Numerical Simulation Software Research Articles

Thickness and Strength Analysis of Prestressed Anchor (Cable) Compression Arch Based on Safe Co-Mining of Deep Coal and Gas

The stability of the gas extraction roadway is very important for the safe mining of coal and gas. The compression arch formed by the combined action of the prestressed bolt (cable) support and surrounding rock has been widely used in the engineering practice of the gas extraction roadway. It is of great engineering application value to analyze the influence of prestressed bolt (cable) parameters on the compression arch. In this paper, combined with the engineering practice of the deep roadway in Huainan and Huaibei mining area of Anhui Province, the mechanical parameters of surrounding rock are measured via field coring and the laboratory. The numerical simulation software FLAC3D is used to analyze the typical position of fractured mudstone, mudstone, sandy mudstone and muddy sandstone under the bolt pre-tightening force of F = 50 kN, 70 kN and 100 kN; the bolt spacing of a × b = 400 mm × 400 mm, 500 mm × 500 mm and 600 mm × 600 mm; the bolt length of L = 1500 mm, 2000 mm, 2600 mm and 3000 mm; and the distribution characteristics of additional compressive stress on the surface of the side. The influence of the different lithology and bolt parameters on the thickness and strength of the compression arch was analyzed, and on this basis, prestressed anchor cables with a pre-tightening force of F = 80 kN, 100 kN and 120 kN and length of L = 3000 mm, 4000 mm and 6000 mm were applied, and their influence on the thickness and strength of the compression arch was analyzed. The results show that the bolt pre-tightening force (F) and the bolt length (L) have a significant effect on the thickness of the compression arch, while the surrounding rock lithology, the bolt spacing (a × b), the anchor cable pre-tightening force (F) and the anchor cable length (L) have no obvious effect on the thickness of the compression arch. The surrounding rock lithology, the bolt pre-tightening force (F), the bolt length (L), the bolt spacing (a × b), the anchor cable pre-tightening force (F) and the anchor cable length (L) have a significant effect on the strength of the compression arch.

Finite Element Analysis of Dynamic Recrystallization Model and Microstructural Evolution for GCr15 Bearing Steel Warm-Hot Deformation Process.

Warm deformation is a plastic-forming process that differs from traditional cold and hot forming techniques. At the macro level, it can effectively reduce the problem of high deformation resistance in cold deformation and improve the surface decarburization issues during the hot deformation process. Microscopically, it has significant advantages in controlling product structure, refining grain size, and enhancing product mechanical properties. The Gleeble-1500D thermal-mechanical physical simulation system was used to conduct isothermal compression tests on GCr15 bearing steel. The tests were conducted at temperatures of 600-1050 °C and strain rates of 0.01-5 s-1. Based on the experimental data, the critical strain model and dynamic recrystallization model for the warm-hot forming of GCr15 bearing steel were established in this paper. The model accuracy is evaluated using statistical indicators such as the correlation coefficient (R). The dynamic recrystallization model exhibits high predictive accuracy, as indicated by an R-value of 0.986. The established dynamic recrystallization model for GCr15 bearing steel was integrated into the Forge® 3.2 numerical simulation software through secondary program development to simulate the compression process of GCr15 warm-hot forming. The dynamic recrystallization fraction was analyzed in various deformation regions. The grain size of the severe deformation zone, small deformation zone, and difficult deformation zone was compared based on simulated compression specimens under the conditions of 1050 °C and 0.1 s-1 with the corresponding grain size obtained with measurement based on metallographic photos; the relative error between the two is 5.75%. This verifies the accuracy of the established dynamic recrystallization and critical strain models for warm-hot deformation of GCr15 bearing steel. These models provide a theoretical basis for the finite element method analysis and microstructure control of the warm-hot forming process in bearing races.

Research on key influencing factors of scrap tire-soil retaining wall

The emergence of STSW can reduce the amount of materials such as sand and gravel and improve its performance compared to conventional retaining walls. In order to investigate the key influencing factors of STSW, the compression modulus of Scrap tire-soil module (STSM) was obtained by designing a full-scale compression strength test. The shear strength was obtained through a scale-test of shear strength. On this basis, the gravity STSW was established by the finite element numerical simulation software, and the bearing capacity of STSW was analyzed. Further, the key influencing factors of the bearing capacity of STSW were analyzed by designing orthogonal tests, and suggestions for parameter selection for designing STSW were given. The results show that: the friction angle of STSW increases and becomes larger with the increase of area ratio, and the cohesion decreases and decreases with the increase of area ratio; with the increase of compression modulus and internal friction angle, the maximum shear stress inside the retaining wall increases, while the cohesive force has almost no effect on the maximum value of shear stress inside the retaining wall; when constructing retaining walls, it is recommended to use Internal filling material with large compression modulus, small area ratio and its in the range of [0.3–0.5] of STSM.

Stress analysis for an arbitrary-shaped tunnel in orthotropic rock masses based on a simple mapping function

Most natural rock masses are anisotropic, but there is no simple and effective method to quickly and accurately calculate the stress at any point in the tunnel with an arbitrary shape in orthotropic rock masses. In this paper, first, the hole shapes of the z1- and z2-planes are calculated from the hole shapes of the z-plane, and then the outer regions of these two planes are mapped to the ζ1- and ζ2-planes, respectively, and an efficient algorithm to determine the mapping function is provided. After mapping, the stress boundary conditions originally expressed by z as the independent variable are transformed into ζ1 and ζ2 as the independent variables, posing new difficulties to the solution of the stress boundary condition. To solve the stress boundary conditions, in this paper, the power series solution and the boundary collocation method are proposed, and two complex potential functions expressed by series are obtained. The stress and displacement of each point on and outside the hole can be easily calculated because the form of the two mapping functions is simple. Finally, the correctness of this method is evaluated by comparing the stress calculated using this method with the stress calculated using the previous methods and numerical simulation software.

Numerical Simulation for Optimization of the Water Intake-Outlet Arrangements for Seawater Desalination Plants Based on MIKE21: A Case Study of Laoshan Bay, Qingdao

The field of seawater desalination faces some challenges. For example, at present, site selection and layout of water intakes and outlets are often not carefully considered. This can easily result in the degradation of water quality due to coastal sea pollution and sudden brine discharge, which can be hazardous and can negatively impact marine development and activities such as aquaculture. By using the MIKE21 numerical simulation software, this paper establishes a two-dimensional mathematical tidal current model of the engineered sea area and a mathematical convection diffusion model after brine discharge. The tidal current field of the Laoshan Bay waters and the salinity field distribution after brine discharge in different water intake-outlet arrangement schemes in desalination plants are calculated and analyzed. In view of the various control factors affecting the layout and location selection of water intakes and outlets, combined with the current situation of marine development and utilization, calculation results and layout advantages and disadvantages of the primary schemes are compared and analyzed, the scheme with the best water intake-outlet layout is recommended, and relevant optimization suggestions are presented.

Performance optimization of efficient PbS quantum dots solar cells through numerical simulation

Colloidal quantum dots (CQDs) solar cells are less efficient because of the carrier recombination within the material. The electron and hole transport layers have high impact on the performance of CQDs based solar cells which makes its investigation a very important component of the development of the more efficient devices. In this work, we have tried performance optimization in tetrabutyl ammonium iodide capped lead sulfide (PbS) CQDs (PbS-TBAI) as absorber layers based solar cells by incorporating different hole transport layers (HTLs) to achieve better power conversion efficiency (PCE) in different device architectures by SCAPS—1D numerical simulation software. It was observed from the simulation that the ITO/TiO2/PbS-TBAI/HTL/Au device architecture shows higher power conversion efficiency as compared to the conventional experimentally realized device architecture of ITO/TiO2/PbS-TBAI/PbS-EDT/HTL/Au. The influence of interface defect density (IDD) at the interface TiO2/PbS-TBAI has also been studied where IDD is varied from 1 × 1013 cm−2 to 1 × 1018 cm−2 while keeping the rest of the device parameters intact. The result shows a noteworthy reduction in the PV performance of the device at higher IDD. This modelled device structure provides a new direction toward the experimental realization in high efficiency PbS QDs solar cells.

Study on the influences of the fractal dimension of the root system and slope degree on the slope stability

The problem of quantifying the effect of the alfalfa root morphology on the stability of the shallow surface layer of the slope of the Haizhou open-pit coal mine and the optimal slope degree in terms of the reinforcement of the shallow surface layer by the alfalfa root system was addressed. In this study, the mechanical parameters of plain soil and alfalfa root–soil composite samples were measured by indoor soil tests and triaxial compression tests, and a calculation model for the slope of the Haizhou open-pit coal mine was established in FLAC3D numerical simulation software to analyze the influence of the alfalfa root system on the maximum displacement of the shallow surface layer of the slope and the relationship with the fractal dimension of the alfalfa root system. The fractal dimension was applied to quantify the influence of the alfalfa root morphology to further investigate the relationship between the fractal dimension of the root system and the optimal slope of the shallow surface layer. The analysis showed that the fractal dimension of the alfalfa root system varied at different slope degrees, i.e., 40° > flat > 30° > 50°; the maximum soil displacement of the shallow surface layer of the slope increased with slope in nonlinear increments. Analysis of the fractal dimension of the alfalfa root system and the maximum displacement reduction rate at the different slope degrees revealed that the optimal slope degree of the shallow surface layer reinforced by alfalfa varied between 30° and 40°. The study results could provide a basis for further explaining the nature of the role of the alfalfa root morphology in reinforcing shallow surface soil and the optimal slope degree of the slope of the Haizhou open-pit coal mine reinforced by alfalfa roots.

Resistance element welding of aluminium alloy and steel using an element of aluminium

Aluminium alloy AA6061 and mild steel Q235 were welded by resistance element using an aluminium rivet as the element. The microstructure and properties of the joints were characterised. The temperature distribution on the cross-section of the joints was calculated by using ABAQUS numerical simulation software. The observation results on the cross-section of the joints show a nugget formed at the interface between the rivet tip and steel of lower plate. The maximum tensile shear load of the joints reached 5.82 kN at the welding current of 26 kA. This study reveals that the bearing interface of the resistance element welded joint between aluminium alloy and mild steel is like-to-like interface of aluminium alloy which strengthens the joint.

О звукоизлучении корпусов морской техники под действием силы на низких частотах

Object and purpose of research. This paper discusses induced noise radiation into water from spherical uniform bodies and spherical shells to estimate the acceptability of commonly used simplified approach to prediction of low-frequency acoustic signatures for marine objects. Materials and methods.The calculations were performed as per analytical expressions and numerical simulation techniques (FEM). Main results. The study has shown that increasing the density of radiating body and increasing mechanical resistance of shell at the location of exciting force reduces noise radiation. Resonant noise radiation typically occurs due to structural non-uniformities of marine objects, like local masses needed to ensure zero buoyancy, e.g. equipment or ballast. These nonuniformities create reactive forces that reach their peak values at resonant frequencies of the hull. Conclusion. The study concludes that reliable computational estimate of low-frequency acoustic signatures must take into account both mechanical resistance and non-uniform distribution of masses along hull, which can be done in numerical simulation packages.

Risk Assessment and Water Inrush Mechanism Study of Through-Type Fault Zone Based on Grey Correlation Degree

In order to effectively prevent and control the problem of water inrush from the through-type fault floor, based on the analysis of the case data of water inrush from the fault structure in the Fengfeng mining area, the types of karst water inrush from the floor are divided into 3 categories, 6 subcategories, and 17 fine categories. Four water inrush modes are summarized: composite structure water inrush, through-type fault water inrush, roof crack expansion water inrush, and floor vertical crack expansion water inrush. Based on the grey correlation theory and combined with the Analytic Hierarchy Process (AHP), this paper evaluates the water inrush risk of the F55-1 through-type fault zone from a micro individual perspective, taking the Xin’an Mine as the engineering background. Based on the water–rock coupling theory, the FLAC3D numerical simulation software is applied to study the disaster mechanism of the water inrush mode of the through-type fault. Through analyzing the changes of primary fracture stress and displacement of the intact floor strata and the aquifuge, and the pressure changes of confined water in fault zones, the collaborative water inrush mechanism of the damage and fracture of the bottom plate rock layer, the expansion and connection of the original fracture, and the seepage and progressive intrusion of the pressure water during the advancing process of the working face is analyzed. The research results indicate that the evaluation result of the water inrush risk of the F55-1 through-type fault in Xin’an Mine is Level I, belonging to the high risk and consistent with the actual situation model, verifying the rationality of the evaluation model. The process of water inrush in the numerical model is summarized as follows: a rock pressure failure zone is caused by the rupture and instability of floor aquifuge; a progressive intrusion zone develops—water inrush is connected between rock pressure failure zone and progressive intrusion zone; floor lagging flood occurs. Under the combined action of mine pressure and confined water pressure, the progressive intrusion height of confined water is significantly increased. The research results have important reference basis for future coal mining planning. This provides engineering reference and practical experience for the prevention and control of water damage in structured bottom plates under similar conditions.

Prediction of the Penetration Radius of Cumulative Blasting.

To improve the efficiency of coal seam gas extraction, the influence characteristics of different factors on the penetration effect of cumulative blasting were determined and the hole spacing was effectively predicted; in this work, we used ANSYS/LS-DYNA numerical simulation software to establish the penetration model of cumulative blasting. Combined with an orthogonal design scheme, the crack radius prediction of cumulative blasting was studied. A prediction model for predicting the fracture radius of cumulative blasting based on three groups of different factors was established. The results showed that the primary and secondary order of factors that affected the fracture radius of cumulative blasting was as follows: ground stress > gas pressure > coal firmness coefficient. The penetration effect decreased with increasing ground stress and decreased with an increase in the gas pressure and coal firmness coefficient. The industrial field test was carried out. The gas extraction concentration increased by 73.4% after cumulative blasting, and the effective crack radius of cumulative blasting was approximately 5.5-6 m. The maximum error of the numerical simulation was 1.2%, and the maximum error of the industrial field test was 6.22%, which proved that the crack radius prediction model of cumulative blasting was correct.

Case Study on the Effect of Delay-Time Differences between Columns during Blasting Demolition of RC Structures with a Small Height-to-Width Ratio

Blasting demolition plays an important role in building demolition, and numerical-simulation methods can facilitate the optimization of blasting-demolition schemes. To study the influence of the delay-time differences between columns on the blasting and demolition effect of small-aspect-ratio reinforced concrete structures, a separated common node model of small-aspect-ratio structures was established through the finite element numerical simulation software ANSYS/LS-DYNA. The results showed that the delay-time differences between columns influenced the position of the plastic hinge of the structure, and the plastic hinge was located at the end of the back span beam when the delay-time difference was 0.1~0.3 s. The plastic hinge moves to the top of the back row of the columns of the first floor at 0.4~0.8 s and to the end of each span of the beams at 0.9 s. When the plastic hinge is at the end of the beam, the orientation axis is located at the bottom of the back row of the columns of the first floor. Moreover, when the plastic hinge is at the top of the back row of the columns of the first floor, the orientation axis is at the same position as the plastic hinge. The delay-time difference also affects the recoil distance of the structure as well as the height of the burst pile. To ensure that the structure can be successfully collapsed under the preconditions of disintegration, for a small height-to-width ratio structure, the appropriate intercolumn delay-time difference is 0.4~0.5 s.

Numerical Simulation of High Power Microwave Coupling to Typical Individual Inertial Device

HPM (high-power microwave) weapons become the major threat to individual equipment which is developing to be unmanned and intelligent. A typical inertial device of individual equipment is taken as the research object to find out its coupling paths based on the analysis of function and structural characteristics, and the effects of HPM coupling to the typical inertial device are simulated by the numerical simulation software CST. The results shows that power and signal cables of MEMS (Micro-Electro-Mechanical System) accelerometer are the main coupling paths of HPM; The power cable has size coupling effect which is strongest when the sum of the cable length and twice the distance to the “ground” is equal to odd times of quarter wavelength, and weakest when the cable length is equal to even times of quarter wavelength; The signal cable has wavelength coupling effect that is positively correlated with cable length which is less than wavelength, and not affected by cable length which is greater than wavelength; The screen in signal cable not only greatly reduces the peak value of coupling voltage, but also effectively reduces the influence of cable length on the coupling effect. The research results provide support for the protection of individual inertial devices, and also provide a reference for the design of HPM weapons.

Determination Method for the Strength Model of a Jointed Rock Mass Based on the Geological Strength Index

The mechanical characteristics of materials are the key to numerical calculation, the determination of material parameters of jointed rock mass is conundrum in academia. For the purpose of more efficiently and accurately select the mechanical parameters of the jointed rock masses, in this paper, a new method is proposed which for constructing a numerical model of jointed rock masses, which based on the Geological Strength Index (GSI) and the principles of damage mechanics. With the help of basic concepts of damage mechanics, the joint equivalent coefficient is proposed, establishing the relationship between GSI and joint spacing. The selection way for the mechanical parameters of a jointed rock masses is given in combination with the Hoek-Brown strength criterion. Then, a numerical calculation model is constructed by utilizing 3DEC numerical simulation software to discuss the stability of the adjoining rock under the condition of different GSIs, which is successfully applied to the Wangjialing coal mine project. The numerical results match quite closely with the field conditions, the maximum error is 18%, the minimum error is 5.6%, verifying the rationality and accuracy of this way and providing a new way for the accurate numerical simulation of jointed rock masses.

A bendable wide oblique incident angle stable polarization insensitive metamaterials absorber for visible optical wavelength applications

In the visible frequency range, the most common application is for the transmission of electromagnetic signals over air and time to an aerial receiver. They are implemented to check tapped live powered components as well as identify defects, thermal leaking hot spots, or electrical failures. This study investigates the use of a compact nonagon-shaped metamaterial absorber (MMA) for wideband visible applications by employing a three-layer substrate material structure consisting of metal, dielectric, and metal. In comparison to the most current study, the presented MMA has a smaller size, which represents a noticeable novelty. Moreover, the proposed MMA has bendable properties and two numerical simulation software have been used to validate the proposed MMA. This demonstrates the successful acquisition of data from both the CST and HFSS simulations. The proposed metamaterial absorber attained above 80% absorption in the visible ranges from 400 nm to 750 nm wavelength for the simulation mode of TE and TM, respectively. An overall unit cell size of 930 × 930 × 202 nm3 which achieves an average absorption of 95.61% in its operating band 519–677 nm for visible optical wavelength when the performance of the proposed MMA was verified using the HFSS software. Moreover, the constant absorption feature is stable over a large range of oblique incidence angles. The quality of the MMA is verified by assessing the PCR value. Wide-angle incidence angle stability, polarization insensitivity, and absorption with 15⁰ bending effects can all be observed in both modes (TM and TE). In addition, the absorption property of MMA was investigated structurally by applying electric and magnetic fields. The presented MMA can be used in wide-angle stability, MRI, color imaging, solar cells, thermal imaging, and so on.

Coal mine gas migration model establishment and gas extraction technology field application research

Gas drainage is the main technical measure to prevent and control coal and gas disasters. Reasonable extraction parameters can improve extraction efficiency and reduce the risk of gas accidents. In order to further study the influence of extraction parameters on gas drainage effect, this paper combines COMSOL Multiphysics numerical simulation and field experiment to optimize the two parameters of intubation spacing and extraction negative pressure in goaf of 42,201 working face in Buertai Coal Mine, Inner Mongolia. The three-dimensional gas distribution model in goaf was established, and the COMSOL numerical simulation software was used for calculation. Combined with the field experiment, the influence of intubation spacing and extraction negative pressure on the extraction effect was obtained. The results show that in the range of 50 m-70 m, the drainage effect is ideal when the negative pressure is 12–18 kPa.

Analysis and verification of stress and plastic zone in surrounding rocks of hydraulic flushing borehole based on strain-softening

This study aimed to solve the problem ignored by previous research on hydraulic flushing gas extraction technology regarding the strain-softening of surrounding rock. Firstly, through the analysis of experimental data, previous studies have proved that the essence of strain-softening is that the internal friction angle remains unchanged while the cohesion decreases. According to the variation law of cohesion of surrounding rocks in a borehole, we theoretically analyzed the stress distribution of the surrounding rock considering strain-softening and determined the theoretical formula of the plastic zone radius. Subsequently, we established a numerical calculation model considering strain-softening using the COMSOL numerical simulation software. We simulated the influence of residual cohesion on the stress and plastic zone of surrounding rocks of the borehole. We found that with the decrease in residual cohesion, the peak stress transferred to the deep and the plastic zone radius gradually increased. The simulation results were compared with the theoretical values, and the errors were found to be within 10%, which verifies the model's accuracy. Subsequently, we studied the influence law of strain-softening on the stress and plastic zone of surrounding rocks of boreholes with different radii. We found that the larger the borehole radius, the greater the influence of strain-softening. The field measurement results show that the stress reduction zone of a hydraulic flushing borehole is about 10 times the borehole radius. The stress reduction zone calculated without considering strain-softening is 1.305 times the borehole radius, and that calculated while considering strain-softening is 6.663 times the borehole radius. Thus, we proved that strain-softening is an essential factor affecting the stress distribution of surrounding rocks of the borehole. When studying the gas extraction through a hydraulic flushing borehole, it is necessary to consider the strain-softening of surrounding rocks.

Dynamic Response Law and Failure Mechanism of Slope with Weak Interlayer under Combined Action of Reservoir Water and Seismic Force

The southwestern region of China is close to the Eurasian earthquake zone. Many engineering areas in southwestern China are affected by earthquakes and are close to the epicenter of earthquakes that occur in this region. During earthquakes, slopes with weak interlayers are more likely to cause large-scale landslides. In response to the low stability of slopes with weak interlayers in reservoir dam areas, the dynamic response law and failure mechanism of weak interlayered slopes under the combined action of reservoir water and seismic forces were studied through shaking table model tests and finite element numerical simulation software. The height of the water level and the size of the seismic waves were changed during these tests. The research results indicate that seismic waves are influenced by weak interlayers and are repeatedly superimposed between the weak interlayers and the slope surface, resulting in an acceleration amplification effect that increases by approximately 1.8 times compared to homogeneous slopes. Vertical earthquakes have a significant impact on the dynamic response of slopes, and their peak acceleration amplification coefficient can reach 0.83 times the horizontal peak acceleration. The stability of weak interlayers during earthquakes is the worst within the range of the direct action of reservoir water. The failure mode of a slope is as follows: earthquake action causes cracking in the upper part of the slope, and as the earthquake increases in intensity, and the infiltration of reservoir water intensifies, the cracks expand. The soft and muddy interlayer in the front section of the slope forms a sliding surface, and ultimately, the sliding failure forms an accumulation body at the foot of the slope. In reservoir dam areas, the stability of a slope is closely related to the engineering safety of the reservoir dam. Therefore, when a strong earthquake and the water level in a reservoir jointly affect a weak-interlayer slope, the slope is in the stage of plastic deformation and instability. The stability of the slope may be overestimated, and the slope is likely vulnerable to sliding instability, which needs to be monitored and treated.

Experimental study on dynamic mechanical and failure behavior of a jointed rock mass

In order to study the dynamic mechanics and failure behavior of jointed rock masses, impact tests were carried out on sandstone specimens with intersected jointed and unjointed intact sandstone specimens using a modified split Hopkinson pressure bar (SHPB) with confinement. The effects of intersected artificial joints on the dynamic properties and failure mechanism of sandstone samples were analyzed. The dynamic stress-strain curve of sandstone specimen was obtained from the test, as well as the fracture failure behavior of specimen under different loading rates and confining pressures. The results show that the dynamic compressive strengths of the unjointed intact rock specimens and the jointed rock specimens both increase with the increase of the loading rate and the confining pressure. With the increase of loading rate, the jointed rock specimens showed more obviously plastic deformation ability than the intact rock specimens, and the size of the broken pieces of the jointed rock samples became smaller. The dynamic failure modes of the jointed rock samples are irregular and mainly appear tensile and compressive shear failures. Next, the dynamic initiation and development process of cracks in the jointed rock specimens were analyzed by using the UDEC numerical simulation software. The process of initiation and development of meso-cracks is affected by intersected joints. Combined with the effective stress contour map, five typical crack types are defined to reveal the macroscopic fracture behavior of sandstone samples.

Size Effects of Rough Fracture Seepage in Rocks of Different Scales

Percolation experiments were conducted on coal samples with various fracture lengths and inclination angles under different stress conditions using a gravity-loaded rock percolation test device. The goals of these experiments are (1) to improve the technology for protecting water resources while mining coal and (2) to enhance the research on how the size effects of fracture affect seepage. A three-dimensional seepage model was constructed using COMSOL numerical simulation software for larger fracture lengths ranging from 1 to 30 m to investigate the seepage pattern under the coupling of fracture roughness, fracture width, and other factors. Multiple regression analysis was used to investigate the effects of different factors on seepage from large and small fractures independently. The results show that, under laboratory conditions, for fracture lengths 10–70 mm (small length), permeability increases non-linearly with an increase in fracture length, and the overall increase is approximately 1.8 times. Whereas, for fracture lengths of 1–30 m (large length) in the simulation, permeability decreases and then increases with an increase in fracture length, and the overall change is approximately 0.03 times. The permeability varies in three stages (1–8 m obvious change, 8–23 m stabilization, 23–30 m stability) under different fracture lengths, widths, and roughness conditions. Acritical size was found to exist. The effect of fracture length on large length fracture seepage and small length fracture seepage was further verified by parameter sensitivity. The results of this study further reveal the mechanism of fracture seepage under coupling of fracture geometry size stress.