Carbon Carbon(C/C)composites in thermal-protection system are exposed to severe thermochemical ablation and mechanical erosion,and their thermal-protection performance is of vital importance to the structural safety a...Carbon Carbon(C/C)composites in thermal-protection system are exposed to severe thermochemical ablation and mechanical erosion,and their thermal-protection performance is of vital importance to the structural safety and flight status of hypersonic vehicles.We numerically analyzes the mesoscopic ablation-erosion of C/C Composites with Inclined Fibers(CCIF).First,a thermochemical ablation model describing the reaction-diffusion coupled problem of C/C composites on mesoscale is employed to analyze ablative process,and the corresponding surface ablation morphology is obtained.Then,the ablation morphology of CCIF is taken as the geometrical model for mechanical erosion analysis,and their damage and failure behavior under high-speed airflow shear is analyzed by using progressive damage method.Moreover,the effects of fiber inclined angle and airflow direction on the mechanical erosion of CCIF are investigated,and the ablationerosion behavior is analyzed and discussed.The results show that the failure modes of mechanical erosion in inner and edge regions are obviously different,showing granular and block erosion phenomena respectively.The mechanical erosion of CCIF in the direction of reverse flow is easier than that in the direction of forward flow.These results can provide a theoretical basis for the design and optimization of thermal protection system materials.展开更多
When the expressway crosses the goafs inevitably,the design is generally to build the road on coal pillars as much as possible.However,the existing coal pillars are often unable to meet relevant requirements of highwa...When the expressway crosses the goafs inevitably,the design is generally to build the road on coal pillars as much as possible.However,the existing coal pillars are often unable to meet relevant requirements of highway construction.Combining three-dimensional physical model tests,numerical simulations and field monitoring,with the Urumqi East Second Ring Road passing through acute inclined goafs as a background,the deformation and failure mechanism of the overlying rock and coal pillars in acute inclined goafs under expressway load were studied.And in accordance with construction requirements of subgrade,comprehensive consideration of the deformation and instability mechanism of acute inclined goafs,the treatment measures and suggestions for this type of geological disasters were put forward.The research results confirmed the rationality of coal pillars in acute inclined goafs under the expressway through grouting.According to the ratio of diff erent overlying rock thickness to coal pillar height,the change trend and value of the required grouting range were summarized,which can provide reference for similar projects.展开更多
Magnetohydrodynamic(MHD)radiative chemically reactive mixed convection flow of a hybrid nanofluid(Al_(2)O_(3)–Cu/H_(2)O)across an inclined,porous,and stretched sheet is examined in this study,along with its unsteady ...Magnetohydrodynamic(MHD)radiative chemically reactive mixed convection flow of a hybrid nanofluid(Al_(2)O_(3)–Cu/H_(2)O)across an inclined,porous,and stretched sheet is examined in this study,along with its unsteady heat and mass transport properties.The hybrid nanofluid’s enhanced heat transfer efficiency is a major benefit in high-performance engineering applications.It is composed of two separate nanoparticles suspended in a base fluid and is chosen for its improved thermal properties.Thermal radiation,chemical reactions,a transverse magnetic field,surface stretching with time,injection or suction through the porous medium,and the effect of inclination,which introduces gravity-induced buoyancy forces,are all important physical phenomena that are taken into account in the analysis.A system of nonlinear ordinary differential equations(ODEs)is derived from the governing partial differential equations for mass,momentum,and energy by applying suitable similarity transformations.This simplifies the modeling procedure.The bvp4c solver in MATLAB is then used to numerically solve these equations.Different governing parameters modify temperature,concentration,and velocity profiles in graphs and tables.These factors include radiation intensity,chemical reaction rate,magnetic field strength,unsteadiness,suction/injection velocity,inclination angle,and nanoparticle concentration.A complex relationship between buoyancy and magnetic factors makes hybrid nanofluids better at heat transmission than regular ones.Thermal systems including cooling technologies,thermal coatings,and electronic heat management benefit from these findings.展开更多
The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined ...The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method.Field monitoring was conducted to assess the load and deformation of the initial support structure,and on-site investigations identified the distribution of cracked areas.In addition,numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure,which were then compared with field observations for validation.The variations in the lateral pressure coefficient and water pressure were evaluated.The results revealed that damage was primarily concentrated in the shoulder,spring line,and knee areas,with the bending moment at the knee increasing by up to 66.9%.The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support.Post-treatment analysis indicated significant reductions in axial force and bending moment,enhancing structural stability.These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulicpressure railroad tunnels.展开更多
The“upper coal and lower bauxite”resource distribution pattern is widespread in China,where mining of the overlying coal seam significantly alters the stress environment of the underlying bauxite layer.This study in...The“upper coal and lower bauxite”resource distribution pattern is widespread in China,where mining of the overlying coal seam significantly alters the stress environment of the underlying bauxite layer.This study investigates the stability of inclined bauxite pillars under the influence of stress redistribution caused by coal seam extraction.A theoretical model is developed to calculate the direction and magnitude of principal stresses in the inclined floor strata,and a pillar stability analysis model is established that considers the effect of principal stress rotation.The research employs a combination of theoretical analysis,physical modeling,numerical simulation,and field observation.Findings indicate that stress rotation is most pronounced at both ends of the coal seam goaf,with the maximum clockwise and counterclockwise rotation angles of 19°and-40°,respectively,observed in the bauxite layer.Inclined bauxite pillars are subjected to combined compressive and shear loading.Under such conditions,clockwise rotation of principal stress increases the shear-to-normal stress ratio,thereby reducing pillar stability.Pillars located beneath the coal wall are the first to fail due to stress concentration and principal stress rotation,which can trigger a cascade of instability among the adjacent pillars.The findings provide a theoretical basis and practical guidance for ensuring the safe co-mining of coal seams and bauxite resources.展开更多
In this paper,the authors examine various slip effects on themagnetic field and thermal radiative impacts on the flow,mass and heat transfer of a Jeffrey nanofluid over a 2-dimensional inclined stretching sheet by a p...In this paper,the authors examine various slip effects on themagnetic field and thermal radiative impacts on the flow,mass and heat transfer of a Jeffrey nanofluid over a 2-dimensional inclined stretching sheet by a porous media.The offered work is modelled to be in the form of a combination of coupled highly nonlinear partial differential equations in dimensional contexts.Governing equations were obtained,dimensionless parameters were defined in terms of similarity parameters,and the solutionswere obtained by the Homotopy Analysis Method(HAM).The analysis is significant as the effects of viscosity are identified and the important parameters are to be determined that could eventually control a type of flowbehaviour,especially in promoting the flowand inhibiting flowof velocity,temperature,and concentrations.The findings show that such an increase in themagnetic parameter decreases the velocity profile by approximately 15%due to more Lorentz forces,and thermal radiation increases the temperature profile by up to 25%,therefore,enhancing the rate of heat transfer.The process of Brownian motion and thermophoresis increases the depth of the thermal boundary layer by 10–20 percent and reduces in concentration profiles by 12 percent when the Brownian motion parameter increases.A velocity slip parameter lowers the velocity field by about 18 percent,and a parameter of permeability lowers the momentum of flow by another 10 percent.The HAM solutions show very high accuracy levels,having an order of convergence at level 15 and errormargins are well below 0.01 percent compared to the earlier studies.All these findings can provide profound knowledge in improving heat transmission in non-Newtonian fluid systems and can be used in biomedical engineering,thermal insulation,and industrial processes such as polymer extrusion and cooling technology.Principles of heat and mass transfer give us the crucial foundation on which to study the behavior of heat andmaterial flows in other engineering and scientific disciplines.Such principles apply to various fields of study,including the following engineering fields:mechanical,chemical,aerospace,civil,and environmental.展开更多
Because of actual requirement,shield machine always excavates with an inclined angle in longitudinal direction.Since many previous studies mainly focus on the face stability of the horizontal shield tunnel,the effects...Because of actual requirement,shield machine always excavates with an inclined angle in longitudinal direction.Since many previous studies mainly focus on the face stability of the horizontal shield tunnel,the effects of tensile strength cut-off and pore water pressure on the face stability of the longitudinally inclined shield tunnel are not well investigated.A failure mechanism of a longitudinally inclined shield tunnel face is constructed based on the spatial discretization technique and the tensile strength cut-off criterion is introduced to modify the constructed failure mechanism.The pore water pressure is introduced as an external force into the equation of virtual work and the objective function of the chamber pressure of the shield machine is obtained.Moreover,the critical chamber pressure of the longitudinally inclined shield tunnel is computed by optimal calculation.Parametric analysis indicates that both tensile strength cut-off and pore water pressure have a significant impact on the chamber pressure and the range of the collapse block.Finally,the theoretical results are compared with the numerical results calculated by FLAC3D software which proves that the proposed approach is effective.展开更多
A sealed portal could significantly alter the flame shape and smoke flow characteristics in inclined tunnel fires.In inclined tunnels,two typical sealing conditions could be defined,namely the upper portal sealed and ...A sealed portal could significantly alter the flame shape and smoke flow characteristics in inclined tunnel fires.In inclined tunnels,two typical sealing conditions could be defined,namely the upper portal sealed and the lower portal sealed.In this study,the effects of tunnel slope on flame shape,flame length,along with smoke mass flow rate and induced velocity at the tunnel portal,are numerically investigated.The results show that,in all scenarios,flames initially rise vertically but tilt toward the sealed portal during the quasi-steady stage,with the largest tilt angle observed in tunnels sealed at the lower portal.The slope significantly affects the flame tilt angle.The flame tilt angle in tunnels with the lower portal sealed varies irregularly with the slope,while it decreases as the slope increases in tunnels with the upper portal sealed.Subsequently,the smoke mass flow rate and induced velocity at the tunnel portal are analyzed in detail.Drawing on the obtained data,the flame length prediction models for impinging flames and non-impinging flames under different sealing conditions are developed,along with dimensionless models for smoke mass flow rate and induced wind velocity.These findings provide a theoretical foundation for the formulation of fire rescue strategies and emergency evacuation plans in inclined tunnels with one portal sealed.展开更多
Coal mine underground reservoir(CMUR) technology mitigates water scarcity in China's coal-rich western regions but lacks tailored solutions for steeply inclined coal seams.This study develops a novel framework of ...Coal mine underground reservoir(CMUR) technology mitigates water scarcity in China's coal-rich western regions but lacks tailored solutions for steeply inclined coal seams.This study develops a novel framework of steeply inclined coal mine underground reservoirs(SICMUR),which is a paradigm shift from conventional CMUR that the coal seam itself serves as the reservoir floor,challenging conventional designs due to depth-dependent permeability and mechanical constraints.Triaxial mechanical-seepage tests on Xinjiang Wudong coal samples(100,200,300 m depths) revealed a 3.5 MPa triaxial strength increase per 100 m depth and a 58-fold post-peak permeability surge at 300 versus 100 m.Similar model simulations revealed mining-induced stress redistribution and significant deformation effects,particularly subsidence and water-conducting fractures during lower coal seam mining.Results indicate a minimum 40 m safety distance between reservoirs and lower coal seams.Critical construction parameters were investigated for Wudong mine SICMUR as collapse zone heights(9.9–12.31 m) and waterconducting fracture zone heights(31.96–37.40 m).This work systematically bridges SICMUR concepts to field implementation,offering a framework for water preservation in steeply inclined mining while addressing safety concerns,providing a new approach for water reservation in steeply inclined coal mining.展开更多
This study focuses on steeply inclined and extremely thick coal seams(SIETCS)characterized by immense thickness,a steep inclination of coal seams(87°),and high horizontal stress.The geological conditions and mini...This study focuses on steeply inclined and extremely thick coal seams(SIETCS)characterized by immense thickness,a steep inclination of coal seams(87°),and high horizontal stress.The geological conditions and mining technology associated with SIETCS differ significantly from those of generally inclined coal seams,resulting in notable variations in roadway stress distributions.On SIETCS have predominantly examined the impact of rock layers flanking coal seams on rock bursts,with limited emphasis on SIETCS roadways.This study employs comprehensive methods,integrating numerical simulations,theoretical analyses,and field detections to investigate the stress distribution of SIETCS and the mechanisms of rock burst-induced vertical damage,subsequently validated in situ.The vertical stress in SIETCS is minimal,while horizontal stress is concentrated,leading to the formation of layered crack structures(LCS)that distribute above and below the roadways.Additionally,elastic energy significantly concentrates within the LCS.Axial dynamic compressive stress and vertical dynamic tensile stress along the LCS diminish its stability,readily triggering failure.During the LCS failure process,the stored energy is released,converting into kinetic energy required for coal body ejection after reaching the minimum energy for failure and dissipative energy,ultimately leading to rock burst-induced vertical damage in roadways.On-site detection and analysis within SIETCS,along with historical rock burst data,confirm the existence of LCS and its role in inducing vertical rock burst damage.This research establishes essential foundations for preventing rock bursts within SIETCS.展开更多
This research explores the characteristics of boiling in inclined pipes,a domain of great importance in engineering.Employing an experimental visualization technique,the boiling dynamics of deionizedwater are examined...This research explores the characteristics of boiling in inclined pipes,a domain of great importance in engineering.Employing an experimental visualization technique,the boiling dynamics of deionizedwater are examined at varying inclination angles,paying special attention to the emerging flow patterns.The findings demonstrate that the inclination angle significantly impacts flow pattern transitions within the 0°to 90°range.As the heat flux rises,bubbles form in the liquid.The liquid’s inertia extends the bubble-wall contact time,thereby delaying the onset of bulk bubble flow.Beyond a 90°inclination,however,the patterning behavior is more influenced by the fluid velocity.At low speeds,incomplete pipe filling results in a large liquid plug hindering flow,while high speeds lead to full pipe filling.In general,gravity,inertia,buoyancy forces,and capillary forces are themain influential factors in the considered problem.However,an analysis of the heat transfer coefficient and boiling curve for different inclination angles reveals that the observed variations are essentially due to corresponding changes in the flow pattern.Finally,an optimal mass flux and inclination angle,able to minimize total entropy generation and improve heat transfer efficiency,are determined by means of an entropy generation analysis.展开更多
A genuine neurotic condition is experienced when some blood constituents accumulate on the wall of the artery get withdrew from the wall, again join the circulatory system and coagulation occur. Role of copper nanopar...A genuine neurotic condition is experienced when some blood constituents accumulate on the wall of the artery get withdrew from the wall, again join the circulatory system and coagulation occur. Role of copper nanoparticles and inclined magnetic field on the peristaltic flow of a nanofluid in an annular region of inclined annulus is investigated.We represent the clot model by considering the small artery as an annulus whose outer tube has a wave of sinusoidal nature and inner tube has a clot on its walls. Lubrication approach is used to simplify the problem. Close form solutions are determined for temperature and velocity profile. Impact of related parameters on pressure rise, pressure gradient,velocity and streamlines are interpreted graphically. Comparison among the pure blood and copper blood is presented and analyzed. One main finding of the considered analysis is that the inclusion of copper nanoparticles enlarges the amplitude of the velocity. Therefore, the considered study plays a dominant role in biomedical applications.展开更多
The intention of this investigation is to study the effects of heat transfer and inclined magnetic field on the peristaltic flow of Williamson fluid in an asymmetric channel through porous medium. The governing two-di...The intention of this investigation is to study the effects of heat transfer and inclined magnetic field on the peristaltic flow of Williamson fluid in an asymmetric channel through porous medium. The governing two-dimensional equations are simplified under the assumption of long wavelength approximation. The simplified equations are solved for the stream function, temperature, and axial pressure gradient by using a regular perturbation method. The expression for pressure rise is computed numerically. The profiles of velocity, pressure gradient, temperature, heat transfer coefficient and stream function are sketched and interpreted for various embedded parameters and also the behavior of stream function for various wave forms is discussed through graphs. It is observed that the peristaltic velocity increases from porous medium to non-porous medium, the magnetic effects have increasing effect on the temperature, and the size of the trapped bolus decreases with the increasing of magnetic effects while the trend is reversed with the increasing of Darcy number. Moreover, limiting solutions of our problem are in close agreement with the corresponding results of the Newtonian fluid model.展开更多
The geological conditions of the Pingdingshan coal mining group were used to construct a physical model used to study the distribution and evolution of mining induced cracks in the overburden strata.Digital graphics t...The geological conditions of the Pingdingshan coal mining group were used to construct a physical model used to study the distribution and evolution of mining induced cracks in the overburden strata.Digital graphics technology and fractal theory are introduced to characterize the distribution and growth of the mining induced fractures in the overburden strata of an inclined coal seam.A relationship between fractal dimension of the fracture network and the pressure in the overburden strata is suggested.Mining induced fractures spread dynamically to the mining face and up into the roof as the length of advance increases.Moreover,the fractal dimension of the fracture network increases with increased mining length,in general,but decreases during a period from overburden strata separation until the main roof collapses.It is a1so shown that overburden strata pressure plays an important role in the evolution of mining induced fractures and that the fractal dimension of the fractures increases with the pressure of the overburden.展开更多
Based on the functional theory, catastrophe theory, simultaneity principle and the idea of strength reduction method （SRM）, the bearing capacity functional anti SRM of pile group foundation were established, and the...Based on the functional theory, catastrophe theory, simultaneity principle and the idea of strength reduction method （SRM）, the bearing capacity functional anti SRM of pile group foundation were established, and the criteria of ultimate load and the concept of safety storage coefficient （Css） were advanced. The inclined ultimate loads by the static loading test, load increment method （LIM） and SRM are compared. Theoretically, the ultimate load of piles does not change with the loading levels when it is calculated by SRM. When the one strength reduction parameter is applied in the calculation boundary, there are calculating errors because the bearing capacity action of soils happened in the finite zone. The inclined 10adings are 108, 132 and 144 kN, and SSC are 1.07, 0.94 and 0.79, respectively, so the calculation values of ultimate loads are about 115.56, 124.08 and 113.76 kN, respectively. The error between calculations and observation values is less than 6%. But .the error between calculations of LIM and observations is 20%. Because of the effect of inclined loading, the push-rotation phenomenon of screw pile group appears. Under this testing, the ultimate bearing capacity of piles is mostly determined by the horizontal ultimate bearing capacity, and the effect of the vertical component of inclined load should also be considered.展开更多
Prediction of surface subsidence caused by longwall mining operation in inclined coal seams is often very challenging. The existing empirical prediction methods are inflexible for varying geological and mining conditi...Prediction of surface subsidence caused by longwall mining operation in inclined coal seams is often very challenging. The existing empirical prediction methods are inflexible for varying geological and mining conditions. An improved influence function method has been developed to take the advantage of its fundamentally sound nature and flexibility. In developing this method, the original Knothe function has been transformed to produce a continuous and asymmetrical subsidence influence function. The empirical equations for final subsidence parameters derived from col- lected longwall subsidence data have been incorporated into the mathematical models to improve the prediction accuracy. A number of demonstration cases for longwall mining operations in coal seams with varying inclination angles, depths and panel widths have been used to verify the applicability of the new subsidence prediction model.展开更多
Numerical simulations of flow and heat transfer to supercritical RP-3 through the inclined tubes have been performed using LS k–e model embedded in Fluent. The physical properties of RP-3 were obtained using the gene...Numerical simulations of flow and heat transfer to supercritical RP-3 through the inclined tubes have been performed using LS k–e model embedded in Fluent. The physical properties of RP-3 were obtained using the generalized corresponding state laws based on the fourcomponent surrogate model. Mass flow rate is 0.3 g/s, system pressure is 3 MPa, inlet temperature is 373 K. Inclination of the inclined pipe varied from -90° to 90°, with heat flux varied from 300 k W/m^2 to 400 kW/m^2. Comparison between the calculated result and the experimental data indicates the range of error reasonable. The results of ±45° show that temperature inhomogeneity in inclined pipe produce the secondary flow in its cross section due to the buoyancy force. Depending on the strength of the temperature inhomogeneity, there will be two different forms of secondary flow and both contribute to the convective heat transfer in the pipe. The secondary flow intensity decreases when the inhomogeneity alleviates and thermal acceleration will play a leading role. It will have a greater impact on the turbulent flow to affect the convective heat transfer in the pipe. When changing the inclination, it affects the magnitude of the buoyant component in flow direction. The angle increases, the buoyancy component decreases. And the peak temperature of wall dominated by the secondary flow will move forward and increase in height.展开更多
The distribution of the final surface subsidence basin induced by longwall operations in inclined coal seam could be significantly different from that in flat coal seam and demands special prediction methods. Though m...The distribution of the final surface subsidence basin induced by longwall operations in inclined coal seam could be significantly different from that in flat coal seam and demands special prediction methods. Though many empirical prediction methods have been developed, these methods are inflexible for varying geological and mining conditions. An influence function method has been developed to take the advantage of its fundamentally sound nature and flexibility. In developing this method, significant modifications have been made to the original Knothe function to produce an asymmetrical influence function. The empirical equations for final subsidence parameters derived from US subsidence data and Chinese empirical values have been incorpo- rated into the mathematical models to improve the prediction accuracy. A corresponding computer program is developed. A number of subsidence cases for longwall mining operations in coal seams with varying inclination angles have been used to demonstrate the applicability of the developed subsidence prediction model.展开更多
The failure depth of the coal seam floor is one important consideration that must be kept in mind when mining is carried out above a confined aquifer.Determining the floor failure depth is the essential precondition f...The failure depth of the coal seam floor is one important consideration that must be kept in mind when mining is carried out above a confined aquifer.Determining the floor failure depth is the essential precondition for predicting the water-resisting ability of the floor.We have used a high-precision microseismic monitoring technique to overcome the limited amount of data available from field measurements. The failure depth of a coal seam floor,especially an inclined coal seam floor,may be more accurately estimated by monitoring the continuous,dynamic failure of the floor.The monitoring results indicate the failure depth of the coal seam floor near the workface conveyance roadway（the lower crossheading） is deeper and that the failure range is wider here compared to the coal seam floor near the return airway（the upper crossheading）.The results of micro-seismic monitoring show that the dangerous area for water-inrush from the coal seam floor may be identified.This provides an important field measurement that helps ensure safe and highly efficient mining of the inclined coal seam above the confined aquifer at the Taoyuan Coal Mine.展开更多
Engineering experience shows that outward dipping bedded rock slopes, especially including weak interlayers, are prone to slide under rainfall conditions. To investigate the effect of inclined weak interlayers at vari...Engineering experience shows that outward dipping bedded rock slopes, especially including weak interlayers, are prone to slide under rainfall conditions. To investigate the effect of inclined weak interlayers at various levels of depth below the surface on the variation of displacements and stresses in bedded rock slopes, four geo- mechanical model tests with artificial rainfall have been conducted. Displacements, water content as well as earth pressure in the model were monitored by means of various FBG (Fiber Bragg Grating) sensors. The results showed that the amount of displacement of a slope with a weak interlayer is 2.8 to 6.2 times larger than that of a slope without a weak interlayer during one rainfall event. Furthermore, the position of the weak interlayer in terms of depth below the surface has a significant effect on the zone of deformation in the model. In the slope with a high position weak interlayer, the recorded deformation was larger in the superficial layer of the model and smaller in the frontal portion than in the slope with a low position weak interlayer. The slope with two weak interlayers has the largest deformation at all locations of all test slopes. The slope without a weak interlayer was only saturated in its superficial layer, while the displacement decreased with depth. That was different from all slopes with a weak interlayer in which the largest displacement shifted from the superficial layer to the weak interlayer when rainfall persisted. Plastic deformation of the weak interlayer promoted the formation of cracks which caused more water to flow into the slope, thus causing larger deformation in the slope with weak interlayers. In addition, the slide thrust pressure showed a vibration phenomenon o.5 to 1 hour ahead of an abrupt increase of the deformation, which was interpreted as a predictor for rainfall-induced failure of bedded rock slopes.展开更多
基金supported by the National Natural Science Foundation of China(Nos.U2241240,12172045 and 12221002)the Opening Fund of State Key Laboratory of Explosion Science and Technology of Beijing Institute of Technology,China(No.ZDKT23-02)。
文摘Carbon Carbon(C/C)composites in thermal-protection system are exposed to severe thermochemical ablation and mechanical erosion,and their thermal-protection performance is of vital importance to the structural safety and flight status of hypersonic vehicles.We numerically analyzes the mesoscopic ablation-erosion of C/C Composites with Inclined Fibers(CCIF).First,a thermochemical ablation model describing the reaction-diffusion coupled problem of C/C composites on mesoscale is employed to analyze ablative process,and the corresponding surface ablation morphology is obtained.Then,the ablation morphology of CCIF is taken as the geometrical model for mechanical erosion analysis,and their damage and failure behavior under high-speed airflow shear is analyzed by using progressive damage method.Moreover,the effects of fiber inclined angle and airflow direction on the mechanical erosion of CCIF are investigated,and the ablationerosion behavior is analyzed and discussed.The results show that the failure modes of mechanical erosion in inner and edge regions are obviously different,showing granular and block erosion phenomena respectively.The mechanical erosion of CCIF in the direction of reverse flow is easier than that in the direction of forward flow.These results can provide a theoretical basis for the design and optimization of thermal protection system materials.
基金Science and Technology Major Project of Xinjiang Uygur Autonomous Region(2020A03003-7)Fundamental Research on Natural Science Program of Shaanxi Province(2021JM-180)+2 种基金Fundamental Research Funds for the Central Universities,CHD(Project for Leading Talents)(300102211302)Tianshan Cedar Plan of Science and Technology Department of Xinjiang Uygur Autonomous Region(2017XS13)Shaanxi Province Young Talent Lifting Program(CLGC202219).
文摘When the expressway crosses the goafs inevitably,the design is generally to build the road on coal pillars as much as possible.However,the existing coal pillars are often unable to meet relevant requirements of highway construction.Combining three-dimensional physical model tests,numerical simulations and field monitoring,with the Urumqi East Second Ring Road passing through acute inclined goafs as a background,the deformation and failure mechanism of the overlying rock and coal pillars in acute inclined goafs under expressway load were studied.And in accordance with construction requirements of subgrade,comprehensive consideration of the deformation and instability mechanism of acute inclined goafs,the treatment measures and suggestions for this type of geological disasters were put forward.The research results confirmed the rationality of coal pillars in acute inclined goafs under the expressway through grouting.According to the ratio of diff erent overlying rock thickness to coal pillar height,the change trend and value of the required grouting range were summarized,which can provide reference for similar projects.
文摘Magnetohydrodynamic(MHD)radiative chemically reactive mixed convection flow of a hybrid nanofluid(Al_(2)O_(3)–Cu/H_(2)O)across an inclined,porous,and stretched sheet is examined in this study,along with its unsteady heat and mass transport properties.The hybrid nanofluid’s enhanced heat transfer efficiency is a major benefit in high-performance engineering applications.It is composed of two separate nanoparticles suspended in a base fluid and is chosen for its improved thermal properties.Thermal radiation,chemical reactions,a transverse magnetic field,surface stretching with time,injection or suction through the porous medium,and the effect of inclination,which introduces gravity-induced buoyancy forces,are all important physical phenomena that are taken into account in the analysis.A system of nonlinear ordinary differential equations(ODEs)is derived from the governing partial differential equations for mass,momentum,and energy by applying suitable similarity transformations.This simplifies the modeling procedure.The bvp4c solver in MATLAB is then used to numerically solve these equations.Different governing parameters modify temperature,concentration,and velocity profiles in graphs and tables.These factors include radiation intensity,chemical reaction rate,magnetic field strength,unsteadiness,suction/injection velocity,inclination angle,and nanoparticle concentration.A complex relationship between buoyancy and magnetic factors makes hybrid nanofluids better at heat transmission than regular ones.Thermal systems including cooling technologies,thermal coatings,and electronic heat management benefit from these findings.
基金supported by the National Natural Science Foundation of China(Grant Nos.42277165,41920104007)the Hubei Natural Science Foundation(Grant No.2023AFD217).
文摘The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method.Field monitoring was conducted to assess the load and deformation of the initial support structure,and on-site investigations identified the distribution of cracked areas.In addition,numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure,which were then compared with field observations for validation.The variations in the lateral pressure coefficient and water pressure were evaluated.The results revealed that damage was primarily concentrated in the shoulder,spring line,and knee areas,with the bending moment at the knee increasing by up to 66.9%.The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support.Post-treatment analysis indicated significant reductions in axial force and bending moment,enhancing structural stability.These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulicpressure railroad tunnels.
基金Project(2021YFC2902101)supported by the National Key Research and Development Program of ChinaProjects(42271139,52174135)supported by the National Natural Science Foundation of China。
文摘The“upper coal and lower bauxite”resource distribution pattern is widespread in China,where mining of the overlying coal seam significantly alters the stress environment of the underlying bauxite layer.This study investigates the stability of inclined bauxite pillars under the influence of stress redistribution caused by coal seam extraction.A theoretical model is developed to calculate the direction and magnitude of principal stresses in the inclined floor strata,and a pillar stability analysis model is established that considers the effect of principal stress rotation.The research employs a combination of theoretical analysis,physical modeling,numerical simulation,and field observation.Findings indicate that stress rotation is most pronounced at both ends of the coal seam goaf,with the maximum clockwise and counterclockwise rotation angles of 19°and-40°,respectively,observed in the bauxite layer.Inclined bauxite pillars are subjected to combined compressive and shear loading.Under such conditions,clockwise rotation of principal stress increases the shear-to-normal stress ratio,thereby reducing pillar stability.Pillars located beneath the coal wall are the first to fail due to stress concentration and principal stress rotation,which can trigger a cascade of instability among the adjacent pillars.The findings provide a theoretical basis and practical guidance for ensuring the safe co-mining of coal seams and bauxite resources.
文摘In this paper,the authors examine various slip effects on themagnetic field and thermal radiative impacts on the flow,mass and heat transfer of a Jeffrey nanofluid over a 2-dimensional inclined stretching sheet by a porous media.The offered work is modelled to be in the form of a combination of coupled highly nonlinear partial differential equations in dimensional contexts.Governing equations were obtained,dimensionless parameters were defined in terms of similarity parameters,and the solutionswere obtained by the Homotopy Analysis Method(HAM).The analysis is significant as the effects of viscosity are identified and the important parameters are to be determined that could eventually control a type of flowbehaviour,especially in promoting the flowand inhibiting flowof velocity,temperature,and concentrations.The findings show that such an increase in themagnetic parameter decreases the velocity profile by approximately 15%due to more Lorentz forces,and thermal radiation increases the temperature profile by up to 25%,therefore,enhancing the rate of heat transfer.The process of Brownian motion and thermophoresis increases the depth of the thermal boundary layer by 10–20 percent and reduces in concentration profiles by 12 percent when the Brownian motion parameter increases.A velocity slip parameter lowers the velocity field by about 18 percent,and a parameter of permeability lowers the momentum of flow by another 10 percent.The HAM solutions show very high accuracy levels,having an order of convergence at level 15 and errormargins are well below 0.01 percent compared to the earlier studies.All these findings can provide profound knowledge in improving heat transmission in non-Newtonian fluid systems and can be used in biomedical engineering,thermal insulation,and industrial processes such as polymer extrusion and cooling technology.Principles of heat and mass transfer give us the crucial foundation on which to study the behavior of heat andmaterial flows in other engineering and scientific disciplines.Such principles apply to various fields of study,including the following engineering fields:mechanical,chemical,aerospace,civil,and environmental.
基金Projects(52278395,52208409) supported by the National Natural Science Foundation of ChinaProject(2022JJ40531) supported by the Natural Science Foundation of Hunan Province,China。
文摘Because of actual requirement,shield machine always excavates with an inclined angle in longitudinal direction.Since many previous studies mainly focus on the face stability of the horizontal shield tunnel,the effects of tensile strength cut-off and pore water pressure on the face stability of the longitudinally inclined shield tunnel are not well investigated.A failure mechanism of a longitudinally inclined shield tunnel face is constructed based on the spatial discretization technique and the tensile strength cut-off criterion is introduced to modify the constructed failure mechanism.The pore water pressure is introduced as an external force into the equation of virtual work and the objective function of the chamber pressure of the shield machine is obtained.Moreover,the critical chamber pressure of the longitudinally inclined shield tunnel is computed by optimal calculation.Parametric analysis indicates that both tensile strength cut-off and pore water pressure have a significant impact on the chamber pressure and the range of the collapse block.Finally,the theoretical results are compared with the numerical results calculated by FLAC3D software which proves that the proposed approach is effective.
基金financially supported by National Natural Science Foundation of China(NSFC)under Grant No.52208115Science and Technology Support Plan for Youth Innovation of Colleges and Universities of Shandong Province of Chain(No.2023KJ122)+2 种基金Leading Researcher Studio Fund of Jinan(No.202333050)Natural Science Foundation of Shandong Province(ZR2024ME027)Young Talent of Lifting engineering for Science and Technology in Shandong,China(SDAST2024QTA077).
文摘A sealed portal could significantly alter the flame shape and smoke flow characteristics in inclined tunnel fires.In inclined tunnels,two typical sealing conditions could be defined,namely the upper portal sealed and the lower portal sealed.In this study,the effects of tunnel slope on flame shape,flame length,along with smoke mass flow rate and induced velocity at the tunnel portal,are numerically investigated.The results show that,in all scenarios,flames initially rise vertically but tilt toward the sealed portal during the quasi-steady stage,with the largest tilt angle observed in tunnels sealed at the lower portal.The slope significantly affects the flame tilt angle.The flame tilt angle in tunnels with the lower portal sealed varies irregularly with the slope,while it decreases as the slope increases in tunnels with the upper portal sealed.Subsequently,the smoke mass flow rate and induced velocity at the tunnel portal are analyzed in detail.Drawing on the obtained data,the flame length prediction models for impinging flames and non-impinging flames under different sealing conditions are developed,along with dimensionless models for smoke mass flow rate and induced wind velocity.These findings provide a theoretical foundation for the formulation of fire rescue strategies and emergency evacuation plans in inclined tunnels with one portal sealed.
基金supported by Beijing Natural Science Foundation (No.8254049)the National Natural Science Foundation of China (No.52374139)the Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project (No.2024ZD1004505)。
文摘Coal mine underground reservoir(CMUR) technology mitigates water scarcity in China's coal-rich western regions but lacks tailored solutions for steeply inclined coal seams.This study develops a novel framework of steeply inclined coal mine underground reservoirs(SICMUR),which is a paradigm shift from conventional CMUR that the coal seam itself serves as the reservoir floor,challenging conventional designs due to depth-dependent permeability and mechanical constraints.Triaxial mechanical-seepage tests on Xinjiang Wudong coal samples(100,200,300 m depths) revealed a 3.5 MPa triaxial strength increase per 100 m depth and a 58-fold post-peak permeability surge at 300 versus 100 m.Similar model simulations revealed mining-induced stress redistribution and significant deformation effects,particularly subsidence and water-conducting fractures during lower coal seam mining.Results indicate a minimum 40 m safety distance between reservoirs and lower coal seams.Critical construction parameters were investigated for Wudong mine SICMUR as collapse zone heights(9.9–12.31 m) and waterconducting fracture zone heights(31.96–37.40 m).This work systematically bridges SICMUR concepts to field implementation,offering a framework for water preservation in steeply inclined mining while addressing safety concerns,providing a new approach for water reservation in steeply inclined coal mining.
基金support of the National Natural Science Foundation of China(52374180,52327804).
文摘This study focuses on steeply inclined and extremely thick coal seams(SIETCS)characterized by immense thickness,a steep inclination of coal seams(87°),and high horizontal stress.The geological conditions and mining technology associated with SIETCS differ significantly from those of generally inclined coal seams,resulting in notable variations in roadway stress distributions.On SIETCS have predominantly examined the impact of rock layers flanking coal seams on rock bursts,with limited emphasis on SIETCS roadways.This study employs comprehensive methods,integrating numerical simulations,theoretical analyses,and field detections to investigate the stress distribution of SIETCS and the mechanisms of rock burst-induced vertical damage,subsequently validated in situ.The vertical stress in SIETCS is minimal,while horizontal stress is concentrated,leading to the formation of layered crack structures(LCS)that distribute above and below the roadways.Additionally,elastic energy significantly concentrates within the LCS.Axial dynamic compressive stress and vertical dynamic tensile stress along the LCS diminish its stability,readily triggering failure.During the LCS failure process,the stored energy is released,converting into kinetic energy required for coal body ejection after reaching the minimum energy for failure and dissipative energy,ultimately leading to rock burst-induced vertical damage in roadways.On-site detection and analysis within SIETCS,along with historical rock burst data,confirm the existence of LCS and its role in inducing vertical rock burst damage.This research establishes essential foundations for preventing rock bursts within SIETCS.
基金supported by the National Natural Science Foundation of China(Project No.52166004)the National Key Research and Development Program of China(Project No.2022YFC3902000)the Major Science and Technology Special Project of Yunnan Province(Project Nos.202202AG050007,202202AG050002).
文摘This research explores the characteristics of boiling in inclined pipes,a domain of great importance in engineering.Employing an experimental visualization technique,the boiling dynamics of deionizedwater are examined at varying inclination angles,paying special attention to the emerging flow patterns.The findings demonstrate that the inclination angle significantly impacts flow pattern transitions within the 0°to 90°range.As the heat flux rises,bubbles form in the liquid.The liquid’s inertia extends the bubble-wall contact time,thereby delaying the onset of bulk bubble flow.Beyond a 90°inclination,however,the patterning behavior is more influenced by the fluid velocity.At low speeds,incomplete pipe filling results in a large liquid plug hindering flow,while high speeds lead to full pipe filling.In general,gravity,inertia,buoyancy forces,and capillary forces are themain influential factors in the considered problem.However,an analysis of the heat transfer coefficient and boiling curve for different inclination angles reveals that the observed variations are essentially due to corresponding changes in the flow pattern.Finally,an optimal mass flux and inclination angle,able to minimize total entropy generation and improve heat transfer efficiency,are determined by means of an entropy generation analysis.
文摘A genuine neurotic condition is experienced when some blood constituents accumulate on the wall of the artery get withdrew from the wall, again join the circulatory system and coagulation occur. Role of copper nanoparticles and inclined magnetic field on the peristaltic flow of a nanofluid in an annular region of inclined annulus is investigated.We represent the clot model by considering the small artery as an annulus whose outer tube has a wave of sinusoidal nature and inner tube has a clot on its walls. Lubrication approach is used to simplify the problem. Close form solutions are determined for temperature and velocity profile. Impact of related parameters on pressure rise, pressure gradient,velocity and streamlines are interpreted graphically. Comparison among the pure blood and copper blood is presented and analyzed. One main finding of the considered analysis is that the inclusion of copper nanoparticles enlarges the amplitude of the velocity. Therefore, the considered study plays a dominant role in biomedical applications.
文摘The intention of this investigation is to study the effects of heat transfer and inclined magnetic field on the peristaltic flow of Williamson fluid in an asymmetric channel through porous medium. The governing two-dimensional equations are simplified under the assumption of long wavelength approximation. The simplified equations are solved for the stream function, temperature, and axial pressure gradient by using a regular perturbation method. The expression for pressure rise is computed numerically. The profiles of velocity, pressure gradient, temperature, heat transfer coefficient and stream function are sketched and interpreted for various embedded parameters and also the behavior of stream function for various wave forms is discussed through graphs. It is observed that the peristaltic velocity increases from porous medium to non-porous medium, the magnetic effects have increasing effect on the temperature, and the size of the trapped bolus decreases with the increasing of magnetic effects while the trend is reversed with the increasing of Darcy number. Moreover, limiting solutions of our problem are in close agreement with the corresponding results of the Newtonian fluid model.
基金the financial support from the State Key Basic Research Program of China(No.2011CB201201)
文摘The geological conditions of the Pingdingshan coal mining group were used to construct a physical model used to study the distribution and evolution of mining induced cracks in the overburden strata.Digital graphics technology and fractal theory are introduced to characterize the distribution and growth of the mining induced fractures in the overburden strata of an inclined coal seam.A relationship between fractal dimension of the fracture network and the pressure in the overburden strata is suggested.Mining induced fractures spread dynamically to the mining face and up into the roof as the length of advance increases.Moreover,the fractal dimension of the fracture network increases with increased mining length,in general,but decreases during a period from overburden strata separation until the main roof collapses.It is a1so shown that overburden strata pressure plays an important role in the evolution of mining induced fractures and that the fractal dimension of the fractures increases with the pressure of the overburden.
基金Project(51178457) supported by the National Natural Science Foundation of ChinaProject(cstc2012jjys0001) supported by the Natural Science Foundation of Chongqing,ChinaProject(L2011231) supported by the Liaoning Education Department,China
文摘Based on the functional theory, catastrophe theory, simultaneity principle and the idea of strength reduction method （SRM）, the bearing capacity functional anti SRM of pile group foundation were established, and the criteria of ultimate load and the concept of safety storage coefficient （Css） were advanced. The inclined ultimate loads by the static loading test, load increment method （LIM） and SRM are compared. Theoretically, the ultimate load of piles does not change with the loading levels when it is calculated by SRM. When the one strength reduction parameter is applied in the calculation boundary, there are calculating errors because the bearing capacity action of soils happened in the finite zone. The inclined 10adings are 108, 132 and 144 kN, and SSC are 1.07, 0.94 and 0.79, respectively, so the calculation values of ultimate loads are about 115.56, 124.08 and 113.76 kN, respectively. The error between calculations and observation values is less than 6%. But .the error between calculations of LIM and observations is 20%. Because of the effect of inclined loading, the push-rotation phenomenon of screw pile group appears. Under this testing, the ultimate bearing capacity of piles is mostly determined by the horizontal ultimate bearing capacity, and the effect of the vertical component of inclined load should also be considered.
文摘Prediction of surface subsidence caused by longwall mining operation in inclined coal seams is often very challenging. The existing empirical prediction methods are inflexible for varying geological and mining conditions. An improved influence function method has been developed to take the advantage of its fundamentally sound nature and flexibility. In developing this method, the original Knothe function has been transformed to produce a continuous and asymmetrical subsidence influence function. The empirical equations for final subsidence parameters derived from col- lected longwall subsidence data have been incorporated into the mathematical models to improve the prediction accuracy. A number of demonstration cases for longwall mining operations in coal seams with varying inclination angles, depths and panel widths have been used to verify the applicability of the new subsidence prediction model.
基金funding support from National Natural Science Foundation of China (No. 51876005)
文摘Numerical simulations of flow and heat transfer to supercritical RP-3 through the inclined tubes have been performed using LS k–e model embedded in Fluent. The physical properties of RP-3 were obtained using the generalized corresponding state laws based on the fourcomponent surrogate model. Mass flow rate is 0.3 g/s, system pressure is 3 MPa, inlet temperature is 373 K. Inclination of the inclined pipe varied from -90° to 90°, with heat flux varied from 300 k W/m^2 to 400 kW/m^2. Comparison between the calculated result and the experimental data indicates the range of error reasonable. The results of ±45° show that temperature inhomogeneity in inclined pipe produce the secondary flow in its cross section due to the buoyancy force. Depending on the strength of the temperature inhomogeneity, there will be two different forms of secondary flow and both contribute to the convective heat transfer in the pipe. The secondary flow intensity decreases when the inhomogeneity alleviates and thermal acceleration will play a leading role. It will have a greater impact on the turbulent flow to affect the convective heat transfer in the pipe. When changing the inclination, it affects the magnitude of the buoyant component in flow direction. The angle increases, the buoyancy component decreases. And the peak temperature of wall dominated by the secondary flow will move forward and increase in height.
文摘The distribution of the final surface subsidence basin induced by longwall operations in inclined coal seam could be significantly different from that in flat coal seam and demands special prediction methods. Though many empirical prediction methods have been developed, these methods are inflexible for varying geological and mining conditions. An influence function method has been developed to take the advantage of its fundamentally sound nature and flexibility. In developing this method, significant modifications have been made to the original Knothe function to produce an asymmetrical influence function. The empirical equations for final subsidence parameters derived from US subsidence data and Chinese empirical values have been incorpo- rated into the mathematical models to improve the prediction accuracy. A corresponding computer program is developed. A number of subsidence cases for longwall mining operations in coal seams with varying inclination angles have been used to demonstrate the applicability of the developed subsidence prediction model.
基金supported by the National Basic Research Program ofChina(No.2010CB202210)the National Natural Science Foundation of China(No.50874103)+1 种基金the Natural Science Foundation of Jiangsu Province(No.KB2008135)as well as by the Qinglan Project of Jiangsu Province
文摘The failure depth of the coal seam floor is one important consideration that must be kept in mind when mining is carried out above a confined aquifer.Determining the floor failure depth is the essential precondition for predicting the water-resisting ability of the floor.We have used a high-precision microseismic monitoring technique to overcome the limited amount of data available from field measurements. The failure depth of a coal seam floor,especially an inclined coal seam floor,may be more accurately estimated by monitoring the continuous,dynamic failure of the floor.The monitoring results indicate the failure depth of the coal seam floor near the workface conveyance roadway（the lower crossheading） is deeper and that the failure range is wider here compared to the coal seam floor near the return airway（the upper crossheading）.The results of micro-seismic monitoring show that the dangerous area for water-inrush from the coal seam floor may be identified.This provides an important field measurement that helps ensure safe and highly efficient mining of the inclined coal seam above the confined aquifer at the Taoyuan Coal Mine.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41502299,41372306)Research Planning of Sichuan Education Department,China(Grant No.16ZB0105)
文摘Engineering experience shows that outward dipping bedded rock slopes, especially including weak interlayers, are prone to slide under rainfall conditions. To investigate the effect of inclined weak interlayers at various levels of depth below the surface on the variation of displacements and stresses in bedded rock slopes, four geo- mechanical model tests with artificial rainfall have been conducted. Displacements, water content as well as earth pressure in the model were monitored by means of various FBG (Fiber Bragg Grating) sensors. The results showed that the amount of displacement of a slope with a weak interlayer is 2.8 to 6.2 times larger than that of a slope without a weak interlayer during one rainfall event. Furthermore, the position of the weak interlayer in terms of depth below the surface has a significant effect on the zone of deformation in the model. In the slope with a high position weak interlayer, the recorded deformation was larger in the superficial layer of the model and smaller in the frontal portion than in the slope with a low position weak interlayer. The slope with two weak interlayers has the largest deformation at all locations of all test slopes. The slope without a weak interlayer was only saturated in its superficial layer, while the displacement decreased with depth. That was different from all slopes with a weak interlayer in which the largest displacement shifted from the superficial layer to the weak interlayer when rainfall persisted. Plastic deformation of the weak interlayer promoted the formation of cracks which caused more water to flow into the slope, thus causing larger deformation in the slope with weak interlayers. In addition, the slide thrust pressure showed a vibration phenomenon o.5 to 1 hour ahead of an abrupt increase of the deformation, which was interpreted as a predictor for rainfall-induced failure of bedded rock slopes.
