Experimental Study on the Growth, Coalescence and Wrapping Behaviors of 3D Cross-Embedded Flaws Under Uniaxial Compression

Fatigue Fract Eng Mat Struct

Zhou

et al. 2019

124

Uniaxial compression tests combined with nondestructive testing techniques are performed to explore the roles of non‐isometric flaws in crack developments in brittle rocks. The acoustic emission (AE) rate‐process theory is adopted to analyze fracture‐related AE event rate characteristics. The full‐field optical method is applied to detect cracking modes. Experimental results show that AE activity is quite active when the matrix microcracking is dominant, while after each macrocracking event, AE activity becomes inactive because of the stress release. Multiphysical data for each tested flaw configuration faithfully confirm the rupture progressivity. The larger the flaw length ratio, the lower the peak stress (also peak axial strain and elastic modulus), as well as the more progressive the cracking process. Moreover, ultimate failure is triggered by the shear fracturing from the relatively long flaw. The short flaw is conditionally involved in ultimate failure when the stress buildup effect dominates. Finally, the fracture mechanism of brittle rocks with non‐isometric flaws is revealed.

Section: Stress Evolutions Of Sandstone Specimens With Non-isometrimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Progressive failure of brittle rocks with non‐isometric flaws: Insights from acousto‐optic‐mechanical (AOM) data

Fatigue Fract Eng Mat Struct

Zhou

et al. 2019

124

“…Natural flaws sometimes appear as either threedimensional (3-D) surface flaws or embedded flaws in rock masses. Previous studies 14,15 indicated that 3-D cracking behaviors are significantly different from 2-D cracking behaviors. Yin et al 14 investigated the coalescence mechanism on granite specimens containing two parallel 3-D prefabricating surface cracks using the digital speckle correlation method (DSCM).…”

Section: Introductionmentioning

confidence: 95%

Experimental study on effects of freeze‐thaw fatigue damage on the cracking behaviors of sandstone containing two unparallel fissures

Zhou

Niu

Fatigue Fract Eng Mat Struct

et al. 2019

This paper investigates the effects of freeze‐thaw (FT) fatigue damage on the cracking behaviors of sandstone specimens containing two unparallel fissures under uniaxial compression. First, the effects of FT fatigue damage and fissure angle on the mechanical properties of sandstone specimens are analyzed. Second, the real‐time cracking process of sandstone specimens is captured by a high‐speed digital video camera system. Seven crack coalescence patterns are observed in this experiment. Local strong fatigue‐damaged zones, which are visualized as white zones, are observed in the specimens subjected to FT cycles during loading. Finally, scanning electron microscopy (SEM) observations show that the local strong fatigue‐damaged zones mainly consisted of microcracks and micropores induced by the FT fatigue damage. These experimental results are helpful for improving the understanding of the cracking process in cold‐region engineering.

“…Previous studies on precracked material mainly consisted of the following three categories, namely, experimental tests on rock-like materials, numerical simulation on model specimens, and experimental tests on original rocks. Due to the high efficiency and low cost, rocklike materials have widely been used in many experiments [9][10][11][12][13][14][15]. According to uniaxial compression tests for rock-like materials containing three parallel frictional flaws, Wong et al [16] found that the uniaxial compression strength of the specimens depended on the actual number of preexisting flaws involved in the coalescence.…”

Section: Introductionmentioning

confidence: 99%

Acoustic‐Mechanical Responses of Intact and Flaw‐Contained Rock Deformation under Uniaxial Compression: A Comparison

Wang

Advances in Civil Engineering

Wang

et al. 2019

Self Cite

The study of the mechanical properties and cracking behaviors of jointed rock masses is important in rock engineering projects. In the present study, a series of uniaxial compression experiments were conducted on intact rock, and rock masses with single or double preexisting flaws, and then the strength, deformability, and fracture behavior of samples are investigated. Moreover, photographic monitoring technique and emission monitoring technique are introduced to explore the fracturing mode and the acoustic emission (AE) evolution characteristic of fractured rock during the whole loading process. The obtained results show that the preexisting flaw has a strong influence on the mechanical properties, fracture behavior, and AE characteristic of sandstone specimens. In detail, the stress-strain curves show that no significant stress jump occurs at prepeak and postpeak points for intact sandstone specimens; however, the flaw-contained sandstone specimens exhibit distinct stress jump during the entire loading process. Meanwhile, the strength parameters of the the rock specimen is obviously weakened by the preexisting fissures, and the uniaxial compression strength of rock specimens generally decreases with the increase in the number of preexisting fissure as well as the peak strain and the elastic modulus. The failure modes of intact and flaw-contained sandstone specimens exhibit the splitting failure and the mixed failure modes of shear and tension, respectively. Similarly, the maximum AE counts and AE energy both decrease with the increasing number of preexisting flaw. The present research can enhance the understanding of mechanical properties, cracking behaviors, and failure mechanism of jointed rock mass.