Recent research has focused on reinforcing sand consolidated through microbial -induced carbonate precipitation (MICP) with alkali -treated fibers to enhance its mechanical properties and mitigate brittleness. This research investigated how modified fiber affected the microstructure and properties of MICP solid sand. The fiber content (0, 0.5, 1, 3, and 5%), pretreatment concentration (0, 1, 5, 10, and 20%), pretreatment time (0, 0.5, 1, 2, and 4 h), and pretreatment temperature (25, 35, 45, and 55 degrees C) required for the experiment were determined by MICP testing. The interactions between fiber, sand, and calcium carbonate(CaCO3) were analyzed by calcium carbonate content(CaCO3(%)), unconfined compressive strength (UCS), environmental scanning electron microscopy (ESEM), and X-ray diffraction (XRD). The specimen without added fiber had a UCS of 2.13 MPa, the UCS of the added fiber sample was 2.8 MPa, which was 31.46% more than that of the specimen without added fiber, and the UCS of the specimen with added alkali -treated fiber was 3.62 MPa, which was 70% more than that of the specimen without added fiber and 28.57% more than that of the added untreated fiber. The optimum content of jute fibers was 0.5%, and the optimum concentration of alkali treatment of jute fibers was 10% for one hour.

Microbially induced calcium carbonate precipitation (MICP) is an emerging technology proposed for soil improvement in recent years. It has environmental protection and sustainability advantages. Reinforcing fiber can effectively improve the flexibility of MICP-treated sandy material. The MICP synergistic fiber solidified sand research results have attracted significant attention recently.This paper introduces the reaction mechanism and curing method of MICP, including injecting soaking, spraying, pre-mixing, single-phase, and step-by-step injection methods. It summarizes the effect of various fibers, including jute fiber, animal fiber, polypropylene fiber, carbon fiber, polyester fiber, and polyvinyl alcohol fiber (PVA), on the synergistic curing of sand. This research project summarized the following results: 1) The two-step injection method improves the uniformity of calcium carbonate distribution in the sample. 2) Adding fiber provided more adsorption sites for bacteria and increased nucleation sites; 3)The fibrous network structure of the sample, combined with the 'bridge' effect, is efficient in preventing cracks from expanding in soil samples.; 4) The friction and cohesion between the fiber itself and the sand column improve the overall stability of the sand sample; 5) The coupling of fiber, sand, and generated calcium carbonate improves the flexibility and tensile strength (TS) of specimens; 6) For the two factors of fiber content and fiber length, the effect of fiber content on unconfined compressive strength (UCS) is greater than fiber length. Fiber type is influenced more than fiber length. Meanwhile, the development prospect of MICP synergistic fiber was pointed out, including 1) the influence of fiber pretreatment and modification on curing effect; 2) the fiber and sand mixed, uniform distribution method; 3) The method of mixing the fibers improves the properties of the cured specimens.

The mixed culture of Trichoderma reesei and Aspergillus niger were found to improve lignocellulase production and ameliorate the composition (Fang et al., 2010; Fang et al., 2013; Zhao et al., 2018) [1-3]. However, the mechanism behind remained unclear. Here we conducted multi-omics study of the mixed culture to elucidate the mechanism comprehensively, including proteomics of the secretomes, metabolomics of the fermentation broths and transcriptomics. The mechanisms at transcriptional, proteomic and metabolomic levels were clarified. Proteomics show many proteins in the secretomes were up-regulated by the mix culture of T. reesei and A. niger, and lignocellulase production and the composition were improved, but the protein numbers and abundances of the lignocellulases were reduced. Transcriptomics demonstrate that lignocellulase gene expressions, stress responses and anti-stress were co-regulated in T. reesei, and that most lignocellulase genes in T. reesei were up-regulated and most A. niger lignocellulase genes were down-regulated. Metabolomics reveal the chemicals and the mechanism of the communication between T. reesei and A. niger in the mixed culture for improved lignocellulase production. The secondary metabolites such as p-cresol, nodularin and tolazoline could play important roles. Integrative analyses indicate that the secondary metabolites, stress-response, anti-stress, starch and sucrose metabolism and lignocellulase gene expressions were orchestrated. As a result, the roles of T. reesei and A. niger in the mixed culture were defined. The mechanism of the mixed culture for improved lignocellulase production was obtained, in short T. reesei was the major role and A. niger the minor. This work provides theory and targets as basis to obtain complete understanding of the mechanism and guide engineering of the microbial consortium of T. reesei and A. niger for further improvements.

Carbon dioxide enhanced shale gas recovery (CO2-EGR) technology is of great significance for shale gas extraction and carbon dioxide storage in subsurface, which involves the competitive adsorption in shale nanopores. Adsorption comparisons between the kerogen matrix and slit and between the pure gas and gas mixture are conducted in this study. Kerogen matrix and slit models are built with the type II-A kerogen macromolecules and adsorptions of CH4 and CO2 are modelled. It is seen: 1) The gas absolute adsorption increases with its molar fraction while decreases with temperature. The Langmuir pressure for CO2 decreases while that for CH4 increases with their molar fractions. The adsorption selectivity of CO2 over CH4 decreases with the increase in pressure and the CO2 fraction, while it is higher in the matrix than that in the slit. Water significantly reduces the gas adsorption especially for matrix. 2) CO2 has high affinity to the Sulfur and Nitrogen functional groups, while CH4 molecules mainly adsorb on the Sulfur, Nitrogen and Carbon functional groups, While water are strongly bound to the Oxygen functional groups with water cluster formed at high contents. 3) Lower interaction energies are shown in the matrix compared with the slit due to the adsorption superposition, which results in gases preferentially adsorbed in the matrix then on the slit surface in the kerogen slit model. The water interaction energy is lowest due to the hydrogen bond, while the interaction energy of CO2 is much smaller than that of CH4 indicating its adsorption advantage.

A numerical study was conducted on the damage behaviors of sandstone specimens with an embedded rough fracture under triaxial stress conditions. The discrete element method was used to study the deformation and cracking characteristics, and the effects of triaxial stress state, fracture width and inclination angle on the mechanical properties were also investigated. The results are as follows: (1) The strength of fractured rock decreased with the increase of fracture width ratio and the yield stress under conventional triaxial stress is higher than those under true triaxial tests with the same mean confinement; (2) For fractured rock models with small width ratios (0.2, 0.4 and 0.6), the strength increases as the fracture angle turning towards the principal stress direction. The shear damaged bond ratio decreased with the increase of confining pressure when σx=σy , while its ratio increased slightly with the fracture angle when σx≠σy; (3) For the large-width fractured rock model with a width ratio 1.0, the strength first decreased and then increased with the increasing inclination angle. At inclination angles of 0° and 30°, damage first occurred near fracture surface, then it propagated along the diagonal direction, and the ratios of bond damage caused by tension and shear failure were almost equal. While the shear damaged bond ratio was much higher than that by tension at inclination angles of 60° and 90°.

Evaluating unconsolidated reservoirs' internal stability concerning fine migration is essential for the commercial development of natural gas hydrate resources. In this pursuit, we use our newly developed visualized sand production cell and validated CFD-DEM model to study the fines migration dynamics in unconsolidated reservoirs. Our approach leveraged the novel Analysis Software for the Internal Stability of Granular Soils (ASISGS), equipped with three distinct criteria. Experimental observations revealed reservoirs with smaller fine particles experience intensified sand production, characterized by extended production durations and a heightened presence of fine particles in the produced sand. The fine particles move faster than the coarse ones. The ‘coarse matrix with floating fines’ is a premise for fines migration. The flow channel severely clogged by fine particles may reopen, leading to erosive bursts. Kezdi law and the Kenney and Lau criterion in ASISGS software successfully assessed reservoirs' internal stability, consistent with our experimental results. However, the Sherard criterion sometimes overestimated the reservoir's internal stability. Rather than a binary distinction, our research posits a continuum between internally stable and unstable reservoirs. From a CFD-DEM perspective, we discerned two predominant failure modes leading to sand production: erosion of fines and destabilization of the primary sand arch subsequently triggering a sand skeleton reorganization. The smaller the fine particle size, the slower the coordination number increase, the lower the coordination number the platform reach, and the more significant the fine particle migration. With the hydrodynamic drag force exerted by the fluid, fine particles move faster and farther than coarse particles. The formation process of the sand arch includes initial, migration, and equilibrium stages. Overall, this study offers valuable insights into fines migration and its impact on sand production, providing a foundation for effective sand management in natural gas hydrate reservoirs.

D-glucaric acid is a platform chemical of great importance and the consolidated bioprocessing (CBP) of lignocellulose by the microbial consortium of Trichoderma reesei C10 and Saccharomyces cerevisiae LGA-1C3S2 features prospects in biomanufacturing it. Here we compared some representative lignocelluloses in Northwest China including corn stover, wheat straw and switchgrass, and the leading pretreatments including steam explosion, subcritical water pretreatment, sodium hydroxide pretreatment, aqueous ammonia pretreatment, lime pretreatment, and diluted sulfuric acid pretreatment. It was found that sodium hydroxide pretreated switchgrass (SHPSG) was the best substrate for D-glucaric acid production, resulting in the highest D-glucaric acid titers, 11.69 ± 0.73 g/L in shake flask and 15.71 ± 0.80 g/L in 10L airlift fermenter, respectively. To the best of our knowledge, this is the highest D-glucaric acid production titer from lignocellulosic biomass. This work offers a paradigm of producing low-cost D-glucaric acid for low-carbon polyethylene 2,5-furandicarboxylate (PEF) and a reference on developing biorefinery in Northwest China.

The global issue of microplastic pollution and its migration has become a significant environmental concern for nations and international bodies such as the United Nations. Many older landfills, lacking proper protective linings, serve as major sources of microplastics. These particles not only degrade into smaller fragments but also migrate through the soil, contaminating groundwater and reaching the oceans, thereby affecting global ecosystems (Rajasekar et al., 2021). Notably, microplastics have been identified in marine species and within human cerebral thrombi, indicating their extensive reach and potential health implications (Kozlov, M., 2024). To address this, we present a novel approach utilizing urease-producing bacteria within landfill environments to induce calcium carbonate precipitation directly between microplastic particles, rather than just among soil particles. This microbial-induced calcite precipitation (MICP) aims to aggregate microplastics, reducing their mobility and preventing their infiltration into groundwater. MICP acting between soil particles can also increase soil adhesion and decrease its permeability. Furthermore, this study integrates the use of plastic-degrading bacteria to break down microplastics, tackling the issue from multiple angles. This combined microbial strategy provides a proactive solution for controlling microplastic generation at the source, potentially alleviating a significant global environmental threat. We have also outlined an experimental design for this study, which assesses the effectiveness of microbial-induced calcite precipitation (MICP) in aggregate microplastics. The process involves cultivating urease-producing bacteria and applying a cementation solution to microplastics in cylindrical molds. Introducing plastic-degrading bacteria alongside or following the MICP treatment may be considered supplementary, and potentially unnecessary, if the microplastic particles are effectively encapsulated and aggregated by MICP. The MICP-treated samples (also with plastic-degrading bacteria) are then tested for unconfined compressive strength (UCS) and subjected to simulated rainfall to evaluate the impact on soil permeability and structural integrity. The experimental outcomes will also include an analysis of eroded particles to evaluate the potential for microplastic degradation by plastic-degrading bacteria following erosion. This will help determine which area—landfill subsoil, groundwater systems, or marine environments—the microplastics are likely to reach before being degraded by these bacteria.

Mineral grains serve as the basic units of rocks. Understanding rock materials at the grain-scale level allows us to unveil the underlying fundamental mechanisms, thereby facilitating the development and innovation of engineering solutions. This is especially significant amidst the current energy and sustainability transition, where many geomechanics applications require a shift towards more scientific, environmentally friendly, and sustainable approaches. The Discrete Element Method (DEM) is a numerical tool that has been widely used to understand the micro-mechanisms associated with rock deformation and cracking. Here, through reviewing the past 50 years of research, we present a comprehensive state-of-the-art review of mechanical and coupled hydromechanical (H-M) DEM models tailored to elucidate the grain-scale behaviour of crystalline rocks. We first examine the logic, principles, and capabilities of existing DEM models and conceptual grain-based models (GBMs) and identify crucial aspects of the grain-scale behaviour of crystalline rocks. We also assess the existing coupled hydro-mechanical models and their adaptability, and then introduce a capable Hydro-GBM model specifically developed for grain-scale simulation of crystalline rocks. Finally, we discuss the selection of DEM micro parameters, which is an important and longstanding challenge for DEM, and accordingly, we provide some strategies that could alleviate the challenge. It is found that the widely used DEM parallel bonded contact model would lead to significant deficiencies in capturing the real grain-scale cracking behaviours of crystalline rocks. The previous GBM models also suffer from limitations in reproducing the grain-scale cracks and cracking modes (tension and shear cracks). Fluid-driven grain-scale cracking is at an early stage and the Hydro-GBM model appears to be an appealing tool. This review also emphases that reconsiderations of past micro-parameter selections of DEM models are necessary. In the review, we also argue that modelling of rock grain-scale H-M behaviour should be based on appropriate considerations of: (a) the solid phase (mechanical), (b) the fluid flow (hydro), and (c) micro parameters for both the mechanical and hydro aspects.

Embracing the principles of circular economy and zero-waste, this study aligns with the United Nations' twelfth sustainable development goal by investigating warm mix recycled asphalt technology as a sustainable solution for utilizing aged asphalt materials. This approach not only enhances pavement quality but also minimizes resource consumption and environmental impact. We critically examine the limitations of conventional warm mix technologies in improving the high and low-temperature performance of aged asphalt and propose innovative solutions. Our research focuses on the rheological characteristics of warm mix reclaimed asphalt, emphasizing the roles of Sasobit, Evotherm M-1, and YDWB-1 warm-mix additive in rejuvenating aged asphalt. We reveal that Sasobit and Evotherm M-1 enhance the asphalt’s elasticity, thus improving its resistance to permanent deformation, while YDWB-1 displays unique properties that can influence the asphalt's mechanical behavior in different ways. Our findings suggest optimal mixing ratios for these agents and demonstrate their varied impacts on rutting properties at high temperatures and other mechanical characteristics. The study concludes with insights into the optimal combinations of these warm-mix additives to enhance the high and low-temperature qualities of aged asphalt, marking a step forward in sustainable road construction and material science.

To thoroughly investigate the stability of reservoir rock mass in heavy oil thermal recovery projects, this study explored the dynamic mechanical properties and deformation behaviors of thermally-treated red sandstone from the oil-immersed reservoir, taking the dry and water-saturated reservoirs as the comparison. The results show that the dynamic compression strength and energy transmission rate of oil-immersed and thermally-treated red sandstone are enhanced. With the help of scanning electron microscopy (SEM) tests, we observed the grain-coating on the surface of the mineral particles of oil-immersed rock. The grain-coating enhances the rock matrix integrity and leads to the mechanical strengthening effect of oil-immersed rock. The fractal dimension of oil-immersed samples is smaller than that of dry and water-saturated samples. In addition, the theoretical values of the damage constitutive model are consistent with the experimental data, which verifies the validity of the damage model. Our new findings support that the oil weakens the deformation resistance ability of the micro-crack part but strengthens that of the rock matrix.

Fractures are widely present in subsurface formations, and fracture extension under ultralow temperature conditions is important for tasks such as liquid nitrogen fracturing and underground storage of liquid natural gas or liquid air. Therefore, the fracture toughness of sandstone under ultralow-temperature conditions was investigated using three-point bending tests of the NSCB specimens. The specimen damage processes were monitored using the DIC technique, and the changes in the pore microscopic characteristics after ultralow-temperature treatment were observed using CT and SEM. The results show that fracture toughness of dry sandstone was insensitive to the variations of the ultralow temperature (-30 to -120 degrees C), whereas that of saturated sandstone increased gradually with the decrease of temperature due to the cementing effect of ice. DIC analysis showed that the peak strain around the fracture tip increased, and the fracture extension time was shortened with a decrease in temperature for both dry and saturated sandstone samples. The minerals shrank and the samples became more compacted with a decrease in temperature for the dry samples, resulting in their brittle characteristics under ultralow temperatures. The enhanced cementation effects of ice under ultralow temperatures induced high internal stress and rapid energy release upon failure of the saturated samples. Large pores shrank owing to pore collapse and filling after the one -cycle ultralow-temperature freeze-thaw treatment.

Sand production, a challenge in the geo-energy industry, compromises reservoir integrity and equipment by eroding and transporting sand grains from unconsolidated and weakly consolidated reservoirs, which is crucial in oil, gas, geothermal, and underground hydrogen storage systems. Effective management and accurate prediction of sand behaviors are essential for maintaining wellbore stability and optimizing energy extraction processes. This study comprehensively reviews the discrete element method (DEM) used over the past three decades for simulating sand production, a significant phenomenon causing substantial equipment damage and financial losses in the geo-energy industry. Our review elaborates on the adaptation of DEM for modeling the mechanical behavior of sandstone, sandy materials, and granular packs, which is essential for predicting and mitigating sand production. We categorize the review into five key areas—force models, bond models, damping models, particle shape, and particle size distribution. These aspects are pivotal in enhancing the realism of DEM simulations. The review critically assesses current methodologies and their limitations, emphasizing the need for precise parameter selection in DEM to yield realistic simulations, aligning with the emerging trends and technological advancements in geotechnical engineering.

d-glucaric acid production from lignocellulose is a valuable research field, but meets the same challenge as other biorefinery processes that prevents it from commercialization, high production costs. The very path to tackle this is to increase the titer, rate and yield (TRY) of d-glucaric acid production and simplify the process, on which this study focused. Herein we used a novel, clean and environmentally friendly pretreatment, subcritical water pretreatment (SCWP), based on which we compared consolidated bioprocessing (CBP) by the microbial consortium composed of Trichoderma reesei C10 and Saccharomyces cerevisiae LGA-1C3S2 with separated hydrolysis and fermentation (SHF). CBP was found to be advantageous over SHF because of its comparable yield, much more simplified bioprocess and bigger space for cost reduction. Then CBP was upgraded to direct consolidated bioprocessing (dCBP) by adapting the microbial consortium in the raw liquors of SCWP containing inhibitors and toxic chemicals. As a result, more integrated biorefinery processes from corn stover (CS), wheat straw (WS), rice straw (RS) and switchgrass (SG) to d-glucaric acid under SCWP were developed and scaled up from shake flasks to 10 L fermenters, stirred and airlift. The TRYs of d-glucaric acid were improved significantly. The airlift fermenter was preferable for the dCBPs, producing the highest concentrations of d-glucaric acid, which were 10.03 g/L from subcritical water pretreated CS (SWCPCS), 9.53 g/L from SWCPWS, 8.87 g/L from SWCPRS and 10.66 g/L from SWCPSG respectively. Subsequently, the dCBPs were coupled with the downstream separation to establish a closed-circuit circulation and 30 rounds was run successfully. The highly integrated process from lignocellulose to d-glucaric acid with the smallest number of single unit operations was obtained and reported for the first time, providing an important design for biorefinery. This work is of great significance for biomanufacturing d-glucaric acid and other bio-based chemicals.

The idea in-situ resource utilization (ISRU) for building extraterrestrial bases on the moon and Mars has become increasingly popular. This review outlines the latest developments in fabrication of space construction materials using microbial induced carbonate precipitation (MICP) technology. This innovative approach uses the urease activity of Bacillus pasteurianus to promote the precipitation of calcium carbonate from external carbon and nitrogen sources. By using lunar and Martian soil as raw materials, this method presents a sustainable alternative to the difficult and costly process of transporting building materials from Earth to space. The paper delves deeply into three critical aspects: the ongoing advancements in understanding lunar and Martian soils, including the detailed composition and sourcing methods for lunar soil simulant and Martian soil simulant; the intricate workings and substantial potential of MICP technology; and the enhancements achieved in the physical properties of space bio-bricks, spotlighting the notable improvements in compressive strength which present them as promising materials for space construction. The discussion also underscores the current challenges, such as technical bottlenecks, and outlines necessary future strides in research, harboring optimism for the pivotal role of MICP technology in revolutionizing space construction through the development of robust and eco-friendly materials. The review anticipates a bright future, envisaging MICP as a cornerstone in the imminent realization of lunar and Mars bases, marking a significant stride in mankind’s space exploration journey.

Abstract Recognizing the limitations of Microbially Induced Calcite Precipitation (MICP) for sand consolidation, particularly the insufficient mechanical strength and the uneven distribution of precipitated calcite, our research takes an innovative approach. For the first time, we compare the potential of various polypeptide additives, including polylysine, polyaspartic acid, and polyglutamic acid, to enhance the MICP process. The optimal polypeptide was determined as polylysine, which could increase sand samples’ unconfined compressive strength (UCS) by 35.03% after MICP treatment. The optimal polylysine concentration is 100 mg/L, and the cementing liquid cost increased by only 3%. When the polylysine concentration exceeded 100 mg/L, the UCS of sand-solidified samples decreased. Environmental scanning electron microscope (ESEM) images showed that calcium carbonate and sand were bonded more tightly with polylysine added, and the distribution of calcium carbonate was uniform in the sand samples treated by MICP. X-ray diffractometer (XRD) showed calcium carbonate’s crystal form is calcite. This research signifies a crucial step forward in optimizing MICP for sand consolidation, potentially transforming applications in construction, geotechnical engineering, and environmental remediation.

Microbial-induced CaCO3 precipitation (MICP) is an innovative and rapidly developing technology for sand solidification. The idea for this research project was built based on the concept of sustainable development and environmental protection. The specific material used for solidification was soluble calcium ions generated by the reaction of limestone waste, a kind of calcium-rich industrial waste from a quarry, and acetic acid. Using Ca(CH3COO)2 (prepared from limestone waste) as a calcium source resulted in a 31.87% lower MICP cost compared to using CaCl2. An unconfined compressive strength (UCS) test was conducted to characterize the macroscopic mechanical properties of bio-cured sand columns. The mineral composition and the microstructure of sand columns were examined by using X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM). After response surface optimization, the optimal conditions for the reaction of limestone and CH3COOH were determined, and the calcium acetate yield was up to 96.81%. The UCS of sand samples treated with limestone/acetic acid was 10.61% higher than that of samples treated with calcium chloride. This research confirmed the feasibility of cheap limestone waste and soluble calcium ions generated by acetic acid as a calcium source, instead of calcium chloride, for solidifying sand columns in the MICP process.

Microbially induced calcite precipitation (MICP) is a promising technology for sand fixation, ground stabilisa-tion, concrete crack repairment, and contaminated soil remediation. Sporosarcina pasteurii is the most used urease-producing bacterium for MICP applications. This study proposes a novel, cost-effective culture medium for S. pasteurii using corn-steep liquor as a cheaper nitrogen source, partially replacing the soybean peptone, decreasing the medium cost by 50.5 %. The optimal fermentation conditions were determined by single-factor experiments at a temperature of 30celcius, an initial pH of 8.0, and an inoculation amount of 0.5 %. The optimal medium composition was determined by orthogonal experiments at 15 g/L soybean peptone, 30 g/L corn-steep liquor, 10 g/L urea, and 3 g/L sodium dihydrogen phosphate. As a carbon source, lactose was found to inhibit urease activity and should not be added.The novel medium increased the urease activity by 24.2 % and enhanced the unconfined compressive strength (UCS) of the MICP-treated sample to 2.39 MPa, which increased by 21.3 %. XRD analysis shows that calcite, the most stable crystal form of calcium carbonate, was formed in the samples. ESEM images show more calcium carbonate generated on the sample surface, and the cementation between sand particles was better. Therefore, this novel, cost-effective medium made the Sporosarcina pasteurii show satisfying MICP performance and alle-viated economic concerns about the large-scale application of MICP.

Rock cracking is of key concern to many geological applications. On a grain scale, rock fracturing depends on not only the external load but also the mechanical properties of the mineral grain and grain boundary. In this study, we investigated the effect of rock grain-scale mechanical param-eters on fluid-driven cracking behaviours and discussed the identification of micro mechanical parameters in the grain-based model. A coupled hydro-grain-based DEM model (Hydro-GBM) is used to reconstruct rock microstructures and simulate hydraulic fracturing. We analyzed the influences of the main micro-mechanical parameters of mineral grain and grain boundary and explored the responsible micro-mechanisms. Results including crack initiation pressure, break-down pressure, partitions of intragranular and grain boundary cracks in tension/shear are pre-sented in detail. Then, based on the parameter analysis, some issues in identifying micro parameters in existing DEM simulations are discussed. We proposed a formulation to determine contact friction angle, which could eliminate the long-standing mismatch of shear cracking be-tween experiment and simulation. We also suggested the importance of calibrating micro results in grain-based modelling. The presented study systematically revealed the effects of rock grain-scale properties on hydraulic fractures and could provide valuable references to the selection of micro mechanical parameters in future modelling.

Sand production is one of the oldest challenges in the oil and gas industry, causing billions of dollars of losses every year. The main aim of the research reported here is to use our validated 3-D numerical model (Song et al., 2020) based on computational fluid dynamics (CFD) coupled with the discrete element method (DEM) to investigate sand arching under hydrodynamic force in oil and gas production wells. The main findings are as follows:The sand arches observed in our 3-D model have complex 3-D backbones. Sand arches with fewer sand grains are more stable and more common than those with more sand grains. Sand arches contain particles that are coarser than the average size of sand in reservoirs. Most associated angles in arches are less than 180°. For a concave arch with an associated angle greater than 180°, a bead hanging from the equator can be compensated by neighboring particles. A concave sand arch exists only when static friction is introduced. The two arch abutments of sand arches bear the maximum contact force. The critical drawdown pressure gradient of the reservoir increases when the frictional coefficient between sand and screen/liner material increases from 0.0 to 0.75. However, simply increasing the frictional coefficient does not enhance the stability of sand arches if the frictional coefficient is greater than 0.75. The sand skeleton generates greater inner contact force when a higher fluid pressure gradient is introduced. If the drag force exceeds the maximum strength of the sand arch, catastrophic sand production occurs without a new sand arch forming. The collapse and reconstruction of sand arches cause the fall and rebound respectively of the mean coordination number. The greater the mass of the sand production, the greater the mean coordination number's maximum retracement. The proposed method is sufficiently robust and efficient for application to the simulation of fluid-particle interactions for a wide variety of problems in granular systems.