Understanding the energy release rules during shear damage of rock structural planes is of great importance to reveal the mechanism of slip-type rockbursts. To investigate the energy evolution characteristics during shear deformation of structural surfaces, numerical simulations of direct shear experiments on rough rock structural surfaces are carried out using particle flow code. In the simulation, acoustic emission (AE) monitoring is achieved by tracking the kinetic energy change of the two particles located in both sides of the fractured crack. Based on the spatiotemporal distribution of AE energy, the failure patterns of the structural plane and the intensity of energy release are firstly correlated. Then, the effects of normal stress and joint roughness coefficient (JRC) of structural planes on AE b-value are explored. Finally, the feasibility of taking AE b-value as a precursor of shear failure of rock structural planes is demonstrated. The results show that the gnawing break at protrusions has the most intense energy release, while the energy release related to frictional abrasion and rock block fracturing is lower. For the AE b-value during the whole deformation process, it decreases continuously with increasing normal stress. Under a given normal stress, when JRC is less than 12, the change of b-value is not significant; once JRC exceeds 12, the b-value decreases continuously with increasing JRC. For cases with more active AE activity in the pre-peak deformation stage, the b-value appears to decrease significantly after the shear deformation proceeds to the post-peak damage stage from the pre-peak stage. It indicates that the AE b-value can be employed as a precursor of shear failure of rock structural planes.

We present a 2D DEM-based model with bonded particles to simulate the uniaxial loading of a porous material. In this paper, we focus on the numerical study of the model parameters at the microscale (normal and tangential stiffnesses of the bonds, bond length, and friction coefficient) influence on the Young modulus and compressive strength of the modeled material. Young’s modulus exhibits linear dependence on the normal stiffness, whereas its dependence on the other parameters is more complex and hard to characterize. We illustrate that compressive strength depends linearly on the normal and tangential stiffness as well as on the bond length but it relates quadratically to the friction coefficient. Additionally, we illustrate that the model is scalable and that Young’s modulus and compressive strength do not depend on the particle size. The provided study allows the construction DEM-based model of porous material with prescribed properties to perform a simulation of uniaxial and triaxial loading of complex heterogeneous materials.

This study investigates the effects of particle convexity, sphericity and aspect ratio (AR) on the behaviour of sheared granular materials using two-dimensional discrete element method simulations. Isotropic, dense and loose assemblies with different particle shapes were prepared and subjected to drained shearing via biaxial compression until the critical state was reached. Macroscopic characteristics such as strength and dilatancy are presented. The factors underlying the macroscopic behaviour are then investigated by considering the coordination number, fabric anisotropy, particle moment, friction mobilisation at contacts and particle rotation. For the range of shapes considered here, the data indicate that the shear strength decreases as particle convexity and sphericity increases while the shear strength increases with increasing AR. The shear strength and convexity are weakly correlated, however a stronger correlation is observed between AR and strength. The volumetric strain at large strains tends to increase with increasing AR. There is a stronger correlation between the critical state strength and both the critical state coordination number and the critical state mechanical void ratio than there is between the critical state void ratio and the critical state strength. The contact fabric anisotropy, the magnitude of the moment transmitted by particles and the friction mobilised at the contacts are important factors underlying strength. The critical state strength increases as both the mean particle moment and the mean mobilised friction increased. Analysis of particle rotation provides insights into the response of the granular materials to shearing.

The present work suggests numerical approach to determine phase transitions in small-ion Coulomb crystals in ion traps. The proposed method is based on the analysis of the trapped Coulomb crystal geometrical parameters a cross size \(\rho _i\), relative polar angle between neighboring particles \(\Delta \phi _i\), the surface area \(S_A\) and the volume \(V_p\) of a circumscribed polyhedron of a Coulomb crystal. We demonstrate an analysis procedure for the numerical determination of extremes of interpolated geometrical parameters functions. Phase transitions points are defined as the extremes of the proposed interpolated functions.

We present a novel smoothed particle hydrodynamics-discrete element method (SPH-DEM) approach for the simulation of deformable granular media. First, we show how the method converges to the analytical solution in a simple contact mechanics problem, namely the Hertz contact law for elastic spherical grains. Second, we analyze the evolution of a 2D packing of disks under uniaxial compression, displaying the evolution of key metrics of the packing such as the coordination number and the vertical stress. We show that the code produces data in quantitative agreement with what is known from literature. Finally, we demonstrate that our SPH-DEM coupling can be used to study packings of deformable grains from the onset of jamming to extremely compacted states, reaching packing fractions of \(\phi \simeq 0.995\).

In the field of smart materials, microencapsulated self-healing technology has received a lot of attention in recent years. However, the existing microcapsule preparation techniques continue to have difficulties controlling the structural parameters of microcapsules at the microscopic scale, and there are difficulties in investigating the mechanical properties of microcapsules based on a single structural parameter experimentally. In addition, the commonly used Finite Element Method (FEM) also has significant limitations in investigating dynamic damage problems in non-homogeneous, discontinuous materials. To address the aforementioned issues, the Discrete Element Method (DEM) is used to create a numerical model of a single microcapsule. The reliability and feasibility of the discrete element model are demonstrated by utilizing the microcapsule's mechanical intrinsic model and experiments. Further, the discrete element models are employed to analyze the influence of microcapsule structure/material parameters on the crack resistance and fracturability of a single microcapsule, discuss the micromechanics of the microcapsule damage process, and predict the rupture mode and rupture location of a single microcapsule. It is shown that (1) the larger the wall thickness and smaller the diameter of the microcapsule, the stronger the deformation resistance of the microcapsule, but the rupture load and nominal rupture stress increase linearly with the increase of wall thickness and decrease nonlinearly with the increase of diameter; (2) the maximum stress field during compression of small deformation microcapsules occurs in the polar region, and the initial scattered damage appears in the polar region, also the scattered damage gradually develop into one or more main cracks along the meridian and (3) large deformation microcapsule compression through three stages of elastic deformation, plastic deformation and hardening, and gradually occur three kinds of the morphology of "spherical", "drum-shaped" and "butterfly-shaped", while rupture after producing scattered cracks and fragments in the near-polar region.

Top coal is difficult to break and then flow out of the support opening at the end area of longwall top coal caving (LTCC) panels, which is an important source of the top coal loss and seriously restricts the further improvement of the top coal recovery. The end area of LTCC panels includes the arrangement area of roadway support and transition support in this research. Taking the drawing mechanism of top coal at the end area as the main research object, theoretical models of drawing body in the advancing direction and layout direction are established based on Bergmark–roos model, respectively. Under the constraint effect of roadway and support, the drawing body has the characteristics of the bidirectional cutting and the over-development toward the advancing direction and the middle part of the panel. Furthermore, numerical simulations of top coal drawing at the end area under different caving methods were carried out by the discrete element software PFC3D. The results show that compared with the middle support drawing, the roadway support drawing and transition support drawing can increase the top coal recovery by about 6%. The asymmetry of the initial top coal boundary at the end area is significant, which can be effectively adjusted by the way of interval top coal caving technology, improving the top coal recovery. In addition, the special support and matched transportation equipment are tentatively developed, which provides the equipment foundation for top coal drawing at the end area. The research results have important theoretical and field guiding significance for further realizing the caving technology and improving the top coal recovery at the end area.

Joints commonly exist in the surrounding rock of underground roadway and have an important impact on the mechanical properties of underground roadway. In order to study the mechanical characteristics of the failure of joints on surrounding rock, the compression indoor test and the discrete element PFC2D numerical simulation study of jointed sandstone roadway with different dip angles are carried out to analyze the influence of joints on the strength characteristics of surrounding rock and the evolution of crack propagation. The results show that the peak strength of surrounding rock decreases first and then increases with the increase in joint angle around the roadway, and the peak strength curve shows a similar "V" shape. Moreover, the strength of the samples in the roadway with joints is less than the peak strength in the roadway without joints. The joints reduce the bearing capacity of the surrounding rock. The peak strength is related to the angular distribution of joints. When there is no joint in the roadway, the cracks are mainly concentrated in the direction from the left side of the roadway to the upper left corner and from the right side of the roadway to the lower right corner. When there have joints in the roadway, the displacement field of the roadway and the propagation law of the crack are basically consistent. One end of the joint extends toward the shoulder of the roadway, and the other end extends to the upper right corner. At the same time, there is an obvious vertical crack at the bottom of the roadway. The expansion, convergence and coalescence of microcracks and the formation of macroscopic failure zone are the fundamental reasons for the ultimate failure of surrounding rock.

Compliant contact force models were developed and mainly used to investigate simple impacts of two bodies. It is therefore unclear how they will perform in more complex cases, where simultaneous, multi-zone impact may occur. The aim of this study is to investigate phenomena that occur in such impacts and to study the effectiveness of preselected contact force models in their modelling. For this purpose, the study addressed collisions that occur in a collinear system of 3 to 6 particles made of steel, aluminium, and bronze. The results obtained for each force model were referenced to the FEM analysis. To compare the performance of the models, the Benchmark Velocity Indicator (BVI) is proposed. The study showed that during simultaneous, multi-zone impact direct switch from the restitution to compression phases may occur and subsequent collision along the same normal may take place. Such phenomena are not incorporated in current compliant contact force models; therefore, the study showed the need for their further improvement. The best models proposed by Kogut and Etsion (KE) and Jackson and Green (JG) achieved average errors equal to 3.89% and 4.15%, respectively. However, the same models in their worst cases reached error values of 38.66% and 33.77%. The article concludes with proposals for future improvements.

The leading investigation focuses on the current scenario of peristaltic action with gyrotactic micro-organisms and Williamson nano fluid through the arterial wall under the highlighted impacts of solar mimetic appliance and magneto-hydrodynamics effect. The animation of chemical reaction takes place with the collaboration of activation energy and solar system as encountered through Rosseland’s estimations. The Buongiorno model is applied for further analysis of Brownian diffusion and thermophoresis effects on thermal radiation, chemical reactions, and the dynamics of gyrotactic micro-organisms. In such peristaltic action, viscosity as well as conductivity is presumed to vary with temperature. The controlled DE’s (differential equations) are interpreted by taking the assumption of the lowest Reynolds number and highest wavelength, and numerical findings for such a non-dimensional set of equations were launched by employing the BVP4c technique. Through the use of pictorial interpretations, the implications of diverse physical parameters upon the flow stream, the dynamics of gyrotactic micro-organisms, thermal radiations and concentration distribution were calculated. Major findings about velocity depict that viscosity and the Williamson variable decline the velocity profile due to the resistive behavior of these forces. The magneto-hydrodynamics effect produces a Lorentz retarded force, which slows blood motion during surgical scenarios. The heating phenomenon is accelerated by the Brownian motion variable and the thermophoresis parameter. The activation energy parameter results in a low concentration distribution, whereas the Brownian motion parameter causes a higher density of motile microorganisms. The bio-convection constant and peclet number diminish the motile micro-organism density. The conductivity parameter increases the temperature profile in the pumping section while the Prandtl number slows down the heating phenomenon.

Cracks are a ubiquitous phenomenon in rock masses, and their presence can significantly impact the dynamic mechanical behavior and evolution process of rocks. In this study, we utilized a two-dimensional particle flow code (PFC2D) to investigate the dynamic compressive strength, peak strain, and dynamic elastic modulus of randomly distributed cracked sandstone samples. We analyzed the effect of varying the number of pre-existing cracks on rock deformation and energy absorption under impact loading. Our findings demonstrate that the dynamic compressive strength, peak strain, and dynamic elastic modulus of cracked sandstone follow a two-parameter negative exponential relationship, with crack density being the most influential factor on dynamic compressive strength. The duration of each stage of cracked rock deformation is dependent on the number of pre-existing cracks, with an increase in the number of cracks resulting in a shorter elastic deformation stage. The presence of cracks also affects the energy absorption rate and elastic energy storage capacity of a sample, with a higher number of prefabricated cracks resulting in greater elastic energy conversion and crushing energy dissipation capacity. The interaction of cracks weakens the dynamic elastic response of rock specimens, and this effect becomes more pronounced with increasing crack density and loading rate. Our study provides valuable insights into the influence of cracks on rock dynamic mechanical behavior and has practical implications for rock engineering design and risk assessment.

The process of applying sand particles to increase the traction between wheel and rail is reported to be less than 20% efficient. To better understand entrainment efficiency, the process is simulated using the Discrete Element Method. The simulation results are validated against full-scale experimental observations in terms of entrainment efficiency and particle velocity for ten case studies with different positioning of the sand nozzle. The numerical simulations confirm the experimental observations wherein the highest efficiency can be achieved when the sander is aimed at the wheel/rail nip. When aiming the sander at the wheel, the values of entrainment efficiency from simulations and experiments show some discrepancy which can be related to the numerical assumptions. Calculating coefficients of traction between the rail and wheel from the simulation data for the four cases of an un-sanded contact, and with the sander aimed at the rail, the nip, and the wheel (all with the same angle) show an increase in the coefficient of traction for all sanded cases compared to the un-sanded case.

This paper presents an elaborated discussion on numerically handling single and double shock problems via the implementation of a meshless method, namely the generalized interpolation material point (GIMP) method. Oxygen-free high thermal conductivity copper and aluminum materials were considered. The capability of GIMP to accurately simulate such type of shock wave propagation problem is demonstrated and discussed via the 2-D plane strain solid mechanics formulation. GIMP is a modified material point method (MPM) that has been developed as an excellent numerical tool to solve dynamic problems involving large deformation, penetration, and fragmentation. However, double-flyer impact problem has rarely been simulated by using such a meshless method tool. In this work, the development and implementation of a set of well-tuned parameters are presented for modeling and analysis of both single and double shock experiments. Several procedures, including the discretization effect, were first performed within the GIMP framework to simulate single-flyer impact. Along with a modified update-strain-last method and an elastoplastic Johnson–Cook strength constitutive model, it is observed that the numerical results could be hugely improved when such a full mass matrix noise control strategy was utilized with optimized parameters for the numerical noise control. Thus, large oscillations that occur at the contact interface during high-speed impact can be smeared out without losing significant wave propagation features. Mie–Grüneisen equation of state was introduced to accurately identify the pressure-related shock-induced properties. Artificial defined explicit crack was introduced to model the spall and recompact in double-flyer impact. The simulation results of double-flyer impact problems, including free surface velocity, internal stress, and shock wave propagation presented via spatial–temporal diagrams, were shown to be in good agreement with previously reported data from experiments, finite element method, and analytical calculations.

Improving the accuracy and convergence rate of the smoothed particle hydrodynamics (SPH) method is still one of the challenges that researchers are trying to achieve. In this research, the first- and second-order convergence schemes have been used for the first and second spatial derivatives, respectively, in continuity and linear momentum conservation equations to increase accuracy and convergence rate. These schemes have been implemented in the open-source code of DualSPHysics, one of the prominent and powerful software of the SPH to calculate the particle velocity and pressure of the Taylor–Green vorticity benchmark problem. Both the standard and the improved solvers were evaluated with the same numerical settings, different particle spacing, and Reynolds numbers of 100 and 1000 with the same dimensionless time. Up to three orders of magnitude improvement in the accuracy were achieved in the results of the improved solver, as well as a significant increase in convergence rate.

Tensile strength is one of the important mechanical parameters for controlling the development of cracks in the Loess Plateau. However, the tensile strength of soil is difficult to be precisely measured due to the lack of satisfying laboratory techniques. Unconfined penetration test (UPT) is commonly used as an indicator to predict soil tensile strength characteristics, while there has been less research study about test parameter values range of UPT and micromechanical characteristics at failure. This study finished 50 groups of UPTs of remolded loess with different disk diameters (12.36–27.81 mm) at various sample heights (37–87 mm) based on Q2 loess in Lintong areas, and the crack development and failure essence in the different failure modes process were investigated by the discrete element modeling. The results showed that disk diameters and sample height were closely correlated with the failure mode. The failure of remolded loess in the UPT is not only tensile failure, which also can occur compression failure and tensile–compression coupling failure. Among them, when the ratio of disk diameters to sample height is about in the range of 0.189–0.309, the sample appears tensile failure. In addition, the ratio of compressive and tensile crack numbers in the sample is 0.16–0.22 in the tensile failure mode. The numerical simulation method provides a way for the observation of failure process and crack development, thereby improving the understanding of failure essence in UPT. The findings will provide a reference way to improve test theory and method of loess tensile strength.

The impact of traverse speed on the microstructure, mechanical properties, and wear resistance of Al–16Si alloy friction-surfaced on AA1050 alloy was evaluated using smoothed-particle hydrodynamics (SPH) simulation and experimental techniques. Results revealed a 54% and 20% decrease in the height and width of the coating, respectively, as traverse speed increased from 75 to 115 mm/min. Moreover, a corresponding increase in the unbonded zone at the interface was observed. Simulation results showed the maximum shear stress at the coating/substrate interface for samples coated at traverse speeds of 75, 95, and 115 mm/min to be 83, 95, and 112 MPa, respectively. As traverse speed escalated from 75 to 115 mm/min, the predicted torque and vertical force required for friction surfacing increased by 92% and 22%, respectively. The surface roughness declined while interface roughness increased by 49% and 86%, respectively, upon raising the traverse speed from 75 to 115 mm/min. An increase in the traverse speed from 75 to 95 mm/min resulted in a 11% grain size reduction and 13%, 12%, and 8% increases in hardness, strength, and wear resistance, respectively, when compared to the AA1050 substrate.

Rainfall and high leachate levels are the most prominent causes of MSW dumpsite instability. The multiphase mass flow originating from the failure of dumpsites often results in severe societal and environmental impacts. Numerical analysis and scenario simulation of the dumpsites from initiation to propagation is essential for strategizing risk mitigation. This study develops a two-phase Random SPH (RSPH) approach for modelling the large deformation MSW mass flows, incorporating spatial variability of material properties and pore-fluid pressure using the random field theory. The variability of MSW properties is characterized for uncertainty modelling based on the analysis of 584 laboratory tests on MSW from 28 countries. The proposed approach is applied for the risk assessment of three operational dumpsites, namely (i) Ghazipur dumpsite, Delhi, India, (ii) Koshe dumpsite, Addis Ababa, Ethiopia, and (iii) Hulene dumpsite, Maputo, Mozambique. Investigation of the uncontrolled and controlled surface infiltration scenarios indicated that providing a cover system over the waste dump is an effective risk minimization technique with a reduction of over 30% in the runout distance and over 40% in the maximum kinetic energy of the mass flow. Further, deterministic analysis with homogenous material properties is found to underestimate the vulnerability to failure, highlighting the significance of probabilistic approaches in identifying the high-risk zones around a dump site.

Estimating the shear mechanical parameters of field-scale joints using laboratory tested results is a challenging task due to the scale effect. To further understand the effect of specimen size on shear mechanical parameters, this study not only focuses on the joint length effect, but also explores the effect of specimen height (the dimension in the direction perpendicular to the joint surface), while the latter has not been paid enough attention in the existing studies. Based on the particle discrete element method, numerical direct shear experiments are carried out for multiple specimen height and joint length conditions. The effects of specimen height and joint length on the pre-peak, peak and post-peak shear deformation stages are analyzed in detail. The results suggest that specimen height also has an effect on the shear mechanical parameters of the joints. In the pre-peak deformation stage, the specimen height effect on shear stiffness is diametrically opposed to that of joint length, while the effect on shear strength is similar to that of joint length. In the post-peak crack evolution stage, the specimen height effect also differs from the joint length effect. In terms of significance, the effects of specimen height and joint length on the same shear mechanical parameter are almost at the same level. Therefore, future experimental studies may need to pay more attention to the specimen height effect.

An electro-osmotic particulate flow is presented in this article. Fluid-particle interaction is simulated in bulged out cavity at the center. Casson non-Newtonian fluid model serves as the base liquid, while spherical & homogenous metallic particles are used to form a granular suspension. Particulate flow is modeled by using Navier–Stokes equations which assist to trace the motion of the particles, as well. The electric potential within this volume is governed by “The Poisson equation”. Moreover, the local charge density may be related to the electric potential through the “Boltzmann distribution”. In addition to this, lubrication effects are applied to take care of the skin friction of the walls. The main objective of this study is to highlight the application of electro-osmosis, such as biophysics, geomechanics, medicine, microchips, and oil and gas production. Since, electro-osmotic flow arises from the formation of an electrical double layer at solid–liquid interface. Therefore, this is a significant phenomenon in chemical separation techniques; in particular, to expedite the fluid flow in oil rigs and clay-rich soils in petroleum industries. The application of electricity stimulates the fluid to flow out of the pores of the soil, due to the ions with a positive charge.

A scalable matrix solver was developed for the moving particle hydrodynamics for incompressible flows (MPH-I) method. Since the MPH-I method can calculate both incompressible and highly viscous flows while ensuring stability through physical consistency, a wide range of industrial applications is expected. However, in its implicit calculation, both the pressure and velocity must be solved simultaneously via a linear equation with a nondefinite symmetric coefficient matrix. In this study, this nondefinite linear system was converted into a symmetric positive definite (SPD) system where only the velocity is unknown. This conversion enabled us to solve the system with well-known solvers such as the conjugated gradient (CG) and conjugated residual (CR) methods. For scalability, bucket-based multigrid preconditioned CG and CR solvers were developed for the SPD system. To handle multidimensionality during preconditioning, an extended Jacobi smoother that is even applicable in a nondiagonally dominant matrix system was proposed. The numerical efficiency was confirmed via a simple high-viscosity incompressible dam break calculation, and the scalability within the presented case was confirmed. In addition, the performance under shared memory parallel computations was studied.