The initial viscosity and stability of anode slurry are important for the manufacturing process and later the lithium-ion battery’s performance. The impact of the physical properties of graphite feed material on the anode slurry’s initial viscosity and stability is fundamentally unclarified. In this study, it is discovered that the initial viscosity of an anode slurry is positively associated with non-polar part of its Gibbs surface free energy and linear independence between them is established after slurry’s viscosity test of commercial graphite with different particle size and specific surface area. It is also discovered that the anode slurry’s stability is affected by the relative size of a polar and non-polar part of Gibbs surface free energy. The slurry reveals the best stability and good specific capacity retention after >120 h rest time when polar Gibbs surface free energy is close to the non-polar part. Interestingly, there is no direct linear relationship between Gibbs surface free energy and defect of graphite particles characterized using XRD and Raman spectra. This study guides how to select graphite raw materials in the industrial production of lithium-ion batteries.
Due to the high toxicity of cyanide, researchers are trying to find an environmentally friendly and sustainable leaching process for precious metals. Thiosulfate is considered one of the most promising alternative leaching systems. Nevertheless, a traditional thiosulfate leaching solution generally consists of copper sulfate and ammonia, in which copper sulfate acts as oxidant and ammonia acts as copper ion stabilizer. However, ammonia is another toxic reagent. For this reason, a novel and eco-friendly system of copper sulfate-tartrate-thiosulfate was investigated for silver sulfide leaching in this work. The effects of rotation speed, temperature, initial pH, copper sulfate, tartrate and thiosulfate concentrations and different atmospheres on the dissolution rate of Ag2S were examined. The process of silver sulfide dissolution is controlled by chemical reactions with an apparent activation energy of 43.49 kJ/mol. The reaction orders of silver sulfide leaching with respect to copper sulfate, tartrate, and thiosulfate concentrations in copper sulfate-tartrate-thiosulfate solutions are 0.491, 1.366, and 0.916, respectively. A detailed dissolution route of Ag2S was proposed based on XRD analysis of intermediate products such as Ag3CuS2, AgCuS and (Ag, Cu)2S. XPS analysis indicated that elemental sulfur was determined to be the final oxidant product of sulfur ions from Ag2S.
Pure ZnO and Mn-doped ZnO thin films were deposited by chemical bath deposition met for various Mn doping concentrations. The structural, morphological and optical properties of the prepared films were studied using various techniques. XRD analysis shows hexagonal structured ZnO for all films and peak shift is noticed for Mn-doped films. The crystallite size is found to be increased for Mn doping. The surface morphology of the Mn-doped film shows irregular shape particles that are agglomerated. The transmittance spectra show higher transmittance in the visible region and it decreased for Mn doping, which indicates an increase in optical absorption. The band gap of Mn-doped films is found to be decreasing with Mn doping. The Mn-doped films show higher optical and electrical conductivity in UV region.
In the aluminium electrolytes, the structure and stability of different complex ions directly determine the properties of the melts, and further affect the process and technical-economic indicator for aluminum electrolysis. Herein, we investigate the effect of alkali cations on structure and stability of aluminum-oxygen-fluorine complex ions ([Al2OF6]2− and [Al2O2F4]2−) using structural characteristics, charge population analysis, Raman spectrum, cationic binding free energy, density of state based on density functional theory calculation. The research indicates the [Al2OF6]2− ion is more stable than [Al2O2F4]2− ion for isolated Al-O-F ions. When adding the alkali cations, the cations with larger sizes enhance the stability of [Al2OF6]2− and [Al2O2F4]2− ions, implying the Al-O-F ions are easier to form and exist in cryolite electrolytes with a sequence of K3AlF6>Na3AlF6>Li3AlF6. We can observe intuitively the part of electrons of Al atoms and cation disappear and then gather around O and F atoms from electron density difference diagrams. The calculated Raman frequencies of the Al-O-F ions are greatly consistent with the published literature value.
Arsenic-alkali residue is a solid waste produced by the antimony smelting industry, which can pose a threat to the environment and human health. The common wet treatment process of arsenic-alkali residue has a low recovery of valuable elements, incomplete separation of arsenic and alkali, and also produces arsenic-alkali mixed salt, which cannot realize the completely harmless treatment of arsenic-alkali residue. In order to solve these problems, the oxidative water leaching process was used to treat arsenic-alkali residue, which realized the separation of arsenic and antimony. The leaching efficiencies of arsenic and antimony were 91.79% and 0.62%, respectively. The leaching residue could be returned to the antimony smelting system to recover antimony. Then the arsenic and alkali were directly separated from the arsenic-alkali mixed salt by carbothermal reduction, and 98.3% of arsenic was removed, and the non-toxic metallic arsenic with 99.9% purity was prepared. The alkali could be recovered from the slag after reduction, which solved the problem of harmless and recycling treatment of arsenic-alkali mixed salts. The mechanism of arsenic reduction pathway was studied through thermodynamic, phase, and arsenic valence state analyses.
The adiabatic temperature is an accepted thermodynamic criterion for the occurrence of the magnesiothermic self-propagation synthesis (SHS) reaction, but the actual experimental situation is often more complicated. In this paper, the influence of kinetic factors was investigated in the SHS process by varying the experimental conditions of Mg powder particle size and sample pressure. The results show that even if the experimental raw materials were the same, the different physical states of the raw materials could lead to completely different reaction endpoints. It was found that the reaction could not be initiated when the particle size of Mg powder was larger than 96 µm. The finer magnesium powder and higher sample pressure would accelerate the reaction and reduce by-products, but also increase the evaporation and dissipation of the raw material. The results show that the size of magnesium powder near 58 µm and the sample pressure of 30 MPa were suitable experimental conditions.
The role of chloride ion in the performance of extreme thermophiles bacterium Sulfolobus acidocalarius in bioleaching process of copper sulfide concentrate at Midouk Shahr-e-Babak Complex was investigated. The gradual adaptation of bacteria to chloride ions at pH=1.5 showed that the presence of chloride ions in solution reduced the reproduction and growth rate of bacteria but did not prevent their growth. Results indicated that the effect of decreasing pH from 2.0 to 1.5 on bioleaching of copper sulfide concentrate is to increase the recovery of copper in the first few days, and nearly 100% of copper was extracted after 9 d. As the solid content in solution increases from 1% to 3%, about more 6 d was required to extract copper. Bioleaching of copper sulfide concentrate revealed that the dissolution of copper sulfide concentrates at constant pH=1.5, 1% solid content, and concentration of 0.5 mol/L and 1.0 mol/L NaCl after 9 d, was 98% and 80%, respectively; and after 21 d, it reached nearly 100% and 90%, respectively. Under the same conditions without microorganisms, copper extraction reached 62%. The kinetics of bioleaching and leaching is a combination of diffusion and chemical reaction.
The present work aims to study the microstructure and texture evolutions of thermomechanically processed 310S austenitic stainless steel. The material was cryo-rolled at 20%, 50% and 90% thickness reduction, followed by annealing at 1023, 1223 and 1323 K for 5, 15 and 30 min, respectively. After a 20% thickness reduction, strain-induced α′-martensite was seen along with deformation twinning within the austenite grains. The volume fraction of the deformation twinning was higher than that of α′-martensite. By increasing deformation from 50% to 90%, the volume fraction of α′-martensite went from 11% to 69%, and twinning was replaced by martensite. Brass, Goss, and S components were the dominant textures in the austenite phase after deformation, while the main texture components in α′-martensite were R-Cu, R-cube, F, and E. Brass component was further increased by increasing the thickness reduction in contrast to the Goss component. During annealing, martensite to austenite reversion and recrystallization occurred in the deformed austenite, which resulted in an increase in the volume fractions of the Goss and Brass recrystallization components. However, the annealing texture of the alloy was found to be approximately the same as the cryo-rolling texture. The kinetics of martensite reversion at 1223 K for 5 min was much faster than that at 1023 K. An equiaxed microstructure was not detected at 1023 K for 5 min due to incomplete martensite reversion and primary recrystallization. The optimum annealing temperature for obtaining an ultrafine grain structure was 1023 K for 15 min. Recrystallization and tangible grain growth swiftly occurred at 1173 K and 1273 K.
Improving the combustion efficiency of solid fuels is important for reducing carbon monoxide emissions in the iron ore sintering process. In this paper, the surface steam spraying technology is introduced in the sintering process based on the auxiliary combustion effect of steam on coke, and its potential to reduce carbon monoxide emissions is demonstrated. Thermogravimetric analysis experiments of coke breeze in air and air-steam mixed atmosphere are carried out, and the results show that the introduction of steam can reduce the concentration of carbon monoxide in the exhaust gas from 183×10−6 to 78×10−6. At the same time, the mechanisms of carbon monoxide emission reduction by surface steam spraying technology are analyzed from the thermodynamic and kinetic perspectives. Then, a series of laboratory-scale sintering pot tests are carried out under no spraying operation, interval spraying operation, and continuous spraying operation. The results indicate that both interval and continuous spraying operations can reduce carbon monoxide emissions. The optimal mode of steam spraying under the present experimental conditions is continuously spraying for 13 min at a volume rate of 0.053 m3/min. Compared with no spraying, the average carbon monoxide concentration in the exhaust gas is reduced from 7565×10−6 to 6231×10−6, and total carbon monoxide emissions for per ton sinter are reduced from 13.46 m3/t to 9.51 m3/t.
In this study, curdlan was used as an efficient and eco-friendly calcite depressant for flotation of fluorite/calcite. Firstly, the structure and molecular weight of curdlan were characterized. Floatation test results showed that the flotation difference between fluorite and calcite was expanded by curdlan, thus enabling the flotation separation of fluorite/calcite. The selective depression mechanism of calcite by curdlan was investigated. It was found that curdlan was adsorbed by chemical bonding of its hydroxyl group with Ca on the calcite surface, having much greater adsorption capacity for calcite than fluorite, thus selectively depressing calcite. This selective adsorption resulted in the hydrophilic modification of calcite by curdlan in flotation and hindered the hydrophobic modification caused by the subsequent adsorption of sodium oleate. However, sodium oleate could still be adsorbed on its surface due to the weak adsorption of fluorite and curdlan, resulting in hydrophobicity. Therefore, fluorite could be separated from calcite by flotation with curdlan.
Acid mine drainage (AMD) released from copper sulfide contains a large quantity of sulfuric acid and heavy metals, thus being a threat to the surrounding ecosystem. In this study, AMD is used to evaluate options for activation of chalcopyrite depressed by a high alkali solution (HAS). The results showed the flotation recovery of chalcopyrite inhibited by HAS could be increased by ∼12% with a volume ratio of AMD to HAS of 3:1. AMD promoted desorption of calcium components on chalcopyrite surfaces, and the adsorption of copper ions increased Cu-active sites on the mineral surfaces. Eventually, the copper atomic concentration of chalcopyrite surface increased by 2.2%, and the Ca—O/OH content decreased by 33.24%. Meanwhile, the area ratios of monosulfide (S2−) and disulfide (S22−) increased by 14.67% and 23.96%. Adsorption and localized electrochemical impedance spectroscopy (LEIS) confirmed that the average impedance of chalcopyrite surface obviously decreased from about 1.30×105 Ω to 1.13×105 Ω, and the adsorption amount of sodium isoamylxanthates (SIX) on the chalcopyrite sample increased by 1.99 mg/g. AMD promotes the adsorption of SIX and improves the hydrophobicity of chalcopyrite significantly. This study provided an innovative option for the comprehensive utilization of AMD, as well as the recovery of chalcopyrite from copper sulfide tailings.
Oolitic hematite possesses the characteristics of large resource reserves, low iron grade, fine embedded particle size and complex mineral composition, which is difficult to be used efficiently through traditional beneficiation process. In this work, a new technology of microwave fluidization pretreatment (MFP) was proposed to strengthen the separation of oolitic hematite. Scanning electron microscope, vibrating sample magnetometer and laser particle size analyzer were used to explore the influence of MFP on roasting magnetic separation and leaching. The results presented that compared with conventional electric furnace pretreatment, the magnetism of roasting products has been significantly improved. The iron grade was increased from 56.88% to 58.72% and recovery was increased from 88.89% to 89.32% for magnetic separation concentrate. Phosphorus content of leaching residue was reduced from 0.17% to 0.11%, and phosphorus leaching rate was increased from 83.06% to 89.77% by MFP. MFP could strengthen microcrack formation and growth, increasing the specific surface area and the grindability of ore.
The analysis upon Falkner-Skan flows under the assumption of boundary layer has attracted more interests due to their widespread applications in the industrial fields and in many engineering processes, such as percolation, thermal pad, heat exchangers, oil bed retrieval, and geothermal analysis. Therefore, this article focuses on the Falkner-Skan hydromagnetic wedge flow of graphene oxide-water nanofluid. The analysis is adopted near the stagnation point. Velocity and thermal slip phenomena are examined in the stretchable wall. Viscous dissipation and ohmic heating impacts are employed in the exploration of heat transport. The problem is computed analytically via homotopy method. The results are illustrated by velocity and heat transport mechanism against relevant parameters. Impacts of Nusselt number and skin friction are mathematically elaborated. The results report that temperature grows by increasing Brinkman number. Further thermal jump decreases the temperature field. Increasing the rates of Hartmann number improves the thickness of thermal field, while increasing Hartmann number contracts the thickness of momentum profile. This research has considerable implications in medical treatment, devices of relatively high-temperature, heat exchangers, mechanical structures, etc.
In this numerical analysis, the significance of features of squeezed viscous fluid flow in the presence of inclined magnetic field effect has been scrutinized. For the efficient heat transfer phenomenon, the viscous dissipation and Joule heating effects have also been incorporated in the temperature equation. The dimensionless conservation equations are tackled with the help of shooting method. The behavior of particular parameters contemplated in the model on the fluid motion, energy distribution rate of heat transfer and surface drag coefficient are presented graphically and discussed in detail. Significant importance of the inclined magnetic field effect is noticed in the fluid velocity and heat transfer rate. From the performed simulations, it is noticed that as Prandtl number is increased from 1 to 5, the rate of heat transfer is increased by 56%, whereas when the inclined magnetic parameter γ is increased from π/8 to π/2, the rate of heat transfer is declined by 9.7%. It is also observed that the rate of heat transfer diminishs as the squeezing parameter is hiked whereas stretching parameter of lower plate has an opposite trend.
The present study performed parametric investigation and characterizations on 17-4 PH stainless steel built by selective laser melting. Cubical samples were deposited by considering process parameters (laser power and scan speed) and scan strategy (design parameter) to investigate relative density and microhardness. Relative density and micro hardness were the maximum for samples with medium energy density and when hexagonal inside-out scan strategy was used. They were the minimum for the sample with low energy density and when strip alternate scan strategy was used. Austenite, ferrite, and small molten pools were observed on the side surface of samples from optical and scanning electron microstructure analysis. From energy dispersive spectroscopy analysis, a variation of chemical composition was observed among the samples, resulting in variation in relative density and microhardness. Austenite phase and ferrite peak at the highest intensity were also observed by X-ray diffraction for medium energy density sample. Electron backscattered diffraction results showed an increase in austenite phase with increased energy density, resulting in a microhardness change. Residual stresses induced were more for low energy density samples compared to medium energy density samples. A higher corrosion resistance (<0.5 mm/a) and an absence of corrosion cracks were present for all samples with different energy densities.
In the research on rolling bearing misalignment, the influence of bearing misalignment on the vibration characteristics of the rotor system is rarely considered, especially for the dynamic bearing misalignment. Based on the limitations of the existing research, a five-degree of freedom (5-DOF) nonlinear force model considering bearing misalignment is proposed firstly. The model comprehensively considers the parallel and angular misalignment, static and dynamic misalignment, inner ring and outer ring misalignment. Secondly, the effects of misalignment on the dynamic contact characteristics of bearing and the vibration characteristics of the rotor system are analyzed. Then, based on the dynamic response, the evaluation indexes of bearing misalignment are given. Finally, the similarities and differences between parallel and angular misalignment, static and dynamic misalignment are compared. The results show that the bearing misalignment increases the resonance speed of the rotor, and the amplitude jumping phenomenon appears in the resonance region, showing the characteristics of hardening-type nonlinearity. In terms of frequency characteristics, dynamic parallel misalignment and dynamic angular misalignment increase the amplitude of frequency components fr and 2fr, respectively. The research can be used as a theoretical basis and valuable reference for fault identification of the rotor-bearing system.
The development of high-precision and interpretable automatic waveform classification algorithms with strong adaptability is becoming increasingly significant under the background of the big data era of microseismicity. Considering the deficiency of the existing network in waveform recognition and classification, an improved model which is suitable for microseismic (MS) monitoring waveform recognition was proposed in this study based on the LeNet framework. The improved model was applied to investigate thirteen kinds of MS monitoring signals that appear within 8 months of the Hanjiang-to-Weihe River Diversion Project. The results show that the accuracy of the best framework in the improved model is 0.98, which is 0.1 higher than original model. The average precision, recall and F1 values of all improved models increased by 0.11, 0.12 and 0.12, respectively. Meanwhile, the improved model can visualize the entire waveform recognition process. A novel observation is that in some signal categories, the improved model mainly classified by focusing on the background information instead of the waveforms. It provides a reference for the intelligent classification of signals in MS monitoring engineering.
In the node-based smoothed finite element method (NS-FEM), the unknowns including displacement, stress and strain are all stored at element nodes, contributing to good numerical accuracy and implementation convenience of the method. For the geotechnical deformation analyses, however, NS-FEM may cause the non-physically oscillated deformation. In this work, the cause of the non-physical geotechnical deformation behavior associated with NS-FEM is investigated, and it is found that the non-physical geotechnical deformation is attributed to unevenness of the assembled stiffness in NS-FEM. To obviate the non-physical geotechnical deformation problem, the hybrid smoothed finite element method (HS-FEM), as a combination of finite element method (FEM) and NS-FEM, is applied. Based on a flexible strip footing resting on the ground of weightless soil, a linear elastic medium with a circular cavity and a two-layered soil slope, the applicability of HS-FEM(α) with adequate parameter α to geotechnical deformation and stability analysis is validated.
The limit equilibrium method, slice method and elastic mechanics method are adopted to investigate the mechanism of water inrush from the tunnel face induced by fault. Semi-analytical expressions of the minimum safety thickness of the rock resisting water inrush are derived. The safety thickness calculation method is applied to the actual tunnel engineering, and the accuracy of the proposed method is verified by comparing with the actual excavation results. On this basis, the minimum safety thickness affected by karst water pressure, fault dip, vertical force, width and shear strength indexes of the fault fracture zone are further analyzed and discussed. The results show that: 1) The minimum safety thickness increases with karst water pressure; 2) As the fault dip increases, the minimum safety thickness first increases and then decreases, and water inrush from the tunnel face is prone to occurring when the fault dip is between 45° and 60°; 3) The minimum safety thickness linearly increases with the width of fault fracture zone; 4) The minimum safety thickness linearly decreases with the increase of shear strength of the fault fracture zone; 5) The minimum safety thickness increases with vertical force on the fault fracture zone. The research results provide a new idea for calculation methods and theoretical research of water inrush in karst tunnel, which has certain reference significance and application value for similar projects.
Corrosion of rockbolt significantly affects the long-term serviceability of anchorage structures, resulting in premature failure of rock engineering. The corrosion and degradation mechanism for mortar grouted rockbolt is far from clear. In this paper, comprehensive experiments were carried out to investigate corrosion-induced degradation of rockbolt considering natural fracture and continuous load. Concrete-mortar-rockbolt specimens with an initial crack at different locations were made. Continuous axial loads were applied to the rockbolt by a puller system. The electrochemical method was employed to accelerate rockbolt corrosion. The bond — slip relationships for corroded specimens were obtained by the direct pull-out test of rockbolt. Further, the effects of natural fracture and continuous load on the corrosion characteristics, corrosion mechanism and bond performance degradation of rockbolt were discussed. Results show that corrosion of rockbolt significantly reduces the bond strength and critical slip displacement of rockbolt. The bond strength for the rockbolt with a corrosion degree of 3.45%–4.98% reduces by 39.5%–65.8% compared with that before corrosion. Corrosion of rockbolt is more prone to occur near the natural fracture. The closer the natural fracture to the loading end, the more severe the corrosion-induced bond degradation. The larger the axial load, the more significant the corrosion degradation.
Deep salt cavern gas storage is subjected to periodic high stress load during operation. To explore the damage and deformation characteristics of salt rock under triaxial cyclic loading and unloading, the MTS815 rock mechanics test system and acoustic emission (AE) signal acquisition system were used, and the effects of confining pressure and loading and unloading on the characteristics of AE and energy evolution of the whole cycle were analyzed. The results showed that: 1) as the confining pressure increased from 10 MPa to 30 MPa, the cumulative AE counts in the compaction stage decreased by 86%. Kaiser effect was obvious before the peak stress point, and the Felicity ratio was negatively correlated with the number of cycles; 2) With the increase of deviatoric stress, the growth rate of elastic energy(Uc) and dissipated energy(Ud) increased gradually. Under the same deviatoric stress, the deformation and dissipation energy of high confining pressure specimen were smaller, when it reached the same stress; 3) Both Uc and Ud showed two-stage growth trend during the test. At the same strain level, with the increase of confining pressure Uc and Ud increased as MnMolecular function, when the confining pressure effect strengthened. Considering the confining pressure, the coupling equation of AE ringing count and Ud during loading and unloading was established and verified. It has certain guiding significance for the safe operation of deep salt cavern gas storage.
In this paper, the creep property of shales is examined from two viewpoints: one is bedding orientation and the other is the water content. To investigate these effects, uniaxial creep tests were carried out on water-containing bedded shales. The creep curves were continuously observed with different water contents and bedding orientations. The correlations of water content and bedding angle with the transient elastic modulus and transient creep rate were constructed. The effects of bedding angle and water content were incorporated into the creep parameters of Burgers creep model, and the microscopic mechanism of water effect was interpreted based on mineral compositions due to rock-water interaction. The results revealed that the shale with a higher bedding angle had a higher transient elastic modulus and a lower transient creep rate. A higher water content triggered a lower transient elastic modulus and a higher transient creep rate.
Studying the energy dissipation characteristics of high-temperature rock after cooling with water during geothermal drilling construction is crucial to improving rock crushing efficiency. The energy dissipation characteristics of granite were investigated by conducting dynamic tests with a split Hopkinson pressure bar (SHPB) system under different impact loadings. The granite specimens were subjected to temperatures from 25 °C to 1000 °C. The micromorphology and pore distribution of granite were obtained by scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests. The porosity change trend could be divided into two stages at 400 °. The micropores and small pores accounted for over 75.0% before 400 °C The medium pore proportion increased rapidly when T≽400 °C. In addition, the dynamic peak stress and peak strain increased with incident energy, while the trend of the change in the dynamic elastic modulus was not apparent. The proportion of dissipated energy showed an upwards trend when the heating temperature varied from 25 °C to 800 °C, while the absorbed energy of granite heated to 1000 °C decreased. The energy utilization efficiency was the highest when the strain rate was between 100 s−1 and 120 s−1.
In previous research on railway traffic safety in subgrade sections, the physical parameters of foundation soil are often considered deterministic parameters. To explore the influence of the stochastic field characteristics of the soil around the shield tunnel of the subway on the traffic safety of the existing railway on the ground, an analytical model of the train-track-shield tunnel-foundation soil coupling system was established. The physical and mechanical parameters of the foundation soil are randomly assigned based on the stochastic field theory, and the probability density evolution information of the dynamic responses of the train such as the wheel load reduction rate (WLRR) and the carriage acceleration are obtained. Based on the probability density evolution theory, the dynamic response analysis of the train running on the ground under the deformation condition for shield tunnel construction is carried out. The main results show that: the distribution of ground settlement in the shield tunnel construction section is approximately normal distribution, the maximum value of the mean value and standard deviation of the ground settlement both appear at the centerline of the shield tunnel, while the maximum value of WLRR appears in the descending segment on both sides of the peak of the ground settlement. When the train speed increases, the width of distribution of the vertical acceleration probability density contour line of the carriage body gradually increases, and the corresponding probability density distribution when the upper limit of the vertical acceleration takes the maximum value is still approximately normal. The distribution range of WLRR exceeds the limit requirement of 0.8 at the train running speed reaching 300 km/h. The carriage body acceleration meets the requirement of 1.3 m/s2 under the condition of train speed below 300 km/h. In order to meet the traffic safety guarantee rate of 99.74%, which is three times the standard deviation, it is recommended that the running speed of ground train in the shield tunnel construction section does not exceed 250 km/h.
When constructing a long undersea tunnel, cross-sectional area of some parts of the tunnel will be changed to strengthen the tunnel or save construction costs, which will cause a change in aerodynamic characteristics of the tunnel. By comparing variable cross-section(VCS) tunnel and constant cross-section (CCS) tunnel, the influence of abrupt cross-section on pressure transients and slipstream in the long tunnel was studied. The RNG k-ε turbulence model was adopted for numerical simulation, which was validated by the moving model test. The results show that the closer it to the abrupt cross-section, the larger the difference between the positive peak pressure of the VCS tunnel and that of the CCS tunnel, reaching a maximum of 7.63% at 5.43 km. The difference in slipstream velocity in the longitudinal direction between the two tunnels can reach 18.7% at most, but it is almost the same in the other two directions. In addition, the impact of the abrupt section on slipstream in different areas of the tunnel is different. This research has an important reference value for parameter design of long variable cross-section tunnel and layout of auxiliary facilities in tunnel.