Simulating damage evolution and fracture propagation in sandstone containing a preexisting 3‐D surface flaw under uniaxial compression

Mondal, Sanjib; Olsen-Kettle, Louise; Gross, Lutz

doi:10.1002/nag.2908

Cited by 34 publications

(14 citation statements)

References 59 publications

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“…Some numerical simulation results were also reported, which is consistent with the previous experimental results [23,24]. Meanwhile, the effect of physical parameters of the 3D crack on its growth has been studied, including the number of the 3D cracks and geometry shape, and corresponding research also obtained many meaningful results [25][26][27][28][29][30][31][32][33][34][35].…”

Section: Introductionsupporting

confidence: 81%

Research on the Behavior and Mechanism of Three‐Dimensional Crack Growth under Uniaxial Loading

Zhang

Qin

2021

Advances in Materials Science and Engineering

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Most of the cracks in the rock masses are in a three-dimensional (3D) state, and it is always a hot topic to reveal the mechanical mechanism of 3D crack growth. In this paper, the research on the growth behavior of 3D crack is performed through laboratory experiments and numerical simulations. Cement samples with different angles of 3D crack are prepared, and the uniaxial compression experiment is carried out. The results indicate that initiation of preexisting crack with an angle of 45° is easier and shear failure characteristics of corresponding samples are obvious. Through theoretical analysis, the preexisting crack starts to grow at the end of the short axis, along the short axis end to the long axis end of the preexisting crack, the shear effect decreases gradually, and the tearing effect increases gradually. Combined with numerical simulation, the experimental and analysis results are verified, and the preexisting crack growth process is presented. The growth direction of the preexisting crack changes from perpendicular to the crack surface to parallel principal stress direction, and the maximum growth length can reach 1.2 times the minor axis radius of the preexisting crack. The research results can provide an important theoretical basis for revealing the evolution process of the cracks in rock masses.

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Section: Introductionsupporting

confidence: 81%

Research on the Behavior and Mechanism of Three‐Dimensional Crack Growth under Uniaxial Loading

Zhang

Qin

2021

Advances in Materials Science and Engineering

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“…The simulation of granites with prefabricated joints by PFC shows that granites usually generate tensile fracture with low confining pressure, tensile-shear mixed fracture with medium confining pressure, and shear fracture with high confining pressure [14]. The simulated crack growth, coalescence, and type are highly consistent with the experimental results by using the method of finite element with unstructured mesh of tetrahedral element [15]. Simultaneously, there is also research on the mechanical properties and expansion modes of granite with two kinds of joints.…”

Section: Introductionsupporting

confidence: 65%

Experimental Study on Influence of Chemical Corrosion on Mechanical Property of Fissured Granite

Zhang

JunjieKang

et al. 2021

Geofluids

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The effect of chemical corrosion and natural joints on the damage characteristics and strength of rock masses is highly important for the construction of rock engineering and energy extraction. Therefore, the intact granite is processed into prefabricated fissured granite specimens with a fissure angle of 0°, 30°, and 45°. Chemical corrosion tests are then performed on the prefabricated fissured granites. The pH of the solution gradually becomes neutral; the mass loss of the granite specimens and the mineral compositions of the fissure surface are measured and analyzed. The scanning electron microscopy (SEM) and uniaxial compression tests are performed on the granite specimens after chemical corrosion. After chemical corrosion, the surface of the fissure becomes loose. The various mineral components of the specimens have been changed to different degrees or converted into other mineral components. The peak strength and elastic modulus of the prefabricated fissured granites with the three fissure angles present a clear decrease, as the time of chemical corrosion increases. The stress intensity factors at the fissured tip are also analyzed. The stress intensity factors of the specimens with a fissure angle of 0°, 30°, and 45° decrease from 0.017, 0.35, and 0.84 to 0.013, 0.30, and 0.74 MPa·m1/2, respectively, as the time of the chemical corrosion increases. And the chemical corrosion has the largest effect on the intensity factors of the specimens with a fissure angle of 45° among the three angles. These experimental results could improve the understanding of the long-term stability of underground engineering in the multifield coupling environment.

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“…The length of the pre-existing flaw has a big impact on damage studied by Mondal et al [16]. We study flaw lengths ranging from 20, 30, 40 and 50 mm; with flaw depth and flaw angle fixed at 8 The results shown in this chapter have both similarities and dissimilarities with the results of Chapter-3 as well as with experimental results [15].…”

Section: Variation Of Flaw Lengthmentioning

confidence: 72%

“…and 6 have been written as "stand-alone" research articles for local and non-local damage models respectively. Chapter-3 has already been published in the International Journal for Numerical and Analytical Methods in Geomechanics [16]. A more detailed summary of the content of each chapter is given bellow.…”

Section: Thesis Structurementioning

confidence: 99%

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Numerical modelling of damage evolution and fracture propagation in brittle materials

Mondal¹

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The understanding of damage evolution and fracture propagation in rocks as a brittle material is important for many industrial applications; for instance to investigate mine safety, to analyze material failure in manufacturing and construction and to understand the behaviour of pre-existing fractures on hydraulic fracturing in oil and gas extractions. Currently, numerical studies for fracture propagation in brittle rock specimens with pre-existing fractures show strong mesh dependence. To address the issue of mesh independence, further numerical investigation and improvement of damage models under a fully 3-D assumption is critical.In this thesis, we develop numerical tools to investigate the effect of model parameters, including the heterogeneity of rock by allowing Young's modulus to vary spatially, and of the geometry of a pre-existing fracture on the stress-strain response and damage evolution in rocks. The fracture propagation model uses continuum damage mechanics where the elastic modulus reduces with damage as the rock is weakened through the formation of fractures. Two failure conditions are presented, a micromechanical model [1,2] using the unified strength theory [3,4] and a strain-based form of a modified von-Mises condition [5]. Various damage evolution laws are considered which can simulate a range of behaviour from brittle to quasi-brittle. Four different damage evolution laws are analyzed for a 3-D rectangular single flaw specimen to deliver the most realistic results. The quasi-static equilibrium equation is solved for various cases of brittle failure and damage evolution for specimens under loading using the Finite Element Method (FEM) with tetrahedron elements on unstructured meshes. In contrast to previous implementations based on rectangular grids, the use of unstructured meshes provides higher geometrical flexibility and allows a more accurate way of including geological features, such as flaws, through locally adapted (FEM) meshes.An important factor affecting the mechanical behaviour during the failure process is the heterogeneity of the rock. Heterogeneity is simulated by sampling the initial local Young's modulus from a Weibull distribution over a cubic grid. The values are then interpolated to the computational (unstructured FEM) mesh. This approach introduces an additional length scale for rock heterogeneity represented by the cell size in the sampling grid that is independent of FEM mesh size. This approach is different from previous implementations of rock heterogeneity [6][7][8] where the length scale is determined by the mesh resolution.A well-known problem which arises in "local" damage models is that they suffer from mesh dependency [2] and strain localization [9]. In this work, we apply the non-local implicit gradient damage formulation of Peerlings et al.[5] to address the issue of mesh dependency. The basic concept of the non-local implicit gradient model is that the strain at a given point depends not only on the strain at that point but also on the nearby strain field. The lo...

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Simulating damage evolution and fracture propagation in sandstone containing a preexisting 3‐D surface flaw under uniaxial compression

Cited by 34 publications

References 59 publications

Research on the Behavior and Mechanism of Three‐Dimensional Crack Growth under Uniaxial Loading

Research on the Behavior and Mechanism of Three‐Dimensional Crack Growth under Uniaxial Loading

Experimental Study on Influence of Chemical Corrosion on Mechanical Property of Fissured Granite

Numerical modelling of damage evolution and fracture propagation in brittle materials

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