During the process of constructional backfill mining,the cemented paste backfill(CPB)typically exhibits a high degree of brittleness and limited resistance to failure.In this study,the mechanical and damage evolution ...During the process of constructional backfill mining,the cemented paste backfill(CPB)typically exhibits a high degree of brittleness and limited resistance to failure.In this study,the mechanical and damage evolution characteristics of waste tire steel fiber(WTSF)-modified CPB were studied through uniaxial compression tests,acoustic emission(AE)tests,and scanning electron microscopy(SEM).The results showed that the uniaxial compressive strength(UCS)decreased when the WTSF content was 0.5%,1%,and 1.5%.When the WTSF content reached 1%,the UCS of the modified CPB exhibited a minimal decrease(0.37 MPa)compared to that without WTSF.When the WTSF content was 0.5%,1%,and 1.5%,peak strain of the WTSF-modified CPB increased by 18%,31.33%,and 81.33%,while the elastic modulus decreased by 21.31%,26.21%,and 45.42%,respectively.The addition of WTSF enhances the activity of AE events in the modified CPB,resulting in a slower progression of the entire failure process.After the failure,the modified CPB retained a certain level of load-bearing capacity.Generally,the failure of the CPB was dominated by tensile cracks.After the addition of WTSF,a gradual increase in the proportion of tensile cracks was observed upon loading the modified CPB sample to the pore compaction stage.The three-dimensional localization of AE events showed that the WTSF-modified CPB underwent progressive damage during the loading,and the samples still showed good integrity after failure.Additionally,the response relationship between energy evolution and damage development of WTSF-modified CPB during uniaxial compression was analyzed,and the damage constitutive model of CPB samples with different WTSF contents was constructed.This study provides a theoretical basis for the enhancement of CPB modified by adding WTSF,serving as a valuable reference for the design of CPB constructional backfill.展开更多
A numerical method has been used to analyze the flow field related to a NACA 0015 airfoil with and without a flap and assess the influence of the flap height and angle on the surface pressure coefficient,lift coeffici...A numerical method has been used to analyze the flow field related to a NACA 0015 airfoil with and without a flap and assess the influence of the flap height and angle on the surface pressure coefficient,lift coefficient,and drag coefficient.The numerical results demonstrate that the flap can effectively improve the lift coefficient of the airfoil;however,at small attack angles,its influence is significantly reduced.When the angle of attack exceeds the critical stall angle and the flap height is 1.5%of the chord length,the influence of the flap becomes very evident.As the flap height increases,the starting point of the separation vortex gradually moves forward and generates a larger wake vortex.Optimal aerodynamic characteristics are obtained for 1.5%(of the chord length)flap height and a 45°flap angle;in this case,the separation vortex is effectively reduced.展开更多
To study the impact of the trailing-edge wear on the vibrational behavior of wind-turbine blades,unworn blades and trailing-edge worn blades have been assessed through relevant modal tests.According to these experimen...To study the impact of the trailing-edge wear on the vibrational behavior of wind-turbine blades,unworn blades and trailing-edge worn blades have been assessed through relevant modal tests.According to these experiments,the natural frequencies of trailing-edge worn blades-1,-2,and-3 increase the most in the second to fourth order,thefifth order increases in the middle,and thefirst order increases the least.The damping ratio data indi-cate that,in general,thefirstfive-order damping ratios of trailing-edge worn blades-1 and trailing-edge worn blades-2 are reduced,and thefirstfive-order damping ratios of trailing-edge worn blades-3 are slightly improved.The mode shape diagram shows that the trailing-edge worn blades-1 and-2 have a large swing in the tip and the blade,whereas the second-and third-order vibration shapes of the trailing edge-worn blade-3 tend to be improved.Overall,all these results reveal that the blade’s mass and the wear area are the main fac-tors affecting the vibration characteristics of wind turbine blades.展开更多
Integrated printing of magnetic soft robots with complex structures using recyclable materials to achieve sustainability of the soft robots remains a persistent challenge.Here,we propose a kind of ferromagnetic fibers...Integrated printing of magnetic soft robots with complex structures using recyclable materials to achieve sustainability of the soft robots remains a persistent challenge.Here,we propose a kind of ferromagnetic fibers that can be used to print soft robots with complex structures.These ferromagnetic fibers are recyclable and can make soft robots sustainable.The ferromagnetic fibers based on thermoplastic polyurethane(TPU)/NdFeB hybrid particles are extruded by an extruder.We use a desktop three-dimensional(3D)printer to demonstrate the feasibility of printing two-dimensional(2D)and complex 3D soft robots.These printed soft robots can be recycled and reprinted into new robots once their tasks are completed.Moreover,these robots show almost no difference in actuation capability compared to prior versions and have new functions.Successful applications include lifting,grasping,and moving objects,and these functions can be operated untethered wirelessly.In addition,the locomotion of the magnetic soft robot in a human stomach model shows the prospect of medical applications.Overall,these fully recyclable ferromagnetic fibers pave the way for printing and reprinting sustainable soft robots while also effectively reducing e-waste and robotics waste materials,which is important for resource conservation and environmental protection.展开更多
Coal-rock interface identification technology was pivotal in automatically adjusting the shearer's cutting drum during coal mining.However,it also served as a technical bottleneck hindering the advancement of inte...Coal-rock interface identification technology was pivotal in automatically adjusting the shearer's cutting drum during coal mining.However,it also served as a technical bottleneck hindering the advancement of intelligent coal mining.This study aimed to address the poor accuracy of current coal-rock identification technology on comprehensive working faces,coupled with the limited availability of coal-rock datasets.The loss function of the SegFormer model was enhanced,the model's hyperparameters and learning rate were adjusted,and an automatic recognition method was proposed for coal-rock interfaces based on FL-SegFormer.Additionally,an experimental platform was constructed to simulate the dusty environment during coal-rock cutting by the shearer,enabling the collection of coal-rock test image datasets.The morphology-based algorithms were employed to expand the coal-rock image datasets through image rotation,color dithering,and Gaussian noise injection so as to augment the diversity and applicability of the datasets.As a result,a coal-rock image dataset comprising 8424 samples was generated.The findings demonstrated that the FL-SegFormer model achieved a Mean Intersection over Union(MIoU)and mean pixel accuracy(MPA)of 97.72%and 98.83%,respectively.The FLSegFormer model outperformed other models in terms of recognition accuracy,as evidenced by an MloU exceeding 95.70% of the original image.Furthermore,the FL-SegFormer model using original coal-rock images was validated from No.15205 working face of the Yulin test mine in northern Shaanxi.The calculated average error was only 1.77%,and the model operated at a rate of 46.96 frames per second,meeting the practical application and deployment requirements in underground settings.These results provided a theoretical foundation for achieving automatic and efficient mining with coal mining machines and the intelligent development of coal mines.展开更多
Combustion noise takes large proportion in diesel engine noise and the studies of its influence factors play an important role in noise reduction. Engine noise and cylinder pressure measurement experiments were carrie...Combustion noise takes large proportion in diesel engine noise and the studies of its influence factors play an important role in noise reduction. Engine noise and cylinder pressure measurement experiments were carried out. And the improved attenuation curves were obtained, by which the engine noise was predicted. The effect of fuel injection parameters in combustion noise was investigated during the combustion process. At last, the method combining single variable optimization and multivariate combination was introduced to online optimize the combustion noise. The results show that injection parameters can affect the cylinder pressure rise rate and heat release rate, and consequently affect the cylinder pressure load and pressure oscillation to influence the combustion noise. Among these parameters, main injection advance angle has the greatest influence on the combustion noise, while the pilot injection interval time takes the second place, and the pilot injection quantity is of minimal impact. After the optimal design of the combustion noise, the average sound pressure level of the engine is distinctly reduced by 1.0 d B(A) generally. Meanwhile, the power, emission and economy performances are ensured.展开更多
Valves are widely used in various working conditions for their flow control functions,and the cavitation inside valves has been investigated owing to its harm to the valve itself and the connecting downstream parts.Th...Valves are widely used in various working conditions for their flow control functions,and the cavitation inside valves has been investigated owing to its harm to the valve itself and the connecting downstream parts.This paper presents a comprehensive review of the progress that has been achieved in the past years about cavitation in valves including both mechanical heart valves and control valves.The review is divided in the following parts,namely the location where there is a high possibility of the occurrence of cavitation,the parameters that affect cavitation intensity,and the methods to minimize cavitation intensity.It should be noticed that although simulation has been widely used,advanced experiments are still needed in order to obtain accurate analysis of cavitation in valves and the cavitation model still needs to be improved.展开更多
For a deeper understanding of the deformation failure behavior of jointed rock, numerical compression simulations are carried out on a rock specimen containing non-persistent joints under confining pressure with the b...For a deeper understanding of the deformation failure behavior of jointed rock, numerical compression simulations are carried out on a rock specimen containing non-persistent joints under confining pressure with the bondedparticle model. The microscopic parameters which can reflect the macroscopic mechanical properties and failure behavior of artificial jointed specimens are firstly calibrated. Then, the influence of joint inclination and confining pressure on stress-strain curves, crack patterns, and contact force distributions of jointed rock are investigated. The simulation results show that both the compressive strength and elastic modulus of the specimens increase with increasing confining pressure, and these two mechanical parameters decrease first and then increase with the increase of joints inclination. The sensitivity of strength and elastic modulus to confining pressure is not the same in different joints inclinations, which has the least impact on specimens with α=90°. Under low confining pressure, the failure modes are controlled by the joint inclination. As the confining pressure increased, the initiation and propagation of tensile crack are gradually inhibited, and the failure mode is transferred from tensile failure to shear-compression failure. Finally, the reinforcement effect of prestressed bolt support on engineering fractured rock mass is discussed.展开更多
The influence of multipass high rotating speed friction stir processing(FSP)on the microstructure evolution,corrosion behavior,and tensile properties of the stirred zone(SZ)was investigated by EBSD,TEM,SEM,electrochem...The influence of multipass high rotating speed friction stir processing(FSP)on the microstructure evolution,corrosion behavior,and tensile properties of the stirred zone(SZ)was investigated by EBSD,TEM,SEM,electrochemical workstation and electronic universal testing machine.The mean grain size of the SZ is significantly refined,and it increases with the increase of the processing pass.In addition to an obvious increase in the number,the distribution ofβ-Al12Mg17 precipitates also becomes more uniform and dispersed with increasing the processing pass.Compared with the as-received AZ31 alloy,the tensile properties of the SZ are hardly improved,but the corrosion resistances are significantly enhanced.The corrosion potential of the SZ prepared by 4-pass FSP is increased from−1.56 V for the unprocessed AZ31 alloy to−1.19 V,while the corrosion current is decreased from 1.55×10^−4 to 5.47×10^−5 A.展开更多
Many natural fibers are lightweight and display remarkable strength and toughness.These properties originate from the fibers’hierarchical structures,assembled from the molecular to macroscopic scale.The natural spinn...Many natural fibers are lightweight and display remarkable strength and toughness.These properties originate from the fibers’hierarchical structures,assembled from the molecular to macroscopic scale.The natural spinning systems that produce such fibers are highly energy efficient,inspiring researchers to mimic these processes to realize robust artificial spinning.Significant developments have been achieved in recent years toward the preparation of high-performance bio-based fibers.Beyond excellent mechanical properties,bio-based fibers can be functionalized with a series of new features,thus expanding their sophisticated applications in smart textiles,electronic sensors,and biomedical engineering.Here,recent progress in the construction of bio-based fibers is outlined.Various bioinspired spinning methods,strengthening strategies for mechanically strong fibers,and the diverse applications of these fibers are discussed.Moreover,challenges in reproducing the mechanical performance of natural systems and understanding their dynamic spinning process are presented.Finally,a perspective on the development of biological fibers is given.展开更多
The gasification kinetic modelling of two Victorian brown coal(Yallourn and Maddingley)chars and the validity for entrained flow gasification were investigated in this study.The study was conducted in a thermogravimet...The gasification kinetic modelling of two Victorian brown coal(Yallourn and Maddingley)chars and the validity for entrained flow gasification were investigated in this study.The study was conducted in a thermogravimetric analyzer(TGA)at 750–1100℃,30%–90%CO_(2)concentration using different char particle sizes within 20–106 mm.It was found that random pore model and modified volumetric model are applicable for TGA results,but volumetric model and grain model are not.The effect of particle size under106 mm on gasification rate is very limited.Activation energies of Maddingley char and Yallourn char in CO_(2)gasification are 219–220 and 197–208 k J/mol,respectively.The pre-exponential factors are in the same order of magnitude,and they increased as particle size decreased.A mathematical model was developed to predict carbon conversion over time for entrained flow gasification of Victorian brown coal chars at 1000–1400℃.展开更多
Photothermal membrane distillation(MD)is a promising technology for desalination and water purification.However,solar-thermal conversion suffers from low energy efficiency(a typical solar-water efficiency of ~50%),whi...Photothermal membrane distillation(MD)is a promising technology for desalination and water purification.However,solar-thermal conversion suffers from low energy efficiency(a typical solar-water efficiency of ~50%),while complex modifications are needed to reduce membrane fouling.Here,we demonstrate a new concept of solar vapour gap membrane distillation(SVGMD)synergistically combining self-guided water transport,localized heating,and separation of membrane from feed solution.A free-standing,multifunctional light absorber based on graphene array is custom-designed to locally heat the thin water layer transporting through graphene nanochannels.The as-generated vapour passes through a gap and condenses,while salt/contaminants are rejected before reaching the membrane.The high solar-water efficiency(73.4% at 1 sun),clean water collection ratio(82.3%),excellent anti-fouling performance,and stable permeate flux in continuous operation over 72 h are simultaneously achieved.Meanwhile,SVGMD inherits the advantage of MD in microorganism removal and water collection,enabling the solar-water efficiency 3.5 times higher compared to state-of-the-art solar vapour systems.A scaled system to treat oil/seawater mixtures under natural sunlight is developed with a purified water yield of 92.8 kg m-2 day-1.Our results can be applied for diverse mixed-phase feeds,leading to the next-generation solar-driven MD technology.展开更多
Double-suction centrifugal pumps have been applied extensively in many areas,and the significance of pressure fluctuations inside these pumps with large power is becoming increasingly important.In this study,a double-...Double-suction centrifugal pumps have been applied extensively in many areas,and the significance of pressure fluctuations inside these pumps with large power is becoming increasingly important.In this study,a double-suction centrifugal pump with a high-demand for vibration and noise was redesigned by increasing the flow uniformity at the impeller discharge,implemented by combinations of more than two parameters.First,increasing the number of the impeller blades was intended to enhance the bounding effect that the blades imposed on the fluid.Subsequently,increasing the radial gap between the impeller and volute was applied to reduce the rotor-stator interaction.Finally,the staggered arrangement was optimized to weaken the efficacy of the interference superposition.Based on numerical simulation,the steady and unsteady characteristics of the pump models were calculated.From the fluctuation analysis in the frequency domain,the dimensionless pressure fluctuation amplitude at the blade passing frequency and its harmonics,located on the monitoring points in the redesigned pumps(both with larger radial gap),are reduced a lot.Further,in the volute of the model with new impellers staggered at 12°,the average value for the dimensionless pressure fluctuation amplitude decreases to 6%of that in prototype pump.The dimensionless rootmean-square pressure contour on the mid-span of the impeller tends to be more uniform in the redesigned models(both with larger radial gap);similarly,the pressure contour on the mid-section of the volute presents good uniformity in these models,which in turn demonstrating a reduction in the pressure fluctuation intensity.The results reveal the mechanism of pressure fluctuation reduction in a double-suction centrifugal pump,and the results of this study could provide a reference for pressure fluctuation reduction and vibration performance reinforcement of doublesuction centrifugal pumps and other pumps.展开更多
Electric double-layer capacitors(EDLCs) are advanced electrochemical devices for energy storage and have attracted strong interest due to their outstanding properties. Rational optimization of electrode–electrolyte i...Electric double-layer capacitors(EDLCs) are advanced electrochemical devices for energy storage and have attracted strong interest due to their outstanding properties. Rational optimization of electrode–electrolyte interactions is of vital importance to enhance device performance for practical applications. Molecular dynamics(MD) simulations could provide theoretical guidelines for the optimal design of electrodes and the improvement of capacitive performances, e.g., energy density and power density. Here we discuss recent MD simulation studies on energy storage performance of electrode materials containing porous to nanostructures. The energy storage properties are related to the electrode structures, including electrode geometry and electrode modifications. Altering electrode geometry, i.e., pore size and surface topography,can influence EDL capacitance. We critically examine different types of electrode modifications, such as altering the arrangement of carbon atoms, doping heteroatoms and defects, which can change the quantum capacitance. The enhancement of power density can be achieved by the intensified ion dynamics and shortened ion pathway.Rational control of the electrode morphology helps improve the ion dynamics by decreasing the ion diffusion pathway. Tuning the surface properties(e.g., the affinity between the electrode and the ions) can affect the ionpacking phenomena. Our critical analysis helps enhance the energy and power densities of EDLCs by modulating the corresponding electrode structures and surface properties.展开更多
In this work, a novel direct current （DC） atmospheric pressure rotating gliding arc （RGA） plasma reactor has been developed for plasma-assisted chemical reactions. The influence of the gas composition and the gas ...In this work, a novel direct current （DC） atmospheric pressure rotating gliding arc （RGA） plasma reactor has been developed for plasma-assisted chemical reactions. The influence of the gas composition and the gas flow rate on the arc dynamic behaviour and the formation of reactive species in the N2 and air gliding arc plasmas has been investigated by means of electrical signals, high speed photography, and optical emission spectroscopic diagnostics. Compared to conventional gliding arc reactors with knife-shaped electrodes which generally require a high flow rate （e.g., 10-20 L/min） to maintain a long arc length and reasonable plasma discharge zone, in this RGA system, a lower gas flow rate （e.g., 2 L/min） can also generate a larger effective plasma reaction zone with a longer arc length for chemical reactions. Two different motion patterns can be clearly observed in the N2 and air RGA plasmas. The time-resolved arc voltage signals show that three different arc dynamic modes, the arc restrike mode, takeover mode, and combined modes, can be clearly identified in the RGA plasmas. The occurrence of different motion and arc dynamic modes is strongly dependent on the composition of the working gas and gas flow rate.展开更多
Soft rock squeezing deformation mainly consists of pre-peak damage-dilatancy and post-peak fracture-bulking at the excavation unloading instant,and creep-dilatancy caused by time-dependent damage and fracturing.Based ...Soft rock squeezing deformation mainly consists of pre-peak damage-dilatancy and post-peak fracture-bulking at the excavation unloading instant,and creep-dilatancy caused by time-dependent damage and fracturing.Based on the classic elastoplastic and Perzyna over-stress viscoplastic theories,as well as triaxial unloading confining pressure test and triaxial unloading creep test results,an elastoplastic and viscoplastic damage constitutive model is established for the short-and long-term dilatancy and fracturing behavior of soft rock squeezing deformation.Firstly,the criteria for each deformation and failure stage are expressed as a linear function of confining pressure.Secondly,the total damage evolution equation considering time-dependent damage is proposed,including the initial damage produced at the excavation instant,in which the damage variable increases exponentially with the lateral strain,and creep damage.Thirdly,a transient five-stages elasto-plastic constitutive equation for the short-term deformation after excavation that comprised of elasticity,pre-peak damage-dilatancy,post-peak brittle-drop,linear strain-softening,and residual perfectly-plastic regimes is developed based on incremental elasto-plastic theory and the nonassociated flow rule.Fourthly,regarding the timedependent properties of soft rock,based on the Perzyna viscoplastic over-stress theory,a viscoplastic damage model is set up to capture creep damage and dilatancy behavior.Viscoplastic strain is produced when the stress exceeds the initial static yield surface fs;the distance between the static yield surface fs and the dynamic yield surface fd determines the viscoplastic strain rate.Finally,the established constitutive model is numerically implemented and field applied to the-848 m belt conveyer haulage roadway of Huainan Panyidong Coal Mine.Laboratory test results and in-situ monitoring results validate the rationality of the established constitutive model.The presented model takes both the transient and time-dependent damage and fracturing into consideration.展开更多
A coaxial mixer consisting of an anchor and a Rushton turbine was selected as the research object,whose solid suspension characteristics were studied with the help of Computational Fluid Dynamics(CFD)method.Based on t...A coaxial mixer consisting of an anchor and a Rushton turbine was selected as the research object,whose solid suspension characteristics were studied with the help of Computational Fluid Dynamics(CFD)method.Based on the Eulerian–Eulerian method and modified Brucato drag model,the just-suspension speed of impeller was predicted,and the simulation results were in good agreement with the experimental data.The quality of solid suspension under different rotation modes was also compared,and the results showed the coaxial mixer operating under co-rotation mode could get the best performance,and a larger anchor speed was beneficial to solid suspension by enhancing the turbulent intensity at the bottom.Compared with the anchor,the inner Rushton turbine played a dominant role in solid suspension due to its high rotational speed,whereas an extremely high inner impeller speed would make the uniformity of solid distributions become worse.Additionally,the effects of solid phase properties were also investigated,the results revealed that the higher the overall solid volume fraction and the smaller the Shields number,the worse the performance of solid suspension,meanwhile the solid suspension was more susceptible to solid density compared with particle diameter within the same Shields number gradient.展开更多
Polymer-derived ceramic(PDC) thin films are promising wear-resistant coatings for protecting metals and carbon-carbon composites from corrosion and oxidation.However,the high pyrolysis temperature hinders the applicat...Polymer-derived ceramic(PDC) thin films are promising wear-resistant coatings for protecting metals and carbon-carbon composites from corrosion and oxidation.However,the high pyrolysis temperature hinders the applications on substrate materials with low melting points.We report a new synthesis route for PDC coatings using initiated chemical vapor deposited poly(1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane)(pV_3D_3) as the precurs or.We investigated the changes in siloxane moieties and the network topology,and proposed a three-stage mechanism for the thermal annealing process.The rise of the connectivity number for the structures obtained at increased annealing temperatures was found with strong correlation to the enhanced mechanical properties and thermal conductivity.Our PDC films obtained via annealing at 850℃ exhibit at least 14.6% higher hardness than prior reports for PDCs synthesized below 1100℃.Furthermore,thermal conductivity up to 1.02 W(mK)^(-1) was achieved at the annealing temperature as low as 700℃,which is on the same order of magnitude as PDCs obtained above 1100℃.Using minimum thermal conductivity models,we found that the thermal transport is dominated by diffusons in the films below the percolation of rigidity,while ultra-short mean-free path phonons contribute to the thermal conductivity of the films above the percolation threshold.The findings of this work provide new insights for the development of wear-resistant and thermally conductive PDC thin films for durable protection coatings.展开更多
A mathematical model was developed to predict the maximum heat transfer capacity of high temperature heat pipe with triangular grooved wick. The effects of the inclination angle and geometry structure were considered ...A mathematical model was developed to predict the maximum heat transfer capacity of high temperature heat pipe with triangular grooved wick. The effects of the inclination angle and geometry structure were considered in the proposed model.Maximum heat transfer capacity was also investigated experimentally. The model was validated by comparing with the experimental results. The maximum heat transfer capacity increases with the vapor core radius increasing. Compared with the inclination angle of0°, the maximum heat transfer capacity increases at the larger inclination angle, and the change with temperature is larger. The performance of heat pipe with triangular grooved wick is greatly influenced by gravity, so it is not recommended to be applied to the dish solar heat pipe receiver.展开更多
Horizontal section top-coal(HSTCC)caving offers a powerful method to efficiently excavate rude coal in steep and thick seams,and pre-blasting weakening has a profound effect on pursuing great production,high efficienc...Horizontal section top-coal(HSTCC)caving offers a powerful method to efficiently excavate rude coal in steep and thick seams,and pre-blasting weakening has a profound effect on pursuing great production,high efficiency and good benefit under particular conditions like a small-scale working face with large-scale sectional caving height.+564-level HSTCC working face in B3–6coal seams of Jiangou Colliery in Urumqi was taken as study case for in situ industrial experiment.Total thickness of seams in the study case is about 50.0 m and average angel here is over 83°.In the industrial experiments,at first we adopted continuous charge machine and emulsion matrix explosive to substitute for traditional blasting schemes for specific geological settings in the study case.Hybrid analyses and assessments with blasting crack propagation analysis,abutment pressure monitoring prediction and economical benefit assessment were attributed to be able to attest pre-blasting weakening effects practically.Meanwhile crack propagation analysis after pre-blasting weakening showed that in all triple monitoring bore holes rock masses of top-coal would be fallen into three stages from the bottom up:fracture zone,plastic zone and elastic zone generally,and fracture toughness respectively in correspondent zones was calculated by the analytical formula:0.5616–0.8806,0.6403–0.9541 and0.7535–1.1900 MPa m1/2after pre-blasting weakening.Pressure monitoring prediction and economical benefit assessment also indicated that it was necessary to introduce the pre-blasting weakening with predominant blasting scheme from both views.For excavation in extremely steep and thick coal seams,relevant results would be a useful tool to study the mechanism of pre-blasting weakening both qualitatively and quantitatively.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52274143 and 51874284).
文摘During the process of constructional backfill mining,the cemented paste backfill(CPB)typically exhibits a high degree of brittleness and limited resistance to failure.In this study,the mechanical and damage evolution characteristics of waste tire steel fiber(WTSF)-modified CPB were studied through uniaxial compression tests,acoustic emission(AE)tests,and scanning electron microscopy(SEM).The results showed that the uniaxial compressive strength(UCS)decreased when the WTSF content was 0.5%,1%,and 1.5%.When the WTSF content reached 1%,the UCS of the modified CPB exhibited a minimal decrease(0.37 MPa)compared to that without WTSF.When the WTSF content was 0.5%,1%,and 1.5%,peak strain of the WTSF-modified CPB increased by 18%,31.33%,and 81.33%,while the elastic modulus decreased by 21.31%,26.21%,and 45.42%,respectively.The addition of WTSF enhances the activity of AE events in the modified CPB,resulting in a slower progression of the entire failure process.After the failure,the modified CPB retained a certain level of load-bearing capacity.Generally,the failure of the CPB was dominated by tensile cracks.After the addition of WTSF,a gradual increase in the proportion of tensile cracks was observed upon loading the modified CPB sample to the pore compaction stage.The three-dimensional localization of AE events showed that the WTSF-modified CPB underwent progressive damage during the loading,and the samples still showed good integrity after failure.Additionally,the response relationship between energy evolution and damage development of WTSF-modified CPB during uniaxial compression was analyzed,and the damage constitutive model of CPB samples with different WTSF contents was constructed.This study provides a theoretical basis for the enhancement of CPB modified by adding WTSF,serving as a valuable reference for the design of CPB constructional backfill.
基金supported by the National Natural Science Foundation Project(Grant Numbers 51966018 and 51466015)the Key Research&Development Program of Xinjiang(Grant Number 2022B01003).
文摘A numerical method has been used to analyze the flow field related to a NACA 0015 airfoil with and without a flap and assess the influence of the flap height and angle on the surface pressure coefficient,lift coefficient,and drag coefficient.The numerical results demonstrate that the flap can effectively improve the lift coefficient of the airfoil;however,at small attack angles,its influence is significantly reduced.When the angle of attack exceeds the critical stall angle and the flap height is 1.5%of the chord length,the influence of the flap becomes very evident.As the flap height increases,the starting point of the separation vortex gradually moves forward and generates a larger wake vortex.Optimal aerodynamic characteristics are obtained for 1.5%(of the chord length)flap height and a 45°flap angle;in this case,the separation vortex is effectively reduced.
基金supported by the National Natural Science Foundation Project(Nos.51966018 and 51466015)the Key Research&Development Program of Xinjiang(Grant No.2022B01003).
文摘To study the impact of the trailing-edge wear on the vibrational behavior of wind-turbine blades,unworn blades and trailing-edge worn blades have been assessed through relevant modal tests.According to these experiments,the natural frequencies of trailing-edge worn blades-1,-2,and-3 increase the most in the second to fourth order,thefifth order increases in the middle,and thefirst order increases the least.The damping ratio data indi-cate that,in general,thefirstfive-order damping ratios of trailing-edge worn blades-1 and trailing-edge worn blades-2 are reduced,and thefirstfive-order damping ratios of trailing-edge worn blades-3 are slightly improved.The mode shape diagram shows that the trailing-edge worn blades-1 and-2 have a large swing in the tip and the blade,whereas the second-and third-order vibration shapes of the trailing edge-worn blade-3 tend to be improved.Overall,all these results reveal that the blade’s mass and the wear area are the main fac-tors affecting the vibration characteristics of wind turbine blades.
基金funded by the International Cooperation Program of the Natural Science Foundation of China(No.52261135542)Zhejiang Provincial Natural Science Foundation of China(No.LD22E050002)the Russian Science Foundation(No.23-43-00057)for financial support。
文摘Integrated printing of magnetic soft robots with complex structures using recyclable materials to achieve sustainability of the soft robots remains a persistent challenge.Here,we propose a kind of ferromagnetic fibers that can be used to print soft robots with complex structures.These ferromagnetic fibers are recyclable and can make soft robots sustainable.The ferromagnetic fibers based on thermoplastic polyurethane(TPU)/NdFeB hybrid particles are extruded by an extruder.We use a desktop three-dimensional(3D)printer to demonstrate the feasibility of printing two-dimensional(2D)and complex 3D soft robots.These printed soft robots can be recycled and reprinted into new robots once their tasks are completed.Moreover,these robots show almost no difference in actuation capability compared to prior versions and have new functions.Successful applications include lifting,grasping,and moving objects,and these functions can be operated untethered wirelessly.In addition,the locomotion of the magnetic soft robot in a human stomach model shows the prospect of medical applications.Overall,these fully recyclable ferromagnetic fibers pave the way for printing and reprinting sustainable soft robots while also effectively reducing e-waste and robotics waste materials,which is important for resource conservation and environmental protection.
基金funded by the National Natural Science Foundation of China(52004201,52274143,52204153)China Postdoctoral Science Foundation(2021T140551).
文摘Coal-rock interface identification technology was pivotal in automatically adjusting the shearer's cutting drum during coal mining.However,it also served as a technical bottleneck hindering the advancement of intelligent coal mining.This study aimed to address the poor accuracy of current coal-rock identification technology on comprehensive working faces,coupled with the limited availability of coal-rock datasets.The loss function of the SegFormer model was enhanced,the model's hyperparameters and learning rate were adjusted,and an automatic recognition method was proposed for coal-rock interfaces based on FL-SegFormer.Additionally,an experimental platform was constructed to simulate the dusty environment during coal-rock cutting by the shearer,enabling the collection of coal-rock test image datasets.The morphology-based algorithms were employed to expand the coal-rock image datasets through image rotation,color dithering,and Gaussian noise injection so as to augment the diversity and applicability of the datasets.As a result,a coal-rock image dataset comprising 8424 samples was generated.The findings demonstrated that the FL-SegFormer model achieved a Mean Intersection over Union(MIoU)and mean pixel accuracy(MPA)of 97.72%and 98.83%,respectively.The FLSegFormer model outperformed other models in terms of recognition accuracy,as evidenced by an MloU exceeding 95.70% of the original image.Furthermore,the FL-SegFormer model using original coal-rock images was validated from No.15205 working face of the Yulin test mine in northern Shaanxi.The calculated average error was only 1.77%,and the model operated at a rate of 46.96 frames per second,meeting the practical application and deployment requirements in underground settings.These results provided a theoretical foundation for achieving automatic and efficient mining with coal mining machines and the intelligent development of coal mines.
基金Project(2011BAE22B05)supported by the National Science and Technology Pillar Program during the 12th Five-year Plan of China
文摘Combustion noise takes large proportion in diesel engine noise and the studies of its influence factors play an important role in noise reduction. Engine noise and cylinder pressure measurement experiments were carried out. And the improved attenuation curves were obtained, by which the engine noise was predicted. The effect of fuel injection parameters in combustion noise was investigated during the combustion process. At last, the method combining single variable optimization and multivariate combination was introduced to online optimize the combustion noise. The results show that injection parameters can affect the cylinder pressure rise rate and heat release rate, and consequently affect the cylinder pressure load and pressure oscillation to influence the combustion noise. Among these parameters, main injection advance angle has the greatest influence on the combustion noise, while the pilot injection interval time takes the second place, and the pilot injection quantity is of minimal impact. After the optimal design of the combustion noise, the average sound pressure level of the engine is distinctly reduced by 1.0 d B(A) generally. Meanwhile, the power, emission and economy performances are ensured.
基金the National Natural Science Foundation of China through Grant No.51805470the Fundamental Research Funds for the Central Universities through Grant No.2018QNA4013the Youth Funds of the State Key Laboratory of Fluid Power and Mechatronic Systems(Zhejiang University)through Grant No.SKLoFP-QN-1801.
文摘Valves are widely used in various working conditions for their flow control functions,and the cavitation inside valves has been investigated owing to its harm to the valve itself and the connecting downstream parts.This paper presents a comprehensive review of the progress that has been achieved in the past years about cavitation in valves including both mechanical heart valves and control valves.The review is divided in the following parts,namely the location where there is a high possibility of the occurrence of cavitation,the parameters that affect cavitation intensity,and the methods to minimize cavitation intensity.It should be noticed that although simulation has been widely used,advanced experiments are still needed in order to obtain accurate analysis of cavitation in valves and the cavitation model still needs to be improved.
基金Projects(52004145,51904164)supported by the National Natural Science Foundation of ChinaProject(ZR2020QE119)supported by the Natural Science Foundation of Shandong Province,ChinaProject(SICGM202107)supported by the Open Fund of the Key Laboratory of Mining Disaster Prevention and Control,China。
文摘For a deeper understanding of the deformation failure behavior of jointed rock, numerical compression simulations are carried out on a rock specimen containing non-persistent joints under confining pressure with the bondedparticle model. The microscopic parameters which can reflect the macroscopic mechanical properties and failure behavior of artificial jointed specimens are firstly calibrated. Then, the influence of joint inclination and confining pressure on stress-strain curves, crack patterns, and contact force distributions of jointed rock are investigated. The simulation results show that both the compressive strength and elastic modulus of the specimens increase with increasing confining pressure, and these two mechanical parameters decrease first and then increase with the increase of joints inclination. The sensitivity of strength and elastic modulus to confining pressure is not the same in different joints inclinations, which has the least impact on specimens with α=90°. Under low confining pressure, the failure modes are controlled by the joint inclination. As the confining pressure increased, the initiation and propagation of tensile crack are gradually inhibited, and the failure mode is transferred from tensile failure to shear-compression failure. Finally, the reinforcement effect of prestressed bolt support on engineering fractured rock mass is discussed.
基金Projects(51861034,51601167)supported by the National Natural Science Foundation of ChinaProject(2020GY-262)supported by the Science and Technology Department of Shaanxi Province,China+1 种基金Project(2019-86-1)supported by the Technology Bureau of Yulin,ChinaProject(20GK06)supported by the High-level Talent Program of Yulin University,China。
文摘The influence of multipass high rotating speed friction stir processing(FSP)on the microstructure evolution,corrosion behavior,and tensile properties of the stirred zone(SZ)was investigated by EBSD,TEM,SEM,electrochemical workstation and electronic universal testing machine.The mean grain size of the SZ is significantly refined,and it increases with the increase of the processing pass.In addition to an obvious increase in the number,the distribution ofβ-Al12Mg17 precipitates also becomes more uniform and dispersed with increasing the processing pass.Compared with the as-received AZ31 alloy,the tensile properties of the SZ are hardly improved,but the corrosion resistances are significantly enhanced.The corrosion potential of the SZ prepared by 4-pass FSP is increased from−1.56 V for the unprocessed AZ31 alloy to−1.19 V,while the corrosion current is decreased from 1.55×10^−4 to 5.47×10^−5 A.
基金the National Key Research and Development Program of China(2017YFC1103900)the National Natural Science Foundation of China(22075244 and 51722306)+1 种基金Natural Science Foundation of Zhejiang Province(LZ22E030001)Shanxi-Zheda Institute of Advanced Materials and Chemical Engi-neering(2021SZ-TD009).
文摘Many natural fibers are lightweight and display remarkable strength and toughness.These properties originate from the fibers’hierarchical structures,assembled from the molecular to macroscopic scale.The natural spinning systems that produce such fibers are highly energy efficient,inspiring researchers to mimic these processes to realize robust artificial spinning.Significant developments have been achieved in recent years toward the preparation of high-performance bio-based fibers.Beyond excellent mechanical properties,bio-based fibers can be functionalized with a series of new features,thus expanding their sophisticated applications in smart textiles,electronic sensors,and biomedical engineering.Here,recent progress in the construction of bio-based fibers is outlined.Various bioinspired spinning methods,strengthening strategies for mechanically strong fibers,and the diverse applications of these fibers are discussed.Moreover,challenges in reproducing the mechanical performance of natural systems and understanding their dynamic spinning process are presented.Finally,a perspective on the development of biological fibers is given.
文摘The gasification kinetic modelling of two Victorian brown coal(Yallourn and Maddingley)chars and the validity for entrained flow gasification were investigated in this study.The study was conducted in a thermogravimetric analyzer(TGA)at 750–1100℃,30%–90%CO_(2)concentration using different char particle sizes within 20–106 mm.It was found that random pore model and modified volumetric model are applicable for TGA results,but volumetric model and grain model are not.The effect of particle size under106 mm on gasification rate is very limited.Activation energies of Maddingley char and Yallourn char in CO_(2)gasification are 219–220 and 197–208 k J/mol,respectively.The pre-exponential factors are in the same order of magnitude,and they increased as particle size decreased.A mathematical model was developed to predict carbon conversion over time for entrained flow gasification of Victorian brown coal chars at 1000–1400℃.
基金supported by the National Natural Science Foundation of China (No. 51722604)the National Program for Support of Top-notch Young Professionals+1 种基金the financial support by the startup funding from the University of Nevadathe Australian Research Council for partial support
文摘Photothermal membrane distillation(MD)is a promising technology for desalination and water purification.However,solar-thermal conversion suffers from low energy efficiency(a typical solar-water efficiency of ~50%),while complex modifications are needed to reduce membrane fouling.Here,we demonstrate a new concept of solar vapour gap membrane distillation(SVGMD)synergistically combining self-guided water transport,localized heating,and separation of membrane from feed solution.A free-standing,multifunctional light absorber based on graphene array is custom-designed to locally heat the thin water layer transporting through graphene nanochannels.The as-generated vapour passes through a gap and condenses,while salt/contaminants are rejected before reaching the membrane.The high solar-water efficiency(73.4% at 1 sun),clean water collection ratio(82.3%),excellent anti-fouling performance,and stable permeate flux in continuous operation over 72 h are simultaneously achieved.Meanwhile,SVGMD inherits the advantage of MD in microorganism removal and water collection,enabling the solar-water efficiency 3.5 times higher compared to state-of-the-art solar vapour systems.A scaled system to treat oil/seawater mixtures under natural sunlight is developed with a purified water yield of 92.8 kg m-2 day-1.Our results can be applied for diverse mixed-phase feeds,leading to the next-generation solar-driven MD technology.
基金Supported by National Natural Science Foundation of China(Grant Nos.52076186,51839010).
文摘Double-suction centrifugal pumps have been applied extensively in many areas,and the significance of pressure fluctuations inside these pumps with large power is becoming increasingly important.In this study,a double-suction centrifugal pump with a high-demand for vibration and noise was redesigned by increasing the flow uniformity at the impeller discharge,implemented by combinations of more than two parameters.First,increasing the number of the impeller blades was intended to enhance the bounding effect that the blades imposed on the fluid.Subsequently,increasing the radial gap between the impeller and volute was applied to reduce the rotor-stator interaction.Finally,the staggered arrangement was optimized to weaken the efficacy of the interference superposition.Based on numerical simulation,the steady and unsteady characteristics of the pump models were calculated.From the fluctuation analysis in the frequency domain,the dimensionless pressure fluctuation amplitude at the blade passing frequency and its harmonics,located on the monitoring points in the redesigned pumps(both with larger radial gap),are reduced a lot.Further,in the volute of the model with new impellers staggered at 12°,the average value for the dimensionless pressure fluctuation amplitude decreases to 6%of that in prototype pump.The dimensionless rootmean-square pressure contour on the mid-span of the impeller tends to be more uniform in the redesigned models(both with larger radial gap);similarly,the pressure contour on the mid-section of the volute presents good uniformity in these models,which in turn demonstrating a reduction in the pressure fluctuation intensity.The results reveal the mechanism of pressure fluctuation reduction in a double-suction centrifugal pump,and the results of this study could provide a reference for pressure fluctuation reduction and vibration performance reinforcement of doublesuction centrifugal pumps and other pumps.
基金supported by the National Natural Science Foundation of China (No. 51722604)Zhejiang Provincial Natural Science Foundation of China (No. LR17E060002)
文摘Electric double-layer capacitors(EDLCs) are advanced electrochemical devices for energy storage and have attracted strong interest due to their outstanding properties. Rational optimization of electrode–electrolyte interactions is of vital importance to enhance device performance for practical applications. Molecular dynamics(MD) simulations could provide theoretical guidelines for the optimal design of electrodes and the improvement of capacitive performances, e.g., energy density and power density. Here we discuss recent MD simulation studies on energy storage performance of electrode materials containing porous to nanostructures. The energy storage properties are related to the electrode structures, including electrode geometry and electrode modifications. Altering electrode geometry, i.e., pore size and surface topography,can influence EDL capacitance. We critically examine different types of electrode modifications, such as altering the arrangement of carbon atoms, doping heteroatoms and defects, which can change the quantum capacitance. The enhancement of power density can be achieved by the intensified ion dynamics and shortened ion pathway.Rational control of the electrode morphology helps improve the ion dynamics by decreasing the ion diffusion pathway. Tuning the surface properties(e.g., the affinity between the electrode and the ions) can affect the ionpacking phenomena. Our critical analysis helps enhance the energy and power densities of EDLCs by modulating the corresponding electrode structures and surface properties.
基金supported by National Natural Science Foundation of China(No.51576174)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20120101110099)the Fundamental Research Funds for the Central Universities(No.2015FZA4011)
文摘In this work, a novel direct current （DC） atmospheric pressure rotating gliding arc （RGA） plasma reactor has been developed for plasma-assisted chemical reactions. The influence of the gas composition and the gas flow rate on the arc dynamic behaviour and the formation of reactive species in the N2 and air gliding arc plasmas has been investigated by means of electrical signals, high speed photography, and optical emission spectroscopic diagnostics. Compared to conventional gliding arc reactors with knife-shaped electrodes which generally require a high flow rate （e.g., 10-20 L/min） to maintain a long arc length and reasonable plasma discharge zone, in this RGA system, a lower gas flow rate （e.g., 2 L/min） can also generate a larger effective plasma reaction zone with a longer arc length for chemical reactions. Two different motion patterns can be clearly observed in the N2 and air RGA plasmas. The time-resolved arc voltage signals show that three different arc dynamic modes, the arc restrike mode, takeover mode, and combined modes, can be clearly identified in the RGA plasmas. The occurrence of different motion and arc dynamic modes is strongly dependent on the composition of the working gas and gas flow rate.
基金financially supported by the National Natural Science Foundation of China(Grant No.52074258,Grant No.41941018,Grant No.51974289,and Grant No.51874232)the Natural Science Basic Research Program of Shaanxi Province(Shaanxi Coal and Chemical Industry Group Co.,Ltd.Joint Fund Project,Grant No.2021JLM-06)the open project of State Key Laboratory of Shield Machine and Boring Technology(Grant No.E01Z440101)。
文摘Soft rock squeezing deformation mainly consists of pre-peak damage-dilatancy and post-peak fracture-bulking at the excavation unloading instant,and creep-dilatancy caused by time-dependent damage and fracturing.Based on the classic elastoplastic and Perzyna over-stress viscoplastic theories,as well as triaxial unloading confining pressure test and triaxial unloading creep test results,an elastoplastic and viscoplastic damage constitutive model is established for the short-and long-term dilatancy and fracturing behavior of soft rock squeezing deformation.Firstly,the criteria for each deformation and failure stage are expressed as a linear function of confining pressure.Secondly,the total damage evolution equation considering time-dependent damage is proposed,including the initial damage produced at the excavation instant,in which the damage variable increases exponentially with the lateral strain,and creep damage.Thirdly,a transient five-stages elasto-plastic constitutive equation for the short-term deformation after excavation that comprised of elasticity,pre-peak damage-dilatancy,post-peak brittle-drop,linear strain-softening,and residual perfectly-plastic regimes is developed based on incremental elasto-plastic theory and the nonassociated flow rule.Fourthly,regarding the timedependent properties of soft rock,based on the Perzyna viscoplastic over-stress theory,a viscoplastic damage model is set up to capture creep damage and dilatancy behavior.Viscoplastic strain is produced when the stress exceeds the initial static yield surface fs;the distance between the static yield surface fs and the dynamic yield surface fd determines the viscoplastic strain rate.Finally,the established constitutive model is numerically implemented and field applied to the-848 m belt conveyer haulage roadway of Huainan Panyidong Coal Mine.Laboratory test results and in-situ monitoring results validate the rationality of the established constitutive model.The presented model takes both the transient and time-dependent damage and fracturing into consideration.
基金Supported by the Natural Science Foundation of China,Zhejiang Province(LY16B060003)the National Natural Science Foundation of China(21776246).
文摘A coaxial mixer consisting of an anchor and a Rushton turbine was selected as the research object,whose solid suspension characteristics were studied with the help of Computational Fluid Dynamics(CFD)method.Based on the Eulerian–Eulerian method and modified Brucato drag model,the just-suspension speed of impeller was predicted,and the simulation results were in good agreement with the experimental data.The quality of solid suspension under different rotation modes was also compared,and the results showed the coaxial mixer operating under co-rotation mode could get the best performance,and a larger anchor speed was beneficial to solid suspension by enhancing the turbulent intensity at the bottom.Compared with the anchor,the inner Rushton turbine played a dominant role in solid suspension due to its high rotational speed,whereas an extremely high inner impeller speed would make the uniformity of solid distributions become worse.Additionally,the effects of solid phase properties were also investigated,the results revealed that the higher the overall solid volume fraction and the smaller the Shields number,the worse the performance of solid suspension,meanwhile the solid suspension was more susceptible to solid density compared with particle diameter within the same Shields number gradient.
基金funding from the National Natural Science Foundation of China (22178301,21938011,51876186and 52150410417)the funding from the Natural Science Foundation of Zhejiang Province (LR21B060003 and LZ19E060002)+1 种基金grant from Science Technology Department of Zhejiang Province (2023C01182)supported by Shanxi Institute of Zhejiang University for New Materials and Chemical Industry(2022SZ-TD005)。
文摘Polymer-derived ceramic(PDC) thin films are promising wear-resistant coatings for protecting metals and carbon-carbon composites from corrosion and oxidation.However,the high pyrolysis temperature hinders the applications on substrate materials with low melting points.We report a new synthesis route for PDC coatings using initiated chemical vapor deposited poly(1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane)(pV_3D_3) as the precurs or.We investigated the changes in siloxane moieties and the network topology,and proposed a three-stage mechanism for the thermal annealing process.The rise of the connectivity number for the structures obtained at increased annealing temperatures was found with strong correlation to the enhanced mechanical properties and thermal conductivity.Our PDC films obtained via annealing at 850℃ exhibit at least 14.6% higher hardness than prior reports for PDCs synthesized below 1100℃.Furthermore,thermal conductivity up to 1.02 W(mK)^(-1) was achieved at the annealing temperature as low as 700℃,which is on the same order of magnitude as PDCs obtained above 1100℃.Using minimum thermal conductivity models,we found that the thermal transport is dominated by diffusons in the films below the percolation of rigidity,while ultra-short mean-free path phonons contribute to the thermal conductivity of the films above the percolation threshold.The findings of this work provide new insights for the development of wear-resistant and thermally conductive PDC thin films for durable protection coatings.
基金Project(51076062)supported by the National Natural Science Foundation of China
文摘A mathematical model was developed to predict the maximum heat transfer capacity of high temperature heat pipe with triangular grooved wick. The effects of the inclination angle and geometry structure were considered in the proposed model.Maximum heat transfer capacity was also investigated experimentally. The model was validated by comparing with the experimental results. The maximum heat transfer capacity increases with the vapor core radius increasing. Compared with the inclination angle of0°, the maximum heat transfer capacity increases at the larger inclination angle, and the change with temperature is larger. The performance of heat pipe with triangular grooved wick is greatly influenced by gravity, so it is not recommended to be applied to the dish solar heat pipe receiver.
基金provided by the National Natural Science Foundation of China (No.11002021)the Doctoral Subject,Foundation of the Ministry of Education of China (No.20070008012)+1 种基金the National High Technology Research and Development Program of China (No.2008AA062104)Team Program for Key Scientific and Technological innovation,Shaanxi Province of China (No.2013KCT-16)
文摘Horizontal section top-coal(HSTCC)caving offers a powerful method to efficiently excavate rude coal in steep and thick seams,and pre-blasting weakening has a profound effect on pursuing great production,high efficiency and good benefit under particular conditions like a small-scale working face with large-scale sectional caving height.+564-level HSTCC working face in B3–6coal seams of Jiangou Colliery in Urumqi was taken as study case for in situ industrial experiment.Total thickness of seams in the study case is about 50.0 m and average angel here is over 83°.In the industrial experiments,at first we adopted continuous charge machine and emulsion matrix explosive to substitute for traditional blasting schemes for specific geological settings in the study case.Hybrid analyses and assessments with blasting crack propagation analysis,abutment pressure monitoring prediction and economical benefit assessment were attributed to be able to attest pre-blasting weakening effects practically.Meanwhile crack propagation analysis after pre-blasting weakening showed that in all triple monitoring bore holes rock masses of top-coal would be fallen into three stages from the bottom up:fracture zone,plastic zone and elastic zone generally,and fracture toughness respectively in correspondent zones was calculated by the analytical formula:0.5616–0.8806,0.6403–0.9541 and0.7535–1.1900 MPa m1/2after pre-blasting weakening.Pressure monitoring prediction and economical benefit assessment also indicated that it was necessary to introduce the pre-blasting weakening with predominant blasting scheme from both views.For excavation in extremely steep and thick coal seams,relevant results would be a useful tool to study the mechanism of pre-blasting weakening both qualitatively and quantitatively.
