In rock drilling and blasting,the misfire of electronic detonators will not only affect the rock fragmentation result but also bring serious potential safety hazards to engineering construction.An accurate and compreh...In rock drilling and blasting,the misfire of electronic detonators will not only affect the rock fragmentation result but also bring serious potential safety hazards to engineering construction.An accurate and comprehensive understanding of the failure mechanisms of electronic detonators subjected to impact loading is of great significance to the reliability design and field safety use of electronic detonators.The spatial distribution characteristics and failure modes of misfired electronic detonators under different application scenarios are statistically analysed.The results show that under high impact loads,electronic detonators will experience failure phenomena such as rupture of the fuse head,fracture of the bridge wire,falling off of the solder joint,chip module damage and insufficient initiation energy after deformation.The lack of impact resistance is the primary cause of misfire of electronic detonators.Combined with the underwater impact resistance test and the impact load test in the adjacent blasthole on site,the formulas of the impact failure probability of the electronic detonator under different stress‒strength distribution curves are deduced.The test and evaluation method of the impact resistance of electronic detonators based on stress‒strength interference theory is proposed.Furthermore,the impact failure model of electronic detonators considering the strength degradation effect under repeated random loads is established.On this basis,the failure mechanism of electronic detonators under different application environments,such as open-pit blasting and underground blasting,is revealed,which provides scientific theory and methods for the reliability analysis,design and type selection of electronic detonators in rock drilling and blasting.展开更多
The relatively high stress probably leads to generation of a fractured or even instable area around a working coalface. Also, the generated weak area often evolves into an easy-infiltrating field of water/gas to great...The relatively high stress probably leads to generation of a fractured or even instable area around a working coalface. Also, the generated weak area often evolves into an easy-infiltrating field of water/gas to greatly increase probability of accident occurrence. To reveal the distribution of high stress around working faces, we put forward the mode-I-crack compression model. In this model, the goaf following a working face is regarded as a mode-I crack in an infinite plate, and the self-gravity of overlaying strata is transformed into an uniform pressure applied normal to the upper edge of the model crack. Solving this problem is based on the Westergaard complex stress function. For comparison, the software RFPA-2D is also employed to simulate the same mining problem, and furthermore extendedly to calculate the stress interference induced by the simultaneous advances of two different working faces. The results show that, the area close to a working face or the goaf tail has the maximum stress, and the stress is distributed directly proportional to the square root of the advance and inversely proportional to the square root of the distance to the working face. The simultaneous advances of two neighboring working faces in different horizontals can lead to extremely high resultant stress in an interference area.展开更多
Based on a geology-engineering sweet spot evaluation,the high-quality reservoir zones and horizontal well landing points were determined.Subsequently,fracture propagation and production were simulated with a multilaye...Based on a geology-engineering sweet spot evaluation,the high-quality reservoir zones and horizontal well landing points were determined.Subsequently,fracture propagation and production were simulated with a multilayer fracturing scenario.The optimal hydraulic fracturing strategy for themultilayer fracturing networkwas determined by introducing a vertical asymmetry factor.This strategy aimed to minimize stress shadowing effects in the vertical direction while maximizing the stimulated reservoir volume(SRV).The study found that the small vertical layer spacing of high-quality reservoirs and the presence of stress-masking layers(with a stress difference of approximately 3∼8 MPa)indicate that interlayer stress interference from multilayers and multiwells fracturing between neighboring developed formations could affect the longitudinal propagation of the reservoirs.In addition,this study investigated well spacing optimization by comparing uniformly spaced wells(100–300 m)with asymmetric spaced wells(200 m upper layer,250 m lower layer).Numerical results indicated that asymmetric spaced well placement yielded the largest stimulated reservoir volume(SRV)of 73,082 m^(3),representing a 65.42%increase compared to 100 m spaced wells.Furthermore,four different hydraulic fracturing sequences(interlayer,up-down,down-up,and center-edge)were compared for multilayer and multiwell networks.The center-edge sequence exhibited the lowest vertical asymmetry factor(0.71)and the least stress shadowing effects compared to the other sequences(0.78 for interlayer,0.75 for up-down,and 0.76 for down-up).This sequence also achieved the largest SRV(486,194m^(3)),representing an 11.87%increase compared to the down-up sequence.Therefore,the center-edge fracturing sequence is recommended formultilayer development in this block.These results offer valuable insights for optimizing well placement and fracturing sequence design in multilayer well networks,ultimately advancing the development of multilayer fracturing technology in the region.展开更多
For deep CBM productivity improvement,a technical concept of conducting multi-well synchronous hydraulic conformance fracturing was proposed based on its geological characteristics.First,a mathematical model for multi...For deep CBM productivity improvement,a technical concept of conducting multi-well synchronous hydraulic conformance fracturing was proposed based on its geological characteristics.First,a mathematical model for multi-fracture induced stress was established by using the boundary element displacement discontinuity method,to simulate the distribution of induced stress field in deep coal beds and analyze the possibility of the formation of complex fracture networks induced by the hydraulic conformance fracturing.Then,the propagation situation of fracture networks interfered by stress and its influencing factors were studied by using the discrete element method.And finally,the feasibility of synchronous hydraulic conformance fracturing technology was verified through tri-axial fracturing experiment and field application.It is shown that by virtue of synchronous hydraulic conformance fracturing technology,stress interference area and strength are increased,so horizontal major stress difference is decreased and even the direction of earth stress is changed regionally,which is conducive to the connection of developed face cleats and butt cleats in coal rocks,so as to form large,efficient and complex fracture networks.Furthermore,the favorable conditions for the formation of complex fracture networks by hydraulic conformance fracturing include lower initial horizontal major stress difference,low Poisson's ratio,short well spacing and low fracturing fluid viscosity and high net pressure inside the fractures.Finally,it is shown from the 3D true physical simulation experiments that by virtue of this synchronous hydraulic conformance fracturing technology,natural fractures in coal rocks can be connected sufficiently,and consequently complex fracture networks composed of hydraulic fractures,face cleats and butt cleats are created.Based on these research results,a set of optimization design method for the synchronous hydraulic conformance fracturing of deep coal beds was proposed.Five vertical wells located in the deep coal beds of North Shizhuang Block in the Southern Qinshui Basin were chosen for the pilot test.It is indicated from fracture monitoring and drainage/production data that the stimulated reservoir volume(SRV)of synchronous hydraulic fractured wells is large and its fracture network is complex;and that compared with the conventionally fractured wells,the synchronous hydraulic fractured well is earlier in gas breakthrough,and higher and more stable in production rates and casing pressure and its regional pressure drop even spreads to the adjacent wells,so that their production rates are remarkably raised.展开更多
To comprehensively consider the effects of strength degeneration and failure correlation, an improved stress–strength interference （SSI） model is proposed to analyze the reliability of aeroengine blades with the fa...To comprehensively consider the effects of strength degeneration and failure correlation, an improved stress–strength interference （SSI） model is proposed to analyze the reliability of aeroengine blades with the fatigue failure mode. Two types of TC4 alloy experiments are conducted for the study on the damage accumulation law. All the parameters in the nonlinear damage model are obtained by the tension–compression fatigue tests, and the accuracy of the nonlinear damage model is verified by the damage tests. The strength degeneration model is put forward on the basis of the Chaboche nonlinear damage theory and the Griffith fracture criterion, and determined by measuring the fatigue toughness during the tests. From the comparison of two kinds of degeneration models based on the Miner’s linear law and the nonlinear damage model respectively, the nonlinear model has a significant advantage on prediction accuracy especially in the later period of life. A time-dependent SSI reliability model is established. By computing the stress distribution using the finite element （FE） technique, the reliability of a single blade during the whole service life is obtained. Considering the failure correlation of components, a modified reliability model of aero-engine blades with common cause failure （CCF） is presented. It shows a closer and more reasonable process with the actual working condition. The improved reliability model is illustrated to be applied to aero-engine blades well, and the approach purposed in this paper is suitable for any actual machinery component of aero-engine rotor systems.展开更多
基金supported by the Chongqing Youth Talent Support Program(Cstc2022ycjh-bgzxm0079)the Chinese National Natural Science Foundation(52379128,51979152)+2 种基金Science Fund for Distinguished Young Scholars of Hubei Proivnce(2023AFA048)Educational Commission of Hubei Province of China(T2020005)the Young Top-notch Talent Cultivation Program of Hubei Province.
文摘In rock drilling and blasting,the misfire of electronic detonators will not only affect the rock fragmentation result but also bring serious potential safety hazards to engineering construction.An accurate and comprehensive understanding of the failure mechanisms of electronic detonators subjected to impact loading is of great significance to the reliability design and field safety use of electronic detonators.The spatial distribution characteristics and failure modes of misfired electronic detonators under different application scenarios are statistically analysed.The results show that under high impact loads,electronic detonators will experience failure phenomena such as rupture of the fuse head,fracture of the bridge wire,falling off of the solder joint,chip module damage and insufficient initiation energy after deformation.The lack of impact resistance is the primary cause of misfire of electronic detonators.Combined with the underwater impact resistance test and the impact load test in the adjacent blasthole on site,the formulas of the impact failure probability of the electronic detonator under different stress‒strength distribution curves are deduced.The test and evaluation method of the impact resistance of electronic detonators based on stress‒strength interference theory is proposed.Furthermore,the impact failure model of electronic detonators considering the strength degradation effect under repeated random loads is established.On this basis,the failure mechanism of electronic detonators under different application environments,such as open-pit blasting and underground blasting,is revealed,which provides scientific theory and methods for the reliability analysis,design and type selection of electronic detonators in rock drilling and blasting.
基金Projects 50774083 and 40811120546 supported by the National Natural Science Foundation of ChinaNCET-07-0803 by the Program for New Century Ex-cellent Talents in University 2005CB221502 by the National Basic Research Program of China
文摘The relatively high stress probably leads to generation of a fractured or even instable area around a working coalface. Also, the generated weak area often evolves into an easy-infiltrating field of water/gas to greatly increase probability of accident occurrence. To reveal the distribution of high stress around working faces, we put forward the mode-I-crack compression model. In this model, the goaf following a working face is regarded as a mode-I crack in an infinite plate, and the self-gravity of overlaying strata is transformed into an uniform pressure applied normal to the upper edge of the model crack. Solving this problem is based on the Westergaard complex stress function. For comparison, the software RFPA-2D is also employed to simulate the same mining problem, and furthermore extendedly to calculate the stress interference induced by the simultaneous advances of two different working faces. The results show that, the area close to a working face or the goaf tail has the maximum stress, and the stress is distributed directly proportional to the square root of the advance and inversely proportional to the square root of the distance to the working face. The simultaneous advances of two neighboring working faces in different horizontals can lead to extremely high resultant stress in an interference area.
基金supported by the National Natural Science Foundation of China(51704324,52374027)Shandong Natural Science Foundation of China(ZR2022ME025,ZR2023ME158).
文摘Based on a geology-engineering sweet spot evaluation,the high-quality reservoir zones and horizontal well landing points were determined.Subsequently,fracture propagation and production were simulated with a multilayer fracturing scenario.The optimal hydraulic fracturing strategy for themultilayer fracturing networkwas determined by introducing a vertical asymmetry factor.This strategy aimed to minimize stress shadowing effects in the vertical direction while maximizing the stimulated reservoir volume(SRV).The study found that the small vertical layer spacing of high-quality reservoirs and the presence of stress-masking layers(with a stress difference of approximately 3∼8 MPa)indicate that interlayer stress interference from multilayers and multiwells fracturing between neighboring developed formations could affect the longitudinal propagation of the reservoirs.In addition,this study investigated well spacing optimization by comparing uniformly spaced wells(100–300 m)with asymmetric spaced wells(200 m upper layer,250 m lower layer).Numerical results indicated that asymmetric spaced well placement yielded the largest stimulated reservoir volume(SRV)of 73,082 m^(3),representing a 65.42%increase compared to 100 m spaced wells.Furthermore,four different hydraulic fracturing sequences(interlayer,up-down,down-up,and center-edge)were compared for multilayer and multiwell networks.The center-edge sequence exhibited the lowest vertical asymmetry factor(0.71)and the least stress shadowing effects compared to the other sequences(0.78 for interlayer,0.75 for up-down,and 0.76 for down-up).This sequence also achieved the largest SRV(486,194m^(3)),representing an 11.87%increase compared to the down-up sequence.Therefore,the center-edge fracturing sequence is recommended formultilayer development in this block.These results offer valuable insights for optimizing well placement and fracturing sequence design in multilayer well networks,ultimately advancing the development of multilayer fracturing technology in the region.
基金Project supported by National Science and Technology Major Project“Stimulation Material Development and Well Completion Technology Research”(No.:2011ZX05042-002-001).
文摘For deep CBM productivity improvement,a technical concept of conducting multi-well synchronous hydraulic conformance fracturing was proposed based on its geological characteristics.First,a mathematical model for multi-fracture induced stress was established by using the boundary element displacement discontinuity method,to simulate the distribution of induced stress field in deep coal beds and analyze the possibility of the formation of complex fracture networks induced by the hydraulic conformance fracturing.Then,the propagation situation of fracture networks interfered by stress and its influencing factors were studied by using the discrete element method.And finally,the feasibility of synchronous hydraulic conformance fracturing technology was verified through tri-axial fracturing experiment and field application.It is shown that by virtue of synchronous hydraulic conformance fracturing technology,stress interference area and strength are increased,so horizontal major stress difference is decreased and even the direction of earth stress is changed regionally,which is conducive to the connection of developed face cleats and butt cleats in coal rocks,so as to form large,efficient and complex fracture networks.Furthermore,the favorable conditions for the formation of complex fracture networks by hydraulic conformance fracturing include lower initial horizontal major stress difference,low Poisson's ratio,short well spacing and low fracturing fluid viscosity and high net pressure inside the fractures.Finally,it is shown from the 3D true physical simulation experiments that by virtue of this synchronous hydraulic conformance fracturing technology,natural fractures in coal rocks can be connected sufficiently,and consequently complex fracture networks composed of hydraulic fractures,face cleats and butt cleats are created.Based on these research results,a set of optimization design method for the synchronous hydraulic conformance fracturing of deep coal beds was proposed.Five vertical wells located in the deep coal beds of North Shizhuang Block in the Southern Qinshui Basin were chosen for the pilot test.It is indicated from fracture monitoring and drainage/production data that the stimulated reservoir volume(SRV)of synchronous hydraulic fractured wells is large and its fracture network is complex;and that compared with the conventionally fractured wells,the synchronous hydraulic fractured well is earlier in gas breakthrough,and higher and more stable in production rates and casing pressure and its regional pressure drop even spreads to the adjacent wells,so that their production rates are remarkably raised.
基金National Science Foundation of China and Civil Aviation Administration Foundation of China(No.U1233201)National Natural Science Foundation of China(No.60879002)Tianjin Municipal Science and Technology Support Plan of China(No.10ZCKFGX03800)
文摘To comprehensively consider the effects of strength degeneration and failure correlation, an improved stress–strength interference （SSI） model is proposed to analyze the reliability of aeroengine blades with the fatigue failure mode. Two types of TC4 alloy experiments are conducted for the study on the damage accumulation law. All the parameters in the nonlinear damage model are obtained by the tension–compression fatigue tests, and the accuracy of the nonlinear damage model is verified by the damage tests. The strength degeneration model is put forward on the basis of the Chaboche nonlinear damage theory and the Griffith fracture criterion, and determined by measuring the fatigue toughness during the tests. From the comparison of two kinds of degeneration models based on the Miner’s linear law and the nonlinear damage model respectively, the nonlinear model has a significant advantage on prediction accuracy especially in the later period of life. A time-dependent SSI reliability model is established. By computing the stress distribution using the finite element （FE） technique, the reliability of a single blade during the whole service life is obtained. Considering the failure correlation of components, a modified reliability model of aero-engine blades with common cause failure （CCF） is presented. It shows a closer and more reasonable process with the actual working condition. The improved reliability model is illustrated to be applied to aero-engine blades well, and the approach purposed in this paper is suitable for any actual machinery component of aero-engine rotor systems.
