Shear Anisotropy Research Articles

The structural, mechanical, thermal, electronic and optical properties of halide perovskites [formula omitted]: First-principles investigations

The structural, mechanical, thermal, electronic and optical properties of inorganic Pb-free double perovskites Cs2TiX6(X=Cl,Br,I) compounds are investigated. Using the first-principles with full-potential linearized augmented plane wave (FP-LAPW) method, supported the density functional theory, and therefore the generalized gradient approximation (GGA-PBE) and Hybrid exchange-correlation functionals with and without spin-orbit coupling. The computation of the lattice constants showed an honest agreement between our results and the experimental results and the theoretical data available. Using the three independent elastic constants C11, C12 and C44, various mechanical and thermal properties are obtained such as: bulk modules B, shear modules G, Young's modules Y, Pough's ratio B/G, Frantesvich ratio G/B, Poisson's ratio υ, Shear anisotropy character A and Debye temperature ΘD for Cs2TiI6, Cs2TiBr6 and Cs2TiCl6 respectively. Our calculated elastic constant results show that Cs2TiI6, Cs2TiBr6 and Cs2TiCl6 are mechanically stable, anisotropic and ductile in nature. Furthermore, the Cs2TiCl6 compound has the highest Debye temperature, which indicates the highest melting temperature. The electronic band structures reveal the semiconductor conductivity of the three compounds, with a band gap suitable for photovoltaic applications, within the range of 1.5–2.96 eV. Finally, Cs2TiCl6(X=Cl,Br,I) HPs compounds exhibit excellent optical properties like optical absorption, conductivity and refraction index.

Undrained basal stability of braced circular excavations in anisotropic and non-homogeneous clays

This paper introduces the plastic stability solutions of braced circular excavations in anisotropic and non–homogeneous clays. Using the framework of Finite Element Limit Analysis (FELA) under axisymmetric conditions, the upper bound (UB) and lower bound (LB) solutions of the stability of excavations can be obtained. The clay is set to be anisotropic, where the Anisotropic Undrained Shear (AUS) model is used as a failure criterion of the surrounding soil. The results of this study are the proposed stability number which is the normalized parameter of the maximum unit weight and the anisotropic undrained shear strength of clay. Four dimensionless parameters are considered in the study: the anisotropic strength ratio, the depth–radius ratio, the depth–embedment ratio, and the strength gradient ratio. The impact of all considered dimensionless parameters on the results of the FELA solutions is examined. A machine learning regression approach, Multivariate Adaptive Regression Splines (MARS), is employed to develop an empirical design equation to predict the stability number of braced circular excavations in anisotropic and non–homogeneous clays. The proposed MARS equation can be a useful and reliable equation to estimate the basal stability of this excavation problem in practice.

Novel relationship between shear and energy density at the bounce in nonsingular Bianchi I spacetimes

In classical Bianchi I spacetimes, underlying conditions for what dictates the singularity structure---whether it is anisotropic shear or energy density, can be easily determined from the generalized Friedmann equation. However, in nonsingular bouncing anisotropic models these insights are difficult to obtain in the quantum gravity regime where the singularity is resolved at a nonvanishing mean volume which can be large compared to the Planck volume, depending on the initial conditions. Such nonsingular models may also lack a generalized Friedmann equation making the task even more difficult. We address this problem in an effective spacetime description of loop quantum cosmology (LQC) where energy density and anisotropic shear are universally bounded due to quantum geometry effects, but a generalized Friedmann equation has been difficult to derive due to the underlying complexity. Performing extensive numerical simulations of effective Hamiltonian dynamics, we bring to light a surprising, seemingly universal relationship between energy density and anisotropic shear at the bounce in LQC. For a variety of initial conditions for a massless scalar field, an inflationary potential, and two types of ekpyrotic potentials we find that the values of energy density and the anisotropic shear at the quantum bounce follow a novel parabolic relationship which reveals some surprising results about the anisotropic nature of the bounce, such as that the maximum value of the anisotropic shear at the bounce is reached when the energy density reaches approximately half of its maximum allowed value. The relationship we find can prove very useful for developing our understanding of the degree of anisotropy of the bounce, isotropization of the postbounce universe, and discovering the modified generalized Friedmann equation in Bianchi I models with quantum gravity corrections.

3D velocity and anisotropy of the southeastern Tibetan plateau extracted by joint inversion of wave gradiometry, ambient noise, and receiver function

With the deformation pattern of the southeastern Tibetan Plateau remaining controversial, its anisotropic structure and the three-dimensional (3D) velocity model are powerful tools for understanding this issue. The surface wave dispersion curve (DC) and receiver function (RF) are sensitive to absolute velocity and elasticity contrasts, respectively. In this work, we propose a new method for the joint inversion of 3D shear velocity (Vs) and anisotropy using the datasets of RFs and DCs, which are obtained by combining the wave gradiometry method and ambient noise tomography. Because DCs and RFs are divided into back-azimuth bins, and both datasets in each bin are jointly inverted to obtain velocity in the corresponding direction, the method is called the azimuth-dependent joint inversion method. By applying this new method to the Temporary West Sichuan Array, we obtained a high-resolution 3D Vs model and anisotropic structure of the southeastern Tibetan Plateau. In our model, the vertically consistent fast propagation direction in the Songpan-Ganzi block (SGB) and the north Chuandian block (NCDB) suggest that the deformation in this region is largely coupled vertically. Our model provides anisotropic evidence of the Yangtze crystalline basement extending to the SGB. The low-velocity zone (LVZ) was much thicker and more prominent in the NCDB than in the SGD. Anisotropy in the middle lower crust of the NCDB does not show any sign of an LVZ flowing from the SGB or the Qiangtang block to the NCDB. These observations are contrary to those of the crust flow model, suggesting that the LVZ was generated locally. The mushroom-shaped high-velocity structure beneath the southern Chuandian block and boundary fault zone may be a relic of the Emeishan paleo-mantle plume.

Dynamical, mechanical, anisotropic, and thermodynamic properties of Mg-XL-Y (XL = Zn, Al) alloys with long-period stacking ordered structures: A first-principles calculation

The dynamical, mechanical, anisotropic, and thermodynamic properties of Mg-XL-Y (XL = Zn, Al) alloys based on three long-period stacking ordered (LPSO) phases (ie, 10H, 14H, and 18R) have been investigated systematically by first-principles calculations. The LPSO phases of Mg-XL-Y (XL = Zn, Al) alloys are thermodynamically, dynamically, and mechanically stable. The each LPSO phase of Mg–Al–Y alloys has superior mechanical properties with larger resistances to deformation under applied stress and shear pressure, stiffness, as well as hardness than those of corresponding to LPSO phases of Mg–Zn–Y alloys. According to universal elastic anisotropic index, percent shear anisotropy, 3D surface structures of Young's moulus, and sound velocities, the LPSO phases of Mg-XL-Y (XL = Zn, Al) alloys exhibit obvious anisotropy. Besides, all LPSO phases of Mg-XL-Y (XL = Zn, Al) alloys possess low lattice thermal conductivity due to the strong anharmonicity. The calculated adsorption energies indicate that the 14H(001) surface of Mg–Al–Y system at the hollow site is more sensitive to absorb O atom.

Elastic Constants of Tetragonal Cu2ZnSnS4 Semiconductor: AB-Initio Calculation

Abstract In this work, an ab-initio calculation is used to investigate the elastic constants and some other mechanical and thermal parameters of tetragonal Cu2ZnSnS4 (CZTS) quaternary semiconducting bulk material in Kesterite (KS) and Stannite (ST) phases. The Quantum Espresso code within the Ultra Soft pseudo potentials (USPP) and the local density approximation (LDA) approach were used in the calculation. Firstly,, studies are started with the prediction of the elastic stiffness constants Cij and the normal and shear anisotropy factors. Then some other mechanical moduli, especially the isotropic bulk modulus B, the shear modulus G, the Young modulus E, the Poisson’s ratio ν, and the Pugh’s criteria (G/B) are delivered. The analysis of the mechanical stability criteria at equilibrium shows that our elastic stiffness constants Cij of CZTS material obey all the stability conditions. Additionally, some other parameters of the CZTS semiconductor, especially: the Vickers hardness HV , the sound velocity, the Debye temperature θD and the melting temperature Tm were also calculated. The obtained values of the elastic constants Cij and other mechanical and thermal parameters agree well with experimental and other theoretical results of the literature. The Debye temperature θD of the KS phase was found at around 332.7 K, and that of the stannite phase was found equal to 329.1 K, respectively.

The magmatic plumbing system of the Acoculco volcanic complex (Mexico) revealed by ambient noise tomography

The GEMex project is a Mexican-European cooperation in geothermal energy focusing on enhancing the Acoculco geothermal system. The volcanic system belongs to the northeastern part of the Trans-Mexican Volcanic Belt. In this study, we present ambient noise seismic tomographies of the anisotropic shear wave velocities and reveal the magmatic plumbing system. The tomographies result from the joint inversion of the multi-mode Rayleigh and Love surface wave velocities and Horizontal to Vertical Spectral Ratios (HVSR or H/V). We also discuss the advantage of this technique compared to traditional ambient noise tomography methods and underline the importance of considering multiple surface wave modes to correctly reveal velocity anomalies buried a few kilometers in depth. A reservoir is identified at about 5 km depth at the northeast outside of the caldera. This reservoir is linked to the south caldera surface via a conduit that follows the caldera's eastern border, mainly the Chignahuapan graben. An intermediate reservoir is also observed at about 2.5 km depth, just below the three most recent monogenetic volcanoes. Results agree well with geological studies, the caldera collapse, its temporal evolution, and other geophysical studies recently reported.

Rheology of marine sponges reveals anisotropic mechanics and tuned dynamics.

Sponges are animals that inhabit many aquatic environments while filtering small particles and ejecting metabolic wastes. They are composed of cells in a bulk extracellular matrix, often with an embedded scaffolding of stiff, siliceous spicules. We hypothesize that the mechanical response of this heterogeneous tissue to hydrodynamic flow influences cell proliferation in a manner that generates the body of a sponge. Towards a more complete picture of the emergence of sponge morphology, we dissected a set of species and subjected discs of living tissue to physiological shear and uniaxial deformations on a rheometer. Various species exhibited rheological properties such as anisotropic elasticity, shear softening and compression stiffening, negative normal stress, and non-monotonic dissipation as a function of both shear strain and frequency. Erect sponges possessed aligned, spicule-reinforced fibres which endowed three times greater stiffness axially compared with orthogonally. By contrast, tissue taken from shorter sponges was more isotropic but time-dependent, suggesting higher flow sensitivity in these compared with erect forms. We explore ecological and physiological implications of our results and speculate about flow-induced mechanical signalling in sponge cells.

Upscaling Shear Strength of Heterogeneous Oil Sands with Interbedded Shales Using Artificial Neural Network

SummaryUnderstanding the shear strength of caprock shale and oil sands is important in risk assessment of slope stability in open-pit mining, caprock integrity of in-situ thermal recovery, and optimization of bitumen production from oil sands. A robust and efficient upscaling technique is essential to model the impact of heterogeneity on the deformation and failure of oil sands and caprock shale. Although conventional analytical and numerical upscaling techniques are available, many of these methods consider oversimplified assumptions and have high computational costs, especially when considering the impact of spatially correlated interbedded shales on the shear strength. A machine learning enhanced upscaling (MLEU) technique that leverages the accuracy of local numerical upscaling and the efficiency of artificial neural network (ANN) is proposed here. MLEU uses a fast and accurate ANN proxy model to predict the anisotropic shear strength of heterogeneous oil sands with interbedded shales. The R2 values of the trained ANN models exceed 0.94 for estimating shear strengths in horizontal and vertical directions. The deviation of upscaled shear strength from numerical upscaled results is improved by 12–76% compared with multivariate regression methods like response surface methodology (RSM) and polynomial chaos expansion (PCE). In terms of computational efficiency, the proposed MLEU method can save computational effort by two orders of magnitude compared with numerical upscaling. MLEU provides a reasonable estimate of anisotropic shear strength while considering uncertainties caused by different distributions of shale beddings. With the increasing demand for regional scale modeling of geomechanical problems, the proposed MLEU technique can be extended to other geological settings, where weak beddings play a significant role and the impact of heterogeneity on shear strength is important.

Undrained Stability of Unsupported Rectangular Excavations: Anisotropy and Non-Homogeneity in 3D

The stability of unsupported rectangular excavations in undrained clay is examined under the influence of anisotropy and heterogeneity using the three-dimensional finite element upper and lower bound limit analysis with the Anisotropic Undrained Shear (AUS) failure criterion. Three anisotropic undrained shear strengths are considered in the study, namely triaxial compression, triaxial extension, and direct simple shear. Special considerations are given to the study of the linearly-increased anisotropic shear strengths with depth. The numerical solutions are presented by an undrained stability number that is a function of four dimensionless parameters, i.e., the excavated depth ratio, the aspect ratio of the excavated site, the shear strength gradient ratio, and the anisotropic strength ratio. To the authors’ best knowledge, this is the first of its kind to present the stability solutions of 3D excavation considering soil anisotropy and heterogeneity. As such, this paper introduces a novel approach for predicting the stability of unsupported rectangular excavation in undrained clays in 3D space, accounting for soil anisotropy and non-homogeneity. Notably, it develops a basis to formulate a mathematical equation and design charts for estimating the stability factor of such type of excavation, which should be of great interest to engineering practitioners.

The structural, mechanical and electronic properties of Ti-Al-based compounds by first-principles calculations.

The first-principles calculations with density functional theory were performed to investigate the effects of transition metal elements (Mo, Cu, Fe, Ni and Nb) on the physical properties of the Ti-Al-based compounds. Our optimized crystal parameters are in good agreement with the previous theoretical and experimental values. The mechanical stability is verified by the independent elastic constants. The B/G and Poisson's ratio ν both show that Al6TiMo is brittle, while other compounds exhibit ductility. The values of compression anisotropy of the compounds are small, but the shear anisotropy of AlCu2Ti and AlNi2Ti is much more intense than that of other compounds. The anisotropy in elastic properties of AlFe2Ti and AlNbTi2 is smaller than that of the others. It can be seen that the capacity to compress along c-axis is smaller than that along a-axis and b-axis for AlNbTi2. For AlNbTi2, the anisotropy of the bulk modulus along a-axis relative to b-axis is more insignificant than that along c-axis relative to b-axis. The hardness and Debye temperature verify that AlFe2Ti has the greatest resistance to the plastic deformation and more intense inter-atomic bonding force, respectively. Band structures and DOS are used to investigate the electronic properties. The band structures without band gaps show that these ternary Ti-Al-based compounds are conductors. DOS shows the interactions between elements and gives the bond properties. Density of states and charge density both show the strong covalent properties of AlFe2Ti by the hybridization between Fe-3d and Ti-3d states.

Reynolds number and submergence ratio effects on turbulence structures in the shallow wake of a horizontal pipe located on a rough bed

The effects of Reynolds number and submergence ratio on mean velocity, separation length, Reynolds shear stresses (RSS), correlation coefficient, anisotropy, and turbulent kinetic energy (TKE) are evaluated by modifying the free-stream velocity and pipe diameter to understand the fluid–structure interaction in the presence of a rough channel bed. Acoustic Doppler velocimetry is used to acquire three-dimensional velocity data in the experiments. The experimental data demonstrate that the non-dimensional separation length is linearly varying with the Reynolds number up to a critical Reynolds number, and after that, it becomes independent of the Reynolds number. The vertical profiles of the mean velocity, RSS, correlation coefficient, anisotropy, and TKE are not affected by the Reynolds number; however, their profiles are affected by the submergence ratio. The RSS and TKE are found to be larger for the higher submergence ratio below the top level of the pipe throughout the wake region. The reattachment point is found to be the most turbulent as the most pronounced peaks of RSS and TKE are occurring at this point. The quadrant analysis reveals that the RSS contribution of ejection events is higher for a lower submergence ratio, whereas the RSS contribution of the sweep events is higher for a higher submergence ratio. In conclusion, this study provides an in-depth understanding of the turbulent flow characteristics in the wake region of a bed-mounted horizontal circular pipe located on a fixed sand bed, especially the modification of the turbulence properties due to changes in the Reynolds number and submergence ratio.

Single‐Crystal Elasticity of Antigorite at High Pressures and Seismic Detection of Serpentinized Slabs

AbstractThe subduction of serpentinized slabs is the dominant process to transport “water” into Earth's mantle, and plays a pivotal role for subduction dynamics. Antigorite, the most abundant serpentine mineral in subduction settings, may imprint a seismic signature on serpentinized slabs, making them seismically distinguishable from the dry, non‐serpentinized ones. However, the complete single‐crystal elasticity of antigorite has not been experimentally constrained at high pressures, hindering the use of seismological approaches to detect serpentinization in subducting slabs. Here, we report the full elastic stiffness tensor of antigorite by single‐crystal Brillouin spectroscopy and X‐ray diffraction up to 7.71(5) GPa. We use our results to model seismic properties of antigorite‐bearing rocks and show that their seismological detectability depends on the geometrical relation between seismic wave paths and foliation of serpentinized rocks. In particular, we demonstrate that seismic shear anisotropy shows low sensitivity to serpentinization for a range of relevant geometries.

Bearing capacity of conical footing on anisotropic and heterogeneous clays using FEA and ANN

The paper presents axisymmetric FEA solutions for the bearing capacity of conical footings embedded in anisotropic and inhomogeneous clays using NGI-ADP model. The bearing capacity factor of conical footings is defined to be a function of three dimensionless parameters: (i) the cone apex angle, (ii) the increasing strength gradient ratio, and (iii) the anisotropic shear strength ratio. A series of parametric studies is carried out to portray the influence of all input parameters on the bearing capacity factors. Based on the FEA results of 216 investigated cases, the artificial neural network (ANN) is adopted to capture the relationship between input parameters and output bearing capacity factors. The complex relationship between input parameters and output bearing capacity is studied through the use of design charts and failure patterns. A new accurate equation with a high value of R2 is proposed and the sensitivity of each input parameter on the output results is scored by adopting the results from the ANN model. This study has provided some practical insights into the performance of conical footings embedded in anisotropic and inhomogeneous clays.

Pronounced Seismic Anisotropy in Kanto Sedimentary Basin: A Case Study of Using Dense Arrays, Ambient Noise Seismology, and Multi‐Modal Surface‐Wave Imaging

AbstractMetropolitan Tokyo is subject to significant seismic hazards because it is located near a triple junction of tectonic plates and because it sits atop the soft and thick sediments of the Kanto sedimentary Basin. Numerical simulations of earthquake ground motions rely on accurate velocity models of the basin elastic and anelastic structure, which remains to be improved. Here, we leverage the density of permanent stations of the Metropolitan Seismic Observation network seismic network to construct a high‐resolution radially anisotropic (VSV ≠ VSH) shear wave velocity model of the Kanto basin. We construct surface waves using ambient seismic noise cross correlations. In sedimentary structures, it is common for several surface‐wave modes to arise and to couple in time, so we use local sub‐arrays to extract the phase velocity of the fundamental mode and first overtone of Rayleigh and Love waves at short periods (1–7 s). We find that a strong and negative shear‐wave anisotropy (−5%) is confined to the upper 300 m depth range, and a strong and positive anisotropy (+5%) at greater depths. We interpret them as a result of the vertical cracks from repeated earthquake damage and sediment stratigraphy in the Kanto Basin. Because anisotropy models are not routinely used in physics‐based ground motion prediction, our study motivates the consideration of seismic anisotropy in sedimentary basins for the ground motion of future earthquakes.

CUSRA2021: A Radially Anisotropic Model of the Contiguous US and Surrounding Regions by Full‐Waveform Inversion

AbstractThe lithospheric structure of the contiguous US and surrounding regions offers clues into the tectonic history, including interactions between subducting slabs and cratons. In this paper, we present a new radially anisotropic shear wave speed model of the upper mantle (70–410 km) of the contiguous US and surrounding regions, constrained by seismic full‐waveform inversion. The new model (named CUSRA2021) utilizes frequency‐dependent travel time measurements, from 160 earthquake events recorded by 5,280 stations. The data coverage in eastern US is improved by incorporating more intraplate earthquakes. The final model exhibits clear and detailed shear wave speed anomalies correlating well with tectonic units such as North America Craton (high‐Vs), Cascadia subduction zones (high‐Vs), Columbia Plateau (low‐Vs), Basin and Range (low‐Vs), etc. In particular, the detailed structure of the North America Craton beneath Illinois basin is revealed. The depth of high‐Vs anomaly beneath the North America Craton correlates well with S‐to‐P receiver function and SH reflection results. Besides, the radial anisotropy in the Craton lithosphere shows a layering structure, which may relate to the process of lithospheric accretion and the origin of mid‐lithosphere discontinuities.

Stress-induced high-Tc superconductivity in solid molecular hydrogen

Solid molecular hydrogen has been predicted to be metallic and high-temperature superconducting at ultrahigh hydrostatic pressures that push current experimental limits. Meanwhile, little is known about the influence of nonhydrostatic conditions on its electronic properties at extreme pressures where anisotropic stresses are inevitably present and may also be intentionally introduced. Here we show by first-principles calculations that solid molecular hydrogen compressed to multimegabar pressures can sustain large anisotropic compressive or shear stresses that, in turn, cause major crystal symmetry reduction and charge redistribution that accelerate bandgap closure and promote superconductivity relative to pure hydrostatic compression. Our findings highlight a hitherto largely unexplored mechanism for creating superconducting dense hydrogen, with implications for exploring similar phenomena in hydrogen-rich compounds and other molecular crystals.

Shear viscosity of hadronic matter at finite temperature and magnetic field

We calculate the transport coefficient of hadronic matter in the presence of temperature and magnetic field using the linear sigma model. In the relaxation time approximation, we estimate the shear viscosity over entropy density $\eta/s$. The point-like interaction rates of hadrons are evaluated through the $S$-matrix approach in the presence of a magnetic field to obtain the temperature and magnetic field-dependent relaxation time. We observe that the transport coefficients are anisotropic in the presence of the magnetic field. We calculate the temperature and magnetic field-dependent anisotropic shear viscosity coefficients by incorporating the estimated relaxation time. The value of viscosity over entropy density is lower in the presence of a magnetic field than the value of it in a thermal medium. The behavior of the perpendicular components of the shear-viscous coefficient is also discussed. We consider the temperature-dependent hadron masses from mean-field effects in this work.

A 3-D crustal shear wave velocity model and Moho map below the Semail Ophiolite, eastern Arabia

SUMMARYThe Semail Ophiolite in eastern Arabia is the largest and best-exposed slice of oceanic lithosphere on land. Detailed knowledge of the tectonic evolution of the shallow crust, in particular during and after ophiolite obduction in Late Cretaceous times is contrasted by few constraints on physical and compositional properties of the middle and lower continental crust below the obducted units. The role of inherited, pre-obduction crustal architecture remains therefore unaccounted for in our understanding of crustal evolution and the present-day geology. Based on seismological data acquired during a 27-month campaign in northern Oman, Ambient Seismic Noise Tomography and Receiver Function analysis provide for the first time a 3-D radially anisotropic shear wave velocity (VS) model and a consistent Moho map below the iconic Semail Ophiolite. The model highlights deep crustal boundaries that segment the eastern Arabian basement in two distinct units. The previously undescribed Western Jabal Akhdar Zone separates Arabian crust with typical continental properties and a thickness of ∼40–45 km in the northwest from a compositionally different terrane in the southeast that is interpreted as a terrane accreted during the Pan-African orogeny in Neoproterozoic times. East of the Ibra Zone, another deep crustal boundary, crustal thickness decreases to 30–35 km and very high lower crustal VS suggest large-scale mafic intrusions into, and possible underplating of the Arabian continental crust that occurred most likely during Permian breakup of Pangea. Mafic reworking is sharply bounded by the (upper crustal) Semail Gap Fault Zone, northwest of which no such high velocities are found in the crust. Topography of the Oman Mountains is supported by a mild crustal root and Moho depth below the highest topography, the Jabal Akhdar Dome, is ∼42 km. Radial anisotropy is robustly resolved in the upper crust and aids in discriminating dipping allochthonous units from autochthonous sedimentary rocks that are indistinguishable by isotropic VS alone. Lateral thickness variations of the ophiolite highlight the Haylayn Ophiolite Massif on the northern flank of Jabal Akhdar Dome and the Hawasina Window as the deepest reaching unit. Ophiolite thickness is ∼10 km in the southern and northern massifs, and ≤5 km elsewhere.

Study on the Anisotropic Shear Strength of Rough Joint via 3D Scanning, 3D Printing, and 3D Discrete-Element Modeling

The anisotropic shear strength of rough joints is examined from both experiments and numerical simulations in this paper. The rough joints in the experiment are prepared by combining 3D laser scanning and 3D printing technology. The direct shear tests are conducted in eight shear directions under constant normal load condition (CNL) with the normal stress of 0.2, 0.5, and 1.0 MPa. The dramatic variation of shear strength in different shear directions is observed from experimental results. Meanwhile, the numerical simulation based on the three-dimensional discrete-element method (DEM) is conducted, in which, the method to generate the identical rough joint by connecting triangular walls is proposed. With the calibrated microparameters from the unconfined compression test and direct shear test, the anisotropic shear strength is also observed in the numerical simulation, which is consistent with the experimental result. Accordingly, the topography anisotropy of the rough surface is analyzed, and the statistical parameter, Z2θ, is found closely related to the anisotropic shear strength of rough joints. Based on this, the Barton model is modified to estimate the shear strength of artificial joints with an anisotropic effect involved.