addition of this waste. The tests included low volume fly ash concrete (LVFAC). The cements used in the studies were following: ordinary Portland cement (OPC), (FA-00) and two blended Portland cements containing FA in the amount of: 20%, (FA-20) and 30% (FA-30). Measurements of water adsorption (wa) by immersion and compressive strength (fcm) of analysed composites have been performed. The methodology of the wa tests was to reflect the conditions prevailing in the case of concrete- and reinforced concrete structures operating below the water table. The microstructure of all three materials was also assessed. Test results indicated that LVFAC mixes developed 28-day fcm between 45.10 for FA-30 to 48.96 MPa for FA-20 with a value of 47.51 MPa for the reference concrete. Neverless wa of LVFAC mixes decreased with the increase in FA content. The average values of wa was 4.6% for FA-30 and 5.3% for FA-20, respectively, while for concrete without FA it was 5.0%. Thus, it was found that wa by immersion was inversely proportional to the fcm. Based on the microstructural studies it was found that this behavior is attributed to reduced pore diameters and densification of cement matrix microstructure in FA-30 concrete. On the other hand concrete of series FA-20 showed a loose and porous microstructure, and wa in this composite increased accordingly. It can be stated that, the LVFAC containing 30% FA may increase durability of reinforced concrete structures subjected to immersion conditions.

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Energy evolution and failure characteristics of red sandstone under discontinuous multilevel fatigue loading

Cited by 28 publications

References 49 publications

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

Experimental Study on Shear Behavior of Rock Composite Material under Normal Unloading Conditions

Examination of water absorption of low volume fly ash concrete (LVFAC) under water immersion conditions

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