Laser technology holds significant promise for enhancing rock-breaking efficiency.Experimental investigations were carried out on sandstone subjected to laser radiation,aiming to elucidate its response mechanism to su...Laser technology holds significant promise for enhancing rock-breaking efficiency.Experimental investigations were carried out on sandstone subjected to laser radiation,aiming to elucidate its response mechanism to such radiation.The uniaxial compressive strength of sandstone notably decreases by 22.1%–54.7%following exposure to a 750 W laser for 30 s,indicating a substantial weakening effect.Furthermore,the elastic modulus and Poisson ratio of sandstone exhibit an average decrease of 33.7%and 25.9%,respectively.Simultaneously,laser radiation reduces the brittleness of sandstone,increases the dissipated energy proportion,and shifts the failure mode from tensile to tension-shear composite failure.Following laser radiation,both the number and energy of acoustic emission events in the sandstone register a substantial increase,with a more dispersed distribution of these events.In summary,laser radiation induces notable damage to the mechanical properties of sandstone,leading to a substantial decrease in elastic energy storage capacity.Laser rock breaking technology is expected to be applied in hard rock breaking engineering to significantly reduce the difficulty of rock breaking and improve rock breaking efficiency.展开更多
Blasting-induced cracks in the rock surrounding deeply buried tunnels can result in water gushing and rock mass collapse,posing significant safety risks.However,previous theoretical studies on the range of blasting-in...Blasting-induced cracks in the rock surrounding deeply buried tunnels can result in water gushing and rock mass collapse,posing significant safety risks.However,previous theoretical studies on the range of blasting-induced cracks often ignore the impact of the in-situ stress,especially that of the intermediate principal stress.The particle displacement−crack radius relationship was established in this paper by utilizing the blasthole cavity expansion equation,and theoretical analytical formulas of the stress−displacement relationship and the crack radius were derived with unified strength theory to accurately assess the range of cracks in deep surrounding rock under a blasting load.Parameter analysis showed that the crushing zone size was positively correlated with in-situ stress,intermediate principal stress,and detonation pressure,whereas negatively correlated with Poisson ratio and decoupling coefficient.The dilatancy angle-crushing zone size relationship exhibited nonmonotonic behavior.The relationships in the crushing zone and the fracture zone exhibited opposite trends under the influence of only in-situ stress or intermediate principal stress.As the in-situ stress increased from 0 to 70 MPa,the rate of change in the crack range and the attenuation rate of the peak vibration velocity gradually slowed.展开更多
Aim To research on a solid cemented carbide multi facet drill for drilling high strength steel. Methods Assimilating some features of multi facet drill edge structures, through systematic drilling experiments, a n...Aim To research on a solid cemented carbide multi facet drill for drilling high strength steel. Methods Assimilating some features of multi facet drill edge structures, through systematic drilling experiments, a new type of solid cemented carbide drill was developed and the drill geometry was optimized. Results With the new type drill,the drilling force decreases by 10%-20%, the drilling productivity (drilled holes per hour) increases by 2-3 times, and the drilling precision and surface finish increase by one level. Conclusion The new type drill possesses excellent drilling performance.展开更多
In machining the particle reinforced aluminum based composite material with high Si content using the cobalt-cemented tungsten carbide micro cutting tools, diamond like carbon （DLC） films are deposited on cobalt-cem...In machining the particle reinforced aluminum based composite material with high Si content using the cobalt-cemented tungsten carbide micro cutting tools, diamond like carbon （DLC） films are deposited on cobalt-cemented tungsten carbide micro-drills with two-step pretreatment method. Characteristics of DLC coated tools are investigated in bias-enhanced HFCVD system with the optimized hot filament arrangement. The optimization deposition technology is obtained and the wear mechanism of cutting tools is analyzed. The drilling performance of DLC coated tools is verified by the experiments of cutting particle reinforced aluminum based composite material （Si 15% in volume） compared with uncoated ones. Experimental results show that the two-step pretreatment method is appropriate for complex shaped cemented carbide substrates and ensures the good adhesive strength between the diamond film and the substrate. The cutting performance of DLC coated tool is enhanced 10 times when machining the Si particle reinforced aluminum based metal matrix composite compared with that of uncoated ones under the same cutting conditions.展开更多
High strength reinforced concrete drilling shaft linings have been adopted to solve the difficult problem of supporting coal drilling shafts penetrating through thick top soils. Through model experiments the stress an...High strength reinforced concrete drilling shaft linings have been adopted to solve the difficult problem of supporting coal drilling shafts penetrating through thick top soils. Through model experiments the stress and strength of such shaft linings are studied. The test results indicate that the load beating capacity of the shaft lining is very high and that the main factors affecting the load bearing capacity are the concrete strength, the ratio of lining thickness to inner radius and the reinforcement ratio. Based on the limit equilibrium conditions and the strength theory of concrete under multi-axial compressive stressed state, a formula for calculating the load-beating capacity of a high strength reinforced concrete shaft lining was obtained. Because the concrete in a shaft lining is in a multi-axial compressive stress state the compressive strength increases to a great extent compared to uni-axial loading. Based on experiment a formula for the gain factor in compressive strength was obtained： it can be used in the structural design of the shaft lining. These results have provided a basis for sound engineering practice when designing this kind of shaft lining structure.展开更多
During well drilling process,original stress state of hard brittle shale will be changed due to stress redistribution and concentration,which leads to stress damage phenomenon around the borehole.Consequently,drilling...During well drilling process,original stress state of hard brittle shale will be changed due to stress redistribution and concentration,which leads to stress damage phenomenon around the borehole.Consequently,drilling fluid will invade into formation along the tiny cracks induced by stress damage,and then weaken the strength of hard brittle shale.Based on this problem,a theoretical model was set up to discuss damage level of shale under uniaxial compression tests using acoustic velocity data.And specifically,considering the coupled effect of stress damage and drilling fluid,the relationship between hard brittle shale strength and elapsed time was analyzed.展开更多
This research presents experimental data on mechanical foam bursting device,based on the high speed of air fluid impinging insidethe foam bursting device,foam bubbles disrupted as a consequence of pressures changed ve...This research presents experimental data on mechanical foam bursting device,based on the high speed of air fluid impinging insidethe foam bursting device,foam bubbles disrupted as a consequence of pressures changed very quickly as shear force and their impact forces.Experimental data on foam-bursting capacity have been presented.Designed device can provide effective foam bursting on collapse foam.展开更多
This paper proposes an analytical model to describe rock drilling processes using drag bits and rotary drills, and to induce relations among rock properties, bit shapes, and drilling parameters （rotary speed, thrust,...This paper proposes an analytical model to describe rock drilling processes using drag bits and rotary drills, and to induce relations among rock properties, bit shapes, and drilling parameters （rotary speed, thrust, torque, and stroke）. In this model, a drilling process is divided into successive cycles. Each cycle includes two motions： feed and cutting. According to this model, drilling torque includes four components generated from cutting, friction, feed, and idle running respectively, the first three items are all proportional to the UCS （uniaxial compressive strength） when the penetration rate is constant. Laboratory tests verified the correctness and effectiveness of the proposed model qualitatively. Especially, the influence of friction on the flank face and the idle running was confirmed. Field experiments were performed. The results showed good correlation between the torque, penetration rate, and UCS. The proposed model and equations engender the possibility of eliminating useless components of cutting forces when investigating the relation between mechanical data and physical properties of rocks.展开更多
基金Projects(52225403,U2013603,42377143)supported by the National Natural Science Foundation of ChinaProject(2023NSFSC0004)supported by the Sichuan Science and Technology Program,China+1 种基金Project(2023YFB2390200)supported by the National Key R&D Program-Young Scientist Program,ChinaProject(RCJC20210706091948015)supported by the Shenzhen Science Foundation for Distinguished Young Scholars,China。
文摘Laser technology holds significant promise for enhancing rock-breaking efficiency.Experimental investigations were carried out on sandstone subjected to laser radiation,aiming to elucidate its response mechanism to such radiation.The uniaxial compressive strength of sandstone notably decreases by 22.1%–54.7%following exposure to a 750 W laser for 30 s,indicating a substantial weakening effect.Furthermore,the elastic modulus and Poisson ratio of sandstone exhibit an average decrease of 33.7%and 25.9%,respectively.Simultaneously,laser radiation reduces the brittleness of sandstone,increases the dissipated energy proportion,and shifts the failure mode from tensile to tension-shear composite failure.Following laser radiation,both the number and energy of acoustic emission events in the sandstone register a substantial increase,with a more dispersed distribution of these events.In summary,laser radiation induces notable damage to the mechanical properties of sandstone,leading to a substantial decrease in elastic energy storage capacity.Laser rock breaking technology is expected to be applied in hard rock breaking engineering to significantly reduce the difficulty of rock breaking and improve rock breaking efficiency.
基金Project(2021JJ10063)supported by the Natural Science Foundation of Hunan Province,ChinaProject(202115)supported by the Science and Technology Progress and Innovation Project of Hunan Provincial Department of Transportation,ChinaProject(2021K094-Z)supported by the Science and Technology Research and Development Program of China Railway Guangzhou Group Co.,Ltd。
文摘Blasting-induced cracks in the rock surrounding deeply buried tunnels can result in water gushing and rock mass collapse,posing significant safety risks.However,previous theoretical studies on the range of blasting-induced cracks often ignore the impact of the in-situ stress,especially that of the intermediate principal stress.The particle displacement−crack radius relationship was established in this paper by utilizing the blasthole cavity expansion equation,and theoretical analytical formulas of the stress−displacement relationship and the crack radius were derived with unified strength theory to accurately assess the range of cracks in deep surrounding rock under a blasting load.Parameter analysis showed that the crushing zone size was positively correlated with in-situ stress,intermediate principal stress,and detonation pressure,whereas negatively correlated with Poisson ratio and decoupling coefficient.The dilatancy angle-crushing zone size relationship exhibited nonmonotonic behavior.The relationships in the crushing zone and the fracture zone exhibited opposite trends under the influence of only in-situ stress or intermediate principal stress.As the in-situ stress increased from 0 to 70 MPa,the rate of change in the crack range and the attenuation rate of the peak vibration velocity gradually slowed.
文摘Aim To research on a solid cemented carbide multi facet drill for drilling high strength steel. Methods Assimilating some features of multi facet drill edge structures, through systematic drilling experiments, a new type of solid cemented carbide drill was developed and the drill geometry was optimized. Results With the new type drill,the drilling force decreases by 10%-20%, the drilling productivity (drilled holes per hour) increases by 2-3 times, and the drilling precision and surface finish increase by one level. Conclusion The new type drill possesses excellent drilling performance.
文摘In machining the particle reinforced aluminum based composite material with high Si content using the cobalt-cemented tungsten carbide micro cutting tools, diamond like carbon （DLC） films are deposited on cobalt-cemented tungsten carbide micro-drills with two-step pretreatment method. Characteristics of DLC coated tools are investigated in bias-enhanced HFCVD system with the optimized hot filament arrangement. The optimization deposition technology is obtained and the wear mechanism of cutting tools is analyzed. The drilling performance of DLC coated tools is verified by the experiments of cutting particle reinforced aluminum based composite material （Si 15% in volume） compared with uncoated ones. Experimental results show that the two-step pretreatment method is appropriate for complex shaped cemented carbide substrates and ensures the good adhesive strength between the diamond film and the substrate. The cutting performance of DLC coated tool is enhanced 10 times when machining the Si particle reinforced aluminum based metal matrix composite compared with that of uncoated ones under the same cutting conditions.
基金Project 050440502 supported by the Natural Science Foundation of Anhui Province
文摘High strength reinforced concrete drilling shaft linings have been adopted to solve the difficult problem of supporting coal drilling shafts penetrating through thick top soils. Through model experiments the stress and strength of such shaft linings are studied. The test results indicate that the load beating capacity of the shaft lining is very high and that the main factors affecting the load bearing capacity are the concrete strength, the ratio of lining thickness to inner radius and the reinforcement ratio. Based on the limit equilibrium conditions and the strength theory of concrete under multi-axial compressive stressed state, a formula for calculating the load-beating capacity of a high strength reinforced concrete shaft lining was obtained. Because the concrete in a shaft lining is in a multi-axial compressive stress state the compressive strength increases to a great extent compared to uni-axial loading. Based on experiment a formula for the gain factor in compressive strength was obtained： it can be used in the structural design of the shaft lining. These results have provided a basis for sound engineering practice when designing this kind of shaft lining structure.
基金Project(U262201)supported by National Natural Science Foundation of China
文摘During well drilling process,original stress state of hard brittle shale will be changed due to stress redistribution and concentration,which leads to stress damage phenomenon around the borehole.Consequently,drilling fluid will invade into formation along the tiny cracks induced by stress damage,and then weaken the strength of hard brittle shale.Based on this problem,a theoretical model was set up to discuss damage level of shale under uniaxial compression tests using acoustic velocity data.And specifically,considering the coupled effect of stress damage and drilling fluid,the relationship between hard brittle shale strength and elapsed time was analyzed.
文摘This research presents experimental data on mechanical foam bursting device,based on the high speed of air fluid impinging insidethe foam bursting device,foam bubbles disrupted as a consequence of pressures changed very quickly as shear force and their impact forces.Experimental data on foam-bursting capacity have been presented.Designed device can provide effective foam bursting on collapse foam.
文摘This paper proposes an analytical model to describe rock drilling processes using drag bits and rotary drills, and to induce relations among rock properties, bit shapes, and drilling parameters （rotary speed, thrust, torque, and stroke）. In this model, a drilling process is divided into successive cycles. Each cycle includes two motions： feed and cutting. According to this model, drilling torque includes four components generated from cutting, friction, feed, and idle running respectively, the first three items are all proportional to the UCS （uniaxial compressive strength） when the penetration rate is constant. Laboratory tests verified the correctness and effectiveness of the proposed model qualitatively. Especially, the influence of friction on the flank face and the idle running was confirmed. Field experiments were performed. The results showed good correlation between the torque, penetration rate, and UCS. The proposed model and equations engender the possibility of eliminating useless components of cutting forces when investigating the relation between mechanical data and physical properties of rocks.
