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The mechanism of liquefaction and the factors that cause liquefaction behavior have previously been examined and evaluated, both analytically and experimentally; construction including liquefaction countermeasures is being implemented, based on these findings. This study presents a theoretical visualization of the mechanism of liquefaction generation and evaluates the behavior of particles in the ground. Specifically, an MPSM-DEM coupled CAE system (CAES) is employed to view the events beneath the ground, modeled three-dimensionally when an external acceleration is applied to simulate seismic waves and reveals the behavior below the surface. The numerical simulation of the liquefaction phenomenon, as represented by an MPSM-DEM coupled CAES system, clearly showed the mechanism of liquefaction generation and contributed to the design and accountability of more economical and sustainable liquefaction countermeasures, regardless of the field of specialization.

The feeding shoe, which is a critical component that connects the rotary valve to the conveying pipeline, significantly influences the performance of powder conveying systems. The Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) was employed to investigate particle dynamics within various feeding shoe designs under gas–solid two-phase flow conditions. Through comparative analyses of two-phase flow characteristics and particle trajectories, three feeding shoe configurations, namely, through, horn, and funnel types, were evaluated, along with the effects of varying gas velocities. Key structural parameters, including opening diameter and inclination angle, were systematically examined to assess their effect on particle transport efficiency. Results demonstrated that feeding shoes with a low inclination angle or a small opening diameter exhibited poor particle flow, while those with a large opening diameter tended to induce backflow on the left side. By contrast, through-type feeding shoes with a large inclination angle and equal opening diameter achieved optimal conveying performance, minimizing backflow and enhancing flow efficiency. These findings provide theoretical insights for optimizing feeding shoe designs, improving conveying efficiency, and reducing production costs, offering valuable guidance for advancements in powder conveying technology and fluid mechanics.

Optimization of complex fracture networks improves the fracturing effects and enhances production in multistage hydrofracturing technology. To understand the controlling mechanisms of multistage hydrofracturing in unconventional tight reservoirs, some governing issues, such as hydro-mechanical coupling, stress shadow effects, propagation interaction behaviours of three-dimensional (3D) multiple fractures, and 3D multistage hydrofracturing, should be addressed. However, the characterization of perforation cluster spaces and fracturing scenarios of horizontal wells, which significantly affect the evolution of the stress field and 3D morphology of the fracture network, is a challenge. In this study, to overcome the drawbacks of the traditional finite-element method in simulating 3D fracture propagation, the adaptive finite element–discrete element method is used. This method uses a local remeshing and coarsening strategy to ensure the accuracy of solutions, reliability of the fracture propagation path, and computational efficiency. The study proposes 3D engineering-scale numerical models, considering the crucial hydro-mechanical coupling and fracturing fluid leak-off, to simulate 3D multistage hydrofracturing and fracture interaction behaviours. The numerical results show that the stress shadow effects and fracture interaction behaviours become more intense once the spaces between different propagating fractures become thinner due to superposition and reduction effects in fracturing-induced shear stress variation areas. The alternate fracturing can reduce the stress shadow effects through adjusting the sequence of perforation clusters that are activated and injected with fracturing fluid. When the perforation cluster spaces become narrow, the alternate fracturing scenario can yield more fracturing fracture areas and improve the fracturing effects as compared to sequential and simultaneous fracturing.

PurposeThe purpose of this study is to simulate the tensile and shear types of fractures using the mixed fracture criteria considering the energy evolution based on the dual bilinear cohesive zone model and investigate the dynamic propagation of tensile and shear fractures induced by an impact load in rock. The propagation of tension and shear at different scales induced by the impact load is also an important aspect of this study.Design/methodology/approachIn this study, based on the well-developed dual bilinear cohesive zone model and combined finite element-discrete element method, the dynamic propagation of tensile and shear fractures induced by the impact load in rock is investigated. Some key technologies, such as the governing partial differential equations, fracture criteria, numerical discretisation and detection and separation, are introduced to form the global algorithm and procedure. By comparing with the tensile and shear fractures induced by the impact load in rock disc in typical experiments, the effectiveness and reliability of the proposed method are well verified.FindingsThe dynamic propagation of tensile and shear fractures in the laboratory- and engineering-scale rock disc and rock strata are derived. The influence of mesh sensitivity, impact load velocities and load positions are investigated. The larger load velocities may induce larger fracture width and entire failure. When the impact load is applied near the left support constraint boundary, concentrated shear fractures appear around the loading region, as well as induced shear fracture band, which may induce local instability. The proposed method shows good applicability in studying the propagation of tensile and shear fractures under impact loads.Originality/valueThe proposed method can identify fracture propagation via the stress and energy evolution of rock masses under the impact load, which has potential to be extended into the investigation of the mixed fractures and disturbance of in-situ stresses during dynamic strata mining in deep energy development.

Purpose Optimized three-dimensional (3D) fracture networks are crucial for multistage hydrofracturing. To better understand the mechanisms controlling potential disasters as well as to predict them in 3D multistage hydrofracturing, some governing factors, such as fluid injection-induced stratal movement, compression between multiple hydraulic fractures, fracturing fluid flow, fracturing-induced microseismic damaged and contact slip events, must be properly simulated via numerical models. This study aims to analyze the stratal movement and microseismic behaviours induced by multistage propagation of 3D multiple hydraulic fractures. Design/methodology/approach Adaptive finite element–discrete element method was used to overcome the limitations of conventional finite element methods in simulating 3D fracture propagation. This new approach uses a local remeshing and coarsening strategy to ensure the accuracy of solutions, reliability of fracture propagation path and computational efficiency. Engineering-scale numerical models were proposed that account for the hydro-mechanical coupling and fracturing fluid leak-off, to simulate multistage propagation of 3D multiple hydraulic fractures, by which the evolution of the displacement, porosity and fracture fields, as well as the fracturing-induced microseismic events were computed. Findings Stratal movement and compression between 3D multiple hydraulic fractures intensify with increasing proximity to the propagating fractures. When the perforation cluster spaces are very narrow, alternate fracturing can improve fracturing effects over those achieved via sequential or simultaneous fracturing. Furthermore, the number and magnitude of microseismic events are directly proportional to the stratal movement and compression induced by multistage propagation of fracturing fracture networks. Originality/value Microseismic events induced by multistage propagation of 3D multiple hydraulic fractures and perforation cluster spaces and fracturing scenarios that impact the deformation and compression among fractures in porous rock matrices are well predicted and analyzed.

This study aims to systematically analyze the effects of various operational parameters on the continuous mixing process of concrete using the Discrete Element Method (DEM) combined with a wet mixing model, with the objective of optimizing mixing uniformity and material flow to improve concrete mixing quality and efficiency in practical engineering applications. The results indicate that an appropriate water addition rate (e.g., 10 m/s) and a moderate moisture content (e.g., 2:9) can significantly enhance the uniformity of concrete mixing. Additionally, a moderate rotational speed (e.g., 200 rpm) achieved good mixing effects in a short time, avoiding issues such as oversaturation and uneven mixing. This study provides theoretical support and a data foundation for optimizing concrete mixing processes, contributing to improvements in mixing quality and efficiency in engineering practice.

As a promising and convenient numerical calculation approach, the discrete element method (DEM) has been increasingly adopted in the research of agricultural machinery. DEM is capable of monitoring and recording the dynamic and mechanical behavior of agricultural materials in the operational process of agricultural machinery, from both a macro-perspective and micro-perspective; which has been a tremendous help for the design and optimization of agricultural machines and their components. This paper reviewed the application research status of DEM in two aspects: First is the DEM model establishment of common agricultural materials such as soil, crop seed, and straw, etc. The other is the simulation of typical operational processes of agricultural machines or their components, such as rotary tillage, subsoiling, soil compaction, furrow opening, seed and fertilizer metering, crop harvesting, and so on. Finally, we evaluate the development prospects of the application of research on the DEM in agricultural machinery, and look forward to promoting its application in the field of the optimization and design of agricultural machinery.

In the past, the number of CPU cores/threads was usually less than 8/16; now, the maximum number is 128/256. As a CPU-based parallel method, OpenMP has an increasing advantage with the increase in CPU cores and threads. A parallel combined finite-discrete element method (FDEM) for modeling underground excavation and rock reinforcement using OpenMP is implemented. Its computational performance is validated in the two advanced CPUs: AMD Ryzen Threadripper PRO 5995WX (64/128 cores/threads); and 2 × AMD EPYC 7T83 (128/256 cores/threads). Then, its ability in simulating tunnel excavation under rockbolt-shotcrete-grouting support is implemented using the novel solid bolt model, which can explicitly capture the interaction between bolt, grout, and rock. The parallel performance validation of the uniaxial compression test shows: (i) for the speedup ratio, the OpenMP-based parallel FDEM obtains maximum speedup ratios of 30 (33 k elements) and 41 (3304 k elements) on the Threadripper, and 31 and 43 on the 2 × EPYC, respectively; (ii) for the scalability of speedup ratio, when the number of threads used is less than 128, the speedup ratio is always increasing with the increase of the number of threads; (iii) for the stability of speedup ratio, it has a stable speedup ratio, regardless of whether the rock is pre- or post-fractured.HighlightsA parallel FDEM for modeling underground excavation and rock reinforcement using OpenMP is implemented.Its computational efficiency is validated in the two advanced CPUs: AMD Ryzen Threadripper PRO 5995WX; and 2 × AMD EPYC 7T83 (128/256 cores/threads).Its ability in simulating rockbolt-shotcrete-grouting support is implemented using the novel solid bolt model.It obtains maximum speedup ratios of 30 (33 k elements) and 41 (3304 k elements) on the Threadripper, and 31 and 43 on the 2 × EPYC.It has good scalability and stability of speedup ratio, regardless of whether the rock is pre- or post-fractured.

The particle discrete element method (PDEM) is widely used to simulate rock and soil materials to obtain stress and strain. However, there are three shortcomings: (1) Single sphere or ellipsoids directly replace the soil particles; (2) it treats the diameters of spheres or ellipsoids as the soil particle size; (3) the overlapping particle volume is not deducted in calculating the porosity. Hence, it is difficult for the simulation of the geological body to agree with reality. This research found a rotation calculation model and a pixel counting method to make joint soil particles more accurately simulate geological materials to solve the three shortcomings. The model successfully obtained the gradation curve and porosity of the simulated geological body with joint particles. This research will further enrich and broaden the application prospects of PDEM and provide a reference for scientific research and engineering fields in geological engineering, geotechnical engineering, and petroleum engineering.

Hydraulic fracturing (HF) is one of the most effective stimulation techniques to enhance reservoir permeability. The efficiency of an HF fluid injection depends on the pre-existing discontinuities or sources of heterogeneities and these features need to be considered in a HF operation treatment. Moreover, deep reservoirs are usually located in hot dry rocks (HDR). Hence, thermal conduction through the rock and fluid and advection and convective heat transfer in the fluid can affect the fluid–rock interaction. This study focuses on HF development in deep reservoirs under a high-temperature field. Two separate scenarios are considered: a reservoir containing discrete fracture networks (DFN) and another considering blocks in a matrix as conglomerate reservoirs (there is no relation between the scenarios considered). The study discusses each reservoir separately and simulates their thermo-hydro-mechanical (THM) behaviour using the combined finite-discrete element method (FDEM). First, the capabilities of the FDEM are verified against the existing analytical solutions, and then the FDEM is employed to model HF development. The effects of controlling factors, including flow rate, fluid kinematic viscosity and DFN aperture for jointed reservoirs and flow rate, fluid kinematic viscosity and block strength in conglomerate ones, are studied. The results show that the high fracture density DFNs strongly affect the HF propagation pattern and fluid pressure rise. Moreover, the DFN’s aperture significantly alters the HF treatment behaviour. The controlling factors are observed to influence the HF pattern strongly, and a successful HF treatment requires careful consideration of all the factors. In the conglomerate reservoirs, the strength of the blocks strongly dominates the HF mechanism, in which soft blocks break and allow for uniform fluid pressure distribution and longer HFs, while hard blocks stop fluid from flowing over longer distances accumulating high fluid pressure around the injection. This mechanism excessively breaks the matrix and reduces HF efficiency. Crack branching frequently occurs in conglomerate reservoirs due to thermal exchange between the blocks, matrix, and fluid.HighlightsCoupled THM FDEM is utilized to study hydraulic fracturing in HDR.Reservoirs containing blocks in matrix or DFN are considered.The effects of controlling factors are evaluated.Recommendations to improve the efficiency of a fluid injection are suggested.