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The Weihe Basin is one of the regions with the highest concentrations of ground fissure development and the most serious disasters in China. Hidden ground fissures are formed in the shallow soil layer due to preexisting fissures generated by tectonism, hidden ground fissures suddenly exposed to the surface after heavy rainfall. Because the details of the water erosion process cannot be replicated by geological survey methods, the erosion and extension mechanism has not fully developed and the discontinuous medium numerical simulation method is well suited for simulating large deformations and facilitates a microscopic perspective in elucidating the underlying causal mechanisms. This paper deploys the discrete element method (DEM)–computational fluid dynamics (CFD) fluid–solid coupled method modeling the growth process of hidden fissures containing different soil types (sand and clay) under heavy rainfall, revealing a mechanism for the development of hidden fissures into surface fissures. The findings include: (1) the emergence process of hidden fissures into surface fissures under heavy rainfall can be summarized into four stages: subsurface erosion into hidden holes, traction into arches, collapse into sinkholes, and horizontal extension; (2) the emergence process of clay is slower than that of sand due to the constraint of cohesion; (3) the shape of the bottom seepage point affects the fissure emergence process, which is an important factor in the macroscopic performance of the exposed surface fissures. The intuitive and reproducible DEM-CFD coupled modeling used in this paper possesses important reference value for the study and prevention of water erosion ground fissures. [ABSTRACT FROM AUTHOR]

To apply the discrete element method (DEM) to simulate the interaction process between soda saline–alkali soil and subsoiling component in Northeast China, establishing the soda saline–alkali soil particle model and selecting more accurate simulation parameters are important. In this paper, we studied the soda saline–alkali soil of the Songnen Plain in China. First, we studied the geometric shape of soda saline–alkali soil particles and proposed a modeling method for single soil particles based on the multisphere combination method. Considering the cohesion of soda saline–alkali soil particles, the Hertz–Mindlin with JKR (JKR) model was used as the contact model between soil particles. Then, the calibration method was used to obtain simulation parameters of soils that are difficult to obtain experimentally. We conducted soil angle of repose (AoR) tests, the Plackett–Burman (PB) tests, and steepest ascent (SA) tests in turn to perform a sensitivity analysis for microscopic contact parameters and select the parameters that have a significant effect on the response value (static AoR), i.e., soil surface energy, soil–soil static friction coefficient, and soil–soil rolling friction coefficient. Then, the optimal combination of simulation parameters was obtained via the Box–Behnken (BB) tests, using ANOVA to optimize the multiple regression equation. Finally, the optimal parameter combination was verified by the AoR test and the direct shear (DS) test. The results showed that the parameters had good adaptability for the AoR test. However, the simulation results of the DS test were significantly different from the experimental values. Therefore, the contact model needs to be further modified by adding Bonding bonds between soil particles based on the JKR model and further correcting for Rayleigh time step, shear modulus, and surface energy. By comparing the simulation and the experimental results, it was found that the simulation results obtained from both the DS test and AoR test had relatively small errors relative to physical tests, the two trends are the same, and the values are similar. This verified the feasibility and effectiveness of the soda saline–alkali soil particle modeling method and parameter selection proposed in this paper. [ABSTRACT FROM AUTHOR]

Siliceous minerals of the Dengying Formation in the Gaoshiti–Moxi area in the central Sichuan Basin exhibit four types of quartz crystals (cryptocrystalline quartz, chalcedony, microcrystalline quartz, and megacrystalline quartz) and three structural types: cryptocrystalline, microcrystalline, and mosaic (laminated mosaic, window-hole interrupted mosaic, and arc-laminated mosaic). Siliceous minerals have a great influence on the storage performance of the reservoirs in the Dengying Formation. According to the petrophysical parameters of the Dengying Formation and porosity intersection diagrams, the siliceous dolomite and the reservoirs have low impedance characteristics, which makes it difficult to distinguish between them and leads to difficulties in the characterization and prediction of the reservoirs. The transverse wave velocity is favorable for reservoir characterization. Currently, the main method used to estimate the transverse wave velocity is petrophysical modeling, which establishes a relationship between the elastic and physical parameters of the reservoir. In this paper, the siliceous minerals in the dolomite in the study area are regarded as solid inclusions, and the calculation method of the rock matrix modulus is improved by using solid replacement. Then, an improved petrophysical model is constructed by combining the KT (Kuster–Toksöz) model, the DEM (Discrete Element Method) model, the Gassmann equation, and the Wood equation. The transverse wave velocity is estimated using the improved model under the constraint of the longitudinal wave velocity. The shapes of the transverse wave velocity curves obtained by the improved model and the deviations from the measured velocities are significantly better than those of the Xu–Payne model and other models. The results show that the improved model can effectively estimate the transverse wave velocity of the reservoir in this area, which provides a basis for future reservoir predictions in this area. [ABSTRACT FROM AUTHOR]

Featured Application: This paper provides a simulation method for extreme precipitation events in geotechnical slopes (spatio-temporal connections, forecasting, generation, impact analysis, and vulnerability and risk assessment). Our improved methods provide a valuable tool for engineering disaster early warning and contribute to a better understanding of hydrodynamic processes in general. Coal gangue is one of the largest solid wastes in the world. In previous studies, the influence and mechanisms of rainfall infiltration on coal gangue slope stability and possible rain erosion have been studied through theoretical analysis, numerical simulation, and modelling, and the results have indicated that discontinuous discrete element methods are the most suitable for determining the erosion mechanism of coal gangue slopes. In this study, we take a Guizhou coal gangue slope as a general case, use three-dimensional Particle Flow Code (PFC3D) as the key method, and combine discrete element fluid–structure coupling technology with optimized erosion shear failure theory to determine the erosion failure mechanism of coal gangue slopes. We investigate a coal gangue slope near the electric power plant in Panzhou City, Guizhou Province (China) as a case study, and conduct a comprehensive analysis of the erosion induced by the corrosion damage mechanism. We use the PFC3D method, combined with optimized rain erosion shear failure theory, for our investigation. The applied methods mainly consider dynamic inversion of the erosion process, as well as the changes in coordination number, porosity, unbalanced force, and energy dissipation. The scour damage type of the studied gully is intermittent fragmentary damage, with the following inferred damage sequence: Center–bottom–top of the slope. The entire erosion damage process can be divided into three stages: catchment–fracture, erosion–accumulation, and piping–penetration failure. In the first stage of erosion, the force chain fracture is the most severe. The maximum kinetic energy reaches 25 MJ and the coordination number decreases from 5.3 to 4.0, whereas the porosity increases from 0.42 to 0.45. Unexpected lateral erosion and expansion occur at 40–60 m (in the central slope) in the y-direction of the slope, the unbalanced force reaches 7500 N, and the peak porosity is increased by 10%. This paper provides a simulation method for extreme precipitation events in geotechnical slopes (contributing to spatio-temporal connections, forecasting, generation, impact analysis, and vulnerability and risk assessment). Our improved methods provide valuable tools for engineering disaster early warning, and contribute to a better understanding of hydrodynamic processes in general. [ABSTRACT FROM AUTHOR]

China is the largest vegetable producer in the world, and vegetable production is more geographically concentrated in the Huang-Huai-Hai region and the Yangtze River Basin. There are significant challenges ahead for increasing the average yields of the vegetables in this region. The effects of a cultivation system, a mulched ridge with a double row (MRDR), were evaluated by using the 2ZBX-2A vegetable transplanter newly designed in this paper. The key parameters of the equipment were designed and optimized by using the human–computer interaction method and the discrete element method according to agronomy requirements. Compared with the traditional ridge (TR) system on two typical solanaceous vegetables (eggplant and capsicum), the uniformities of the plant spacing and the planting depth in the MRDR system were significantly improved. Finally, the fresh fruit yield in the MRDR system increased significantly (p < 0.05) by 40.8% and 35.3% compared with that in the TR system for eggplant and capsicum, respectively. In addition, the water use efficiency (WUE) was also 54.9~59.7% higher under the MRDR system than under the TR system. All the results indicate that the MRDR system has the potential to improve the yields and WUE of solanaceous vegetables in the Huang-Huai-Hai Plain of China. [ABSTRACT FROM AUTHOR]

The talus-like rock mass is a special kind of geomaterial widely distributed in southwestern China, which has induced serious engineering disasters for tunneling engineering. However, the mechanical behavior of the talus-like rock mass remains unclear as the previous studies mainly focused on similar geomaterials such as the soil–rock mixtures. In this paper, we have carried out both experimental and discrete element method (DEM)-based numerical analyses to investigate the shearing characteristics of the talus-like rock mass collected from a real project site. Large-scale direct shear tests reveal that the strength parameters increase with the block content, which is different from the traditional soil–rock mixture. A dependence has been discovered in that the specimen dilation becomes more obvious under lower normal stress and larger block content. It is also observed that higher normal stress is beneficial for crushing blocks. The force chains obtained in the DEM simulations show that distinct internal structures are generated in the rock samples with different block contents. The distribution of coordination number establishes the dependence of fabric stability on block content during shearing. Bond-break evolution reveals the tendencies of crushed particles were consistent with those of experimental tests. The findings provide a more in-depth understanding about the mechanical behavior of the talus-like rock mass, which helps to uncover the cause of the collapse of the real tunnel project. [ABSTRACT FROM AUTHOR]

Liquid-fertilizer deep-application techniques are techniques for applying fertilizers to the root system of crops, which can effectively improve the utilization rate of fertilizers and reduce application amounts. Due to the soil viscosity of soils in the cold region of Northeast China, the soil return rate of furrow openers for liquid-fertilizer deep applications is low, which can easily cause excessive volatilizations of liquid fertilizers. Therefore, aiming at the operational requirements of low soil disturbance for liquid-fertilizer furrowing and deep applications, an efficient soil-returning liquid-fertilizer deep-application furrow opener was innovatively designed based on soil characteristics during the inter-cultivation period in the cold region of Northeast China. The discrete element method (DEM) was used to analyze the operating performance of the high-efficiency soil-returning liquid-fertilizer deep-application furrow openers, which is determined by key operating parameters including width and slip cutting angle. The DEM Virtual Simulation Experiment results show that the optimal combination is the width of 37.52 mm and a slip cutting angle of 43.27°, and the test results show that the optimal performance of the high-efficiency soil-returning liquid-fertilizer deep-application furrow opener is that the soil disturbance rate is 51.81%, and the soil-returning depth is 52.1 mm. This paper clarifies the relationship between the width and the slip cutting angle in furrowing resistance and soil disturbance and the mechanism by which the width and slip cutting angle affect soil disturbance. Above all, this study provides a theoretical and practical reference for the design of liquid-fertilizer deep-application furrow openers. [ABSTRACT FROM AUTHOR]

Steel slag (SS) is industrial waste, and there is a large amount of SS to be treated in China. Its disposal generates severe environmental pollution. One of the best ways to use SS is as a road base material. This paper reviews the possibility of using SS in semi-rigid base and evaluates the performance of SS base course. The interaction between three stabilizers (cement, lime–fly ash, and cement–fly ash) and SS is analyzed, and the influence of modifier content on the performance of base course is evaluated. The potential laws between SS, curing time, and unconfined compressive strength, as well as drying shrinkage and temperature shrinkage, are discussed and their effects on the performance of the base course are revealed. The finite element method, discrete element method, and molecular dynamics can be used to analyze the freeze-thaw, rutting resistance, and crack development of SS base. In addition, compared with traditional macadam base, the CO2 emissions for the use of SS base are slightly more, one of the disadvantages of its use in production, transportation, and compaction. However, considering the overall mechanical, economic, and environmental benefits, it is recommended to use SS in semi-rigid base course. The future research scope of SS as base material is suggested. [ABSTRACT FROM AUTHOR]

Compared with the commonest geosynthetics-reinforced soil structures, layered geogrids–sand–clay reinforced (LGSCR) structures (School of Architecture and Civil Engineering, Shenyang University of Technology, Shenyang 110870, China) can replace granular materials with clay as the primary backfill material. Up until now, the performance of LGSCR structures under triaxial compression has been unclear. In this paper, the discrete element method was used to simulate the triaxial compression test on the LGSCR samples. Based on the particle flow software PFC3D, three types of cluster particle-simulated sand and the reinforced joints of the geogrid were constructed by secondary development. The effects of the geogrid embedment in sand layers, the number and thickness of sand layers in relation to the deviatoric stress, and the axial strain and the shear strength index of the LGSCR samples were analyzed. The results showed that laying the sand layers in the samples can improve their post-peak strain-softening characteristics and increase their peak strengths under a high confining pressure. A geogrid embedment in sand layers can further enhance the ductility and peak strength of the samples, and in terms of the shear strength index, there is a 41.6% to 54.8% increase in the apparent cohesion of the samples. [ABSTRACT FROM AUTHOR]

The high energy consumption and low crushing length qualification rate of traditional straw returning machines in the main maize-growing regions of northeast China make it difficult to promote straw returning operations in the region. The primnoa locust mouthpart is extremely efficient in cutting maize rootstocks. In this paper, it was found that there are significant differences between the primnoa locust mouthpart and the conventional machine, these exist mainly in the cutting edge structure and cutting motion. Thus, this paper develops a coupled bionic design for structural and kinematic coupling elements to develop a bionic straw returning machine. This paper found that the operating performance of the bionic straw returning machine was mainly affected by the blade rotation radius and the output rotation speed of the drive mechanism through DEM (discrete element method) simulation, and the optimal combination of the two parameters was 248 mm rotation radius and 930 r/min output rotation speed. Finally, this paper finds that the most obvious operational performance difference of the bionic straw returning machine compared with the traditional straw returning machine is that it can reduce the cutting power consumption by 9.4–11.7% and improve the crushing length qualification rate by 10.4–14.7% through the operational performance comparison test. Based on the above findings, this paper suggests that in future research and development of straw returning machines, more attention can be focused on finding suitable bionic prototypes and improving bionic design methods. [ABSTRACT FROM AUTHOR]

Featured Application: This paper aims to reduce the rate of broken and uncleared grain during the corn threshing process. In terms of structural design, a new corn threshing cylinder based on the longitudinal axial flow threshing method and three different types of T-type rasp bar, separating straight rod, and spiral extracting rod were devised. In terms of research technology, discrete element method solution (DEM) software was used to analyze the threshing process of corn ears. In terms of experimental design, the effective combination of structural parameters was obtained by the three-factor multiple test. These works can be used in the structural design and parameter setting of threshing mechanisms of corn combine harvesters. Corn harvesting mode has gradually changed from ear harvesting to direct grain harvesting. In view of the problems of high moisture content in corn harvesting in China, such as the rates of broken grains (BGR) and uncleared grains (UGR) being too high, a new single longitudinal axial threshing cylinder was designed, which mainly included a cylinder spindle, a spiral feeding inlet, a T-type rasp bar, a separating straight rod, and a spiral extracting rod. Firstly, the three states of grain during the threshing process and the key influence factors of threshing and force analysis of corn ears in the threshing device were analyzed, then the structure of the threshing cylinder was designed, and its parameters were determined by theoretical analysis results. The arrangement mode of threshing elements adopted a combination of a T-type rasp bar, a separating straight rod, and a spiral extracting rod with a 6-head spiral pattern and an arrangement step of 250 mm. Secondly, the arrangement step of threshing elements was determined by discrete element method solution (DEM) simulation; the result showed that the average movement velocity was 55.04 m/s and the threshing time was 6–8 s. Finally, a multiple factors experiment of the threshing device was carried out, and the result showed that the order of the effect factors of the BGR and UGR was cylinder rotational speed > concave clearance > feed amount. When cylinder rotational speed was 309.17 r/min, concave clearance was 35.48 mm, and the feed amount was 6.13 kg/s. The verification experiment result showed that the BGR and UGR were 1.24% and 1.33%, respectively, which meet standard requirements. The research results could provide a reference for the design of a high moisture content grain threshing device and combine harvester. [ABSTRACT FROM AUTHOR]

This study is part of the preliminary research for the Chang'e 7 project in China. The Chang'e 7 project plans to drill to penetrate the lunar polar soil and collect lunar soil samples using a spiral groove structure. Ice in the cold environment of the lunar polar region is one of the important targets for sampling. In the vacuum environment of the lunar surface, icy soil samples are sensitive to ambient temperature and prone to solid–gas phase change as the temperature increases. To predict the temperature range of lunar soil samples, this study analyzed the effect of thermal parameters on the temperature rise of lunar soil particles and the drill using discrete element simulation. The parameters included in the thermal effect analysis included the thermal conductivity and specific heat capacity of the drilling tools and lunar soil particles. The simulation showed that the temperature of the icy lunar soil sample in the spiral groove ranged from −127.89 to −160.16 °C within the thermal parameter settings. The magnitude of the value was negatively correlated with the thermal conductivity and specific heat capacity of the lunar soil particles, and it was positively correlated with those of the drilling tools. The temperature variation in the drill bit ranged from −51.21 to −132 °C. The magnitude of the value was positively correlated with the thermal conductivity and specific heat capacity of the lunar soil particles and the thermal conductivity of the drilling tool. [ABSTRACT FROM AUTHOR]

Most of the discovered high-temperature geothermal energy systems are often related with granite that is characterized by natural faults, fractures and cracks of different size. However, the porosity and permeability of the granite matrix is very low, greatly limiting the efficiency of heat extraction in granitic rock. Chemical stimulation, which is regarded as one of the most important means of reservoir stimulation, has consequently received more and more attention. In this paper, a Triassic granite obtained from the eastern region of Liaoning Province in China was reacted with three different concentration of mud acid solution (8% HCl + 1% HF, 10% HCl + 2% HF, 12% HCl + 3% HF) and the resulting microstructure changes studied by scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR). The experimental results show that the number of micropores in the granite increases after chemical corrosion by mud acid solution. A higher mud acid solution concentration results in a much higher pore volume. Triaxial compression tests on the granite before and after chemical corrosion were carried out to study the effect of acidification on the mechanical characteristics of granite, showing that the peak stress and elastic modulus of granite decreases 25.7% and 16.5%, respectively, after exposure to mud acid solution (12% HCl + 3% HF) corrosion for three weeks at room temperature. The particle flow program PFC2D based on discrete element method was used to investigate the mechanical response before and after the chemical corrosion. Considering that the granite is rich in microcracks, the study is simplified by considering them all grouped into one main closed fracture. The influences of main crack inclination angle, crack length, friction coefficient and confining pressure on the mechanical response were investigated. Under the triaxial compression loading state, wing cracks appear at the initial crack tip, then secondary cracks begin to appear. The sensitivity analysis shows that three characteristic strengths (crack initiation strength, damage strength and peak strength) are strongly correlated with crack length, crack inclination angle, crack surface friction coefficient and confining pressure. These three characteristic strengths decrease 60%, 59% and 53%, respectively, compared with their initial values with the increase of main crack length from 6 mm to 22 mm, while they present positive correlation with the fracture friction coefficient from 0 to 1.0 and confining pressure from 10 to 50 MPa. There is a critical inclination angle of the main crack (i.e., 45°), meaning that these three characteristic strengths of granite decrease with inclination angles smaller than 45°, while they increase with an inclination angle larger than 45°. After the corrosion effect of mud acid solution on granite, the pore structure was changed and mechanical properties was damaged, which further affect the failure mode and failure process of granite samples affected by mud acid solutions. This paper provides a theoretical reference for evaluating the effect of chemical stimulation technology on the mechanical characteristics of granite, serving for the continuous hydraulic stimulation design after the chemical stimulation. [ABSTRACT FROM AUTHOR]

Blast furnace slag, a by-product of the iron and steel production process, contains a significant amount of untapped heat resources. Currently, China is entering a period of rapid growth in scrap production, making efficient scrap utilization a new research focus. One approach to improving scrap utilization is preheating. This study proposes a new method of preheating scrap using high-temperature slag in a drum. The discrete element method is employed for numerical simulation, which involves constructing a three-dimensional model. The study explores three influencing factors: the mass ratio of high-temperature slag to scrap, the shape of the scrap, and the drum rotational speed. The main objective is to investigate the heat transfer situation between the high-temperature slag and the scrap. The results indicate that the optimal heat transfer effect in the drum is achieved when the mass ratio of high-temperature slag to scrap is 2:1, the scrap is spherical in shape, and the drum rotational speed is 12 rpm. [ABSTRACT FROM AUTHOR]

The parameters of the discrete element simulation model for rice field soils serve as valuable data references for investigating the dynamic characteristics of the walking wheel of high-speed precision seeding machinery in paddy fields. The research specifically targets clay loam soil from a paddy field in South China. Calibration of essential soil parameters was achieved using EDEM_2022 software (and subsequent versions) discrete element simulation software, employing the Edinburgh Elasto-Plastic Adhesion (EEPA) nonlinear elastic-plastic contact model. The tillage layer and plough sub-base layer underwent calibration through slump and uniaxial compression tests, respectively. Influential contact parameters affecting slump and axial pressure were identified through a Plackett–Burman test. The optimal contact parameter combinations for the discrete element model of the tillage layer and plough sub-base layer were determined via a quadratic rotational orthogonal test. The accuracy of the discrete element simulation model's parameters for paddy field soils was further validated through a comparative analysis of the simulation test's cone penetration and the field soil trench test. Results indicate that the Coefficient of Restitution, surface energy, Contact Plasticity Ratio, and Tensile Exp significantly influence slump (p < 0.05). Additionally, the Coefficient of Restitution, Contact Plasticity Ratio, coefficient of rolling friction, and Tangential Stiff Multiplier significantly impact axial pressure (p < 0.05). Optimal contact parameters for the plough layer were achieved with a particle recovery coefficient of 0.49, a surface energy of 18.52 J/m2, a plastic deformation ratio of 0.45, and a tensile strength of 3.74. For the plough subsoil layer, optimal contact parameters were a particle recovery coefficient of 0.47, a coefficient of interparticle kinetic friction of 0.32, a plastic deformation ratio of 0.49, and a tangential stiffness factor of 0.31. Results from the cone penetration test reveal no significant disparity in compactness between the actual experiment and the simulation test. The calibrated discrete element model's contact parameters have been verified as accurate and reliable. The findings of this study offer valuable data references for understanding the dynamic characteristics of the walking wheel of the entire machinery in high-speed precision seeding in paddy fields. [ABSTRACT FROM AUTHOR]

The utilization of sediment voids for natural gas storage represents the future direction of salt cavern underground gas storage (UGS) in China. In this study, we first analyzed the way in which the sediment interacts with the salt caverns and the equilibrium state of the process. Subsequently, a novel approach employing the Discrete Element Method (DEM) for simulating sediment-filled salt cavern UGS was introduced, successfully modeling the operational process of sediment-filled salt cavern UGS. Moreover, deformation, plastic zone behavior, effective volume shrinkage rate, equivalent strain, and safety factor were employed to assess the impact of sediment on salt cavern stability. The findings indicate a positive influence of sediment on salt cavern stability, particularly in regions directly contacting the sediment. Deformation and effective volume shrinkage of the cavern were effectively mitigated, significantly improving the stress state of rock salt. This effect is more pronounced at lower internal gas pressures. In summary, sediment enhances the stability of salt caverns, providing a long-term and stable environment for natural gas storage within sediment voids. [ABSTRACT FROM AUTHOR]

This study attempts to optimize the arc-shaped coned disk affecting the uniformity of the earlier designed fertilizer apparatus (FA), in particular, for application in the rice–oil rotation region in the middle and lower reaches of the Yangtze River, China. Based on theoretical analysis, a circular coned disk with the curvature gradual decline (GD) from top to bottom was designed, and the equation of the circular cone was determined. The EDEM discrete element software was used, using the coefficient of variation of the fertilization amount consistency in every row, the coefficient of variation of the fertilization amount stability, and the coefficient of variation of the fertilization amount consistency in the same row as evaluation indices. Simulations and comparative tests of FA performance were performed for three cases of the busbar top-to-bottom curvature variation: (i) gradual increase (GI), (ii) gradual decline (GD), and (iii) zero (0) variation. The experimental results show that at the FA rotation speed of 100~120 r/min and tilt of 1°~5°, the optimized FA had the optimal performance. High tilts and low rotation speeds provided the worst performance, with the variation coefficient of inter-row fertilization amount consistency of the FA below 10.23%. The variation coefficient of fertilizing amount stability was lower than 6.74%. The variation coefficient of intra-row fertilizing amount consistency was lower than 3.52%, while all performance indicators met the quality requirements of fertilizer discharge. Bench tests of the FA revealed that the variation coefficient of inter-row fertilizing amount consistency of the FA was below 10.23%, the variation coefficient of fertilizing amount stability was below 6.74%, and the variation coefficient of intra-row fertilizing amount consistency was below 3.52%. Field tests of the FA revealed that the variation coefficient of inter-row fertilizing amount consistency was below 7.68%, the variation coefficient of fertilizing amount stability was below 4.95%, and the variation coefficient of intra-row fertilizing amount stability was below 3.57%. All parameters were better than the industry standard, demonstrating that the FA had good fertilizing performance and met the quality requirements of field fertilization operations. [ABSTRACT FROM AUTHOR]

Underground mining activity in the karst mountain in southwestern China has induced several large-scale rocky landslides and has caused serious casualties. At present, there is a lack of systematic research on the formation mechanism of landslides in this area using multi-method fusion technology. First, the orthophoto images of the landslide area obtained by UAV photography were used to analyze the deformation characteristics of the landslide. Second, the failure characteristics of the strata overlying the goaf were analyzed by geophysical detection. Finally, the deformation response characteristics of the mountain under underground mining were analyzed by UDEC numerical simulation. The results revealed that during the underground mining, the failure process of the mountain occurred in four stages: fracture expansion, subsidence and collapse, shear sliding, and multi-level sliding. Gently dipping soft–hard alternant strata and a blocky rock mass structure formed the geological foundation of the landslides. Underground mining accelerated the fracturing of the overlying strata and the formation of a stepped penetrating sliding surface. Tensile movement of the structural planes of hard sandstone in the free face, and shear sliding of the weak mudstone layer, were the main causes of the landslides. The slope instability mode was tension-shear fracturing, shear sliding, back toppling, and compressive shear failure. In addition, the fracture propagation in the overlying strata and damaged geological structure revealed by the geophysical detection were consistent with the simulation results. This study provides ideas for the precise countermeasures of disaster prevention and mitigation for similar landslides in this area. [ABSTRACT FROM AUTHOR]

Ice-rich permafrost in the Qinghai–Tibet Plateau (QTP), China, is becoming susceptible to thermokarst landforms, and the most dramatic among these terrain-altering landforms is retrogressive thaw slump (RTS). Concurrently, RTS development can in turn affect the eco-environment, and especially soil erosion and carbon emission, during their evolution. However, there are still a lack of quantitative methods and comprehensive studies on the deformation and volumetric change in RTS. The purpose of this study is to quantitatively assess the RTS evolution through a novel and feasible simulation framework of the GPU-based discrete element method (DEM) coupled with the finite difference method (FDM). Additionally, the simulation results were calibrated using the time series observation results from September 2021 to August 2022, using the combined methods of terrestrial laser scanning (TLS) and unmanned aerial vehicle (UAV). The results reveal that, over this time, thaw slump mobilized a total volume of 1335 m3 and approximately 1050 m3 moved to a displaced area. Additionally, the estimated soil erosion was about 211 m3. Meanwhile, the corresponding maximum ground subsidence and headwall retrogression were 1.9 m and 3.2 m, respectively. We also found that the amount of mass wasting in RTS development is highly related to the ground ice content. When the volumetric ice content exceeds 10%, there will be obvious mass wasting in the thaw slump development area. Furthermore, this work proposed that the coupled DEM-FDM method and field survey method of TLS-UAV can provide an effective pathway to simulate thaw-induced slope failure problems and complement the research limitations of small-scale RTSs using remote sensing methods. The results are meaningful for assessing the eco-environmental impacts on the QTP. [ABSTRACT FROM AUTHOR]

The rockfall process is characterized by bounces of a block on the ground. The coefficient of restitution (COR), which indicates the degree of rockfall energy dissipation, has a significant effect on the rockfall trajectory. The 3-dimensional Distinct Element Code (3DEC) is an effective tool to study the rockfall trajectory, and the damping can reflect the COR in numerical modeling. However, the relationship between damping and COR is not understood. A field test is numerically modelled to investigate the correspondence between damping and COR. A series of damping–COR correspondences are obtained and compared with the field test and its previous numerical simulation to verify the rationality of the correspondences. Then, the damping–COR correspondence is adopted in a typical rockslide in Yunnan province, China. The numerical results show that the proposed method is in good agreement with practical engineering. This study provides a new method for predicting rockfall trajectory. [ABSTRACT FROM AUTHOR]

Soil organic cover technology is an effective way to solve agricultural productivity and agro-environmental issues. However, some factors limit the widespread adoption of its application, including unclear soil organic cover effects and the lack of high-performance soil organic cover machinery. Aiming to solve the existing problems, improve soil organic cover quality, and reduce energy consumption, this article reviewed the common and commercial machines by reviewing the existing literature and company products. The current problems and technical difficulties of the machines were expounded. Simultaneously, the method of design and optimization of the device (chopper, spreader, rotary tiller, and plow) and its key parts (blades, discs, and plows) were reviewed. Furthermore, the features and differences of the devices and their key parts were compared, and their advantages and disadvantages were analyzed. In conclusion, the future directions for soil organic cover technology and machinery development were suggested, including clarifying the soil organic cover effect, selecting the suitable soil organic cover patterns, and developing soil organic cover machinery. [ABSTRACT FROM AUTHOR]

Slab track structures become deformed under the effects of differential subgrade settlement. According to the properties of the China Railway Track System (CRTS) II slab track on a subgrade, a three-dimensional (3D) coupled model based on both the discrete element method (DEM) and finite difference method (FDM) was developed. The slab track and subgrade were simulated using the FDM and DEM, respectively. The coupled model was verified. The deformation of the slab track and contact forces of gravel grains in the surface layer of the subgrade were studied under differential subgrade settlement. The effects of settlement wavelength, settlement amplitude, and other types of settlements were also discussed. The results demonstrate that the settlement amplitude and settlement wavelength of the subgrade have significant effects on track deformation. The deformation amplitude of the slab track increases nonlinearly with an increasing settlement amplitude of the subgrade. Increases in the settlement wavelength and amplitude of the subgrade significantly increase the maximum value of the contact force of the gravel grains in the subgrade. The maximum contact force of gravel grains near the boundaries of the settlement section can reach two to three times that of the unsettled condition, which makes it easy to accelerate the plastic settlement of the subgrade. [ABSTRACT FROM AUTHOR]

Massive deformation often occurs when deep coalmine roadways pass through a fault zone due to the poor integrity of rock mass and high tectonic stress. To study deformation characteristics of the surrounding rock in the fault zone of a coalmine, a roadway passing through the FD1041 fault zone in China's Gugui coalfield was investigated in this research. The geo-stress characteristics of this fault zone were analyzed based on the Mohr failure theory. Furthermore, a three-dimensional model for the experimental roadway in the FD1041 fault zone was built and calculated by a numerical program based on the distinct element method. Stability conditions of the roadway, using several types of support methods, were calculated and compared. Calculation results indicated that pre-grouting provides favorable conditions for the stability of a roadway in a fault zone. Finally, an optimized support strategy was proposed and implemented in the experimental roadway. Monitored results demonstrated that the optimized support strategy is appropriate for this fault zone. [ABSTRACT FROM AUTHOR]