Anisotropy effect on strengths of metamorphic rocks

Özbek, Ahmet; Gül, Murat; Karacan, Ergun; Alca, Övünç

doi:10.1016/j.jrmge.2017.09.006

Cited by 37 publications

(9 citation statements)

References 38 publications

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“…Its crystal structure varies with direction. Therefore, a variation of P‐wave velocities with direction might be expected for this medium (Özbek et al., 2018).…”

Section: Structural and Geological Settingmentioning

confidence: 99%

Characterizing shallow fault zones by integrating profile, borehole and array measurements of seismic data and distributed acoustic sensing

Rein,

Isken,

Domigall

et al. 2024

Near Surface Geophysics

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Within the framework of the Intercontinental Scientific Drilling Programme (ICDP) ‘Drilling the Eger Rift’ project, five boreholes were drilled in the Vogtland (Germany) and West Bohemia (Czech Republic) regions. Three of them will be used to install high‐frequency three‐dimensional (3D) seismic arrays. The pilot 3D array is located 1.5 km south of Landwüst (Vogtland). The borehole, with a depth of 402 m, was equipped with eight geophones and a fibre optic cable behind the casing used for distributed acoustic sensing (DAS) measurements. The borehole is surrounded by a surface array consisting of 12 seismic stations with an aperture of 400 m. During drilling, a highly fractured zone was detected between 90 m and 165 m depth and interpreted as a possible fault zone. To characterize the fault zone, two vertical seismic profiling (VSP) experiments with drop weight sources at the surface were conducted. The aim of the VSP experiments was to estimate a local 3D seismic velocity tomography including the imaging of the steep fault zone. Our 3D tomography indicates P‐wave velocities between 1500 m/s and 3000 m/s at shallow depths (0–20 m) and higher P‐wave velocities of up to 5000 m/s at greater depths. In addition, the results suggest a NW–SE striking low‐velocity zone (LVZ; characterized by = 1500–3000 m/s), which crosses the borehole at a depth of about 90–165 m. This LVZ is inferred to be a shallow non‐tectonic, steep fault zone with a dip angle of about . The depth and width of the fault zone are supported by logging data as electrical conductivity, core recovery and changes in lithology. In this study, we present an example to test and verify 3D tomography and imaging approaches of shallow non‐tectonic fault zones based on active seismic experiments using simple surface drop weights as sources and borehole chains as well as borehole DAS behind casing as sensors, complemented by seismic stand‐alone surface arrays.

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“…Its crystal structure varies with direction. Therefore, a variation of P‐wave velocities with direction might be expected for this medium (Özbek et al., 2018).…”

Section: Structural and Geological Settingmentioning

confidence: 99%

Characterizing shallow fault zones by integrating profile, borehole and array measurements of seismic data and distributed acoustic sensing

Rein,

Isken,

Domigall

et al. 2024

Near Surface Geophysics

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“…The uneven composition and structure of natural rocks greatly affect their mechanical properties of rocks. Heterogeneity has different influences on the mechanical properties of different types of rocks, such as shale [2], metamorphic rock [4], and sandstone, and also affects the stability of civil engineering, underground mining structure [3] and hydraulic fracturing [9].…”

Section: Introductionmentioning

confidence: 99%

Simulation of Mechanical Test in Digital Rock Affected by Rock Heterogeneity and Flow in Porous Media

Yang²

2023

E3S Web Conf.

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As the main reservoir of oil and gas resources, the physical and mechanical properties of the rock are complicated. The strong heterogeneity of rock and the flow in porous media further influences the nature of stress propagation. Therefore, considering the heterogeneous particle model and fluid-structure coupling, it is very important to study the variation law of rock mechanical properties under a stress state, which lays a foundation for formation fracturing and mining. In this paper, the mechanical properties of the rock are studied by the ideal, heterogeneous, and flow models in porous media. The results show that the stress of the contact surface between particles of the same size is large. Still, the stress of the contact surface between different particles is larger, which is more likely to become the weak mechanical link of failure. When the displacement of the z-axis is the same, the x and y-axis increase the axial stress of the z-axis. The peak stress is high and more sensitive when the particle size difference is small. When water is in the pores, the rock strength obtained under consolidated undrained is greater than that under consolidated drained.

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“…It is commonly believed that rock mass is heterogeneous and discontinuous, containing fissures, joints, faults, cleavage planes, and bedding planes and these structural planes dominate the mechanical behaviors of rock mass [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. Different loading directions concerning structural planes orientations always make rock mass anisotropic and more problematic during engineering construction [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ].…”

Section: Introductionmentioning

confidence: 99%

“…Numerous types of rock mass have inherent or structural anisotropy, such as parametamorphic and sedimentary rocks, and other discontinuity-induced stratiform-like rock masses. Extensive compression tests have been put forward to explore the strength and failure features of various anisotropic rock masses at uniaxial and triaxial compression conditions in the laboratory, e.g., slate [ 18 , 19 , 20 ], schist [ 13 , 20 , 21 , 22 , 23 , 24 ], phyllite [ 13 , 25 ], marble [ 13 , 23 ], sandstone [ 3 ], shale [ 26 , 27 , 28 ], limestone [ 28 , 29 , 30 ], mudrock [ 31 ], columnar basalt [ 32 ], and artificially anisotropic rock specimens [ 3 , 33 ]. Numerical studies have also been conducted to investigate the mechanical behavior of anisotropic rock mass intrinsically [ 12 , 34 ].…”

Section: Introductionmentioning

confidence: 99%

The Confinement-Affected Strength Variety of Anisotropic Rock Mass

Guo

Zheng

et al. 2022

Materials

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It has been recognized that the anisotropic structures dominate the deformation and strength properties of laminated rock masses. The resultant strength anisotropy is strongly affected by confining pressures beyond anisotropic structures. Nevertheless, the effects of confinement are inconsistent among existing experiments and not fully understood. This study focuses on the effects of confining pressure on strength anisotropy through theoretical derivation together with experimental results analysis. The variations in the possibility of anisotropic structural plane dominant failure and strength anisotropy degree under different confining pressures are discussed. The different types of anisotropic structural planes, i.e., the fresh contact discontinuity or soft, thick layer, are found as the key factor resulting in different confinement effects. The strength anisotropy weakens gradually and vanishes eventually as confining stress increases for the anisotropic rock mass with the structural plane of fresh contact discontinuity. On the other hand, the strength does not vanish at very high confining stress and the anisotropic strength difference even rises as confining stress increases for the anisotropic rock mass with the anisotropic structural plane of the soft layer. This study improves the understanding of anisotropic rock mass mechanical behavior, especially at high confining stress, and may promote the development of excavation and supporting techniques for underground projects.

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Anisotropy effect on strengths of metamorphic rocks

Cited by 37 publications

References 38 publications

Characterizing shallow fault zones by integrating profile, borehole and array measurements of seismic data and distributed acoustic sensing

Characterizing shallow fault zones by integrating profile, borehole and array measurements of seismic data and distributed acoustic sensing

Simulation of Mechanical Test in Digital Rock Affected by Rock Heterogeneity and Flow in Porous Media

The Confinement-Affected Strength Variety of Anisotropic Rock Mass

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