Strength and deformation behaviors of rockfill materials,key factors for determining the stability of dams,pertain strongly to the grain crushing characteristics.In this study,single-particle crushing tests were carri...Strength and deformation behaviors of rockfill materials,key factors for determining the stability of dams,pertain strongly to the grain crushing characteristics.In this study,single-particle crushing tests were carried out on rockfill materials with nominal particle diameters of 2.5 mm,5 mm and 10 mm to investigate the particle size effect on the single-particle strength and the relationship between the characteristic stress and probability of non-failure.Test data were found to be described by the Weibull distribution with the Weibull modulus of 3.24.Assemblies with uniform nominal grains were then subjected to one-dimensional compression tests at eight levels of vertical stress with a maximum of 100 MPa.The yield stress in one-dimensional compression tests increased with decreasing the particle size,which could be estimated from the single-particle crushing tests.The void ratio-vertical stress curve could be predicted by an exponential function.The particle size distribution curve increased obviously with applied stresses less than 16 MPa and gradually reached the ultimate fractal grading.The relative breakage index became constant with stress up to 64 MPa and was obtained from the ultimate grading at the fractal dimension(a?2:7).A hyperbolical function was also found useful for describing the relationship between the relative breakage index and input work during one-dimensional compression tests.展开更多
Gangue from underground separation of coal can directly be used for filling mined out areas, saving transport capacity and reducing the amount of waste polluting the environment above the ground. We introduced a struc...Gangue from underground separation of coal can directly be used for filling mined out areas, saving transport capacity and reducing the amount of waste polluting the environment above the ground. We introduced a structure and operating principle of an underground direct-impact sieving device by which a separation experiment was carried out. By means of high speed conveyer belts, coal and gangue impacted the breaking board at high speeds ranging from 6 to 14 m/s. Given the differences of hardness between coal and gangue, after selective crushing, the gangue with the higher hardness was crushed less and coal with lower hardness crushed more, which could be separated by a 50 mm sieving plate. The material above the sieving plate was disposed of as gangue and the material below as coal. The results indicate that the crush ratio below the 50 mm sieving plate increases linearly with an increase in impact velocity and decays exponentially with an increase in hardness. Employing this equipment to separate coal and gangue, the hardness of coal f should be <2. This separation device provides relatively good effect in separating coal and gangue with a relatively wide difference of hardness.展开更多
Background Failure of balloon catheter passing through the occluded segment accounts for 10%-15% of all procedures during percutaneous coronary intervention （PCI） for chronic total occlusion （CTO）. We sought to in...Background Failure of balloon catheter passing through the occluded segment accounts for 10%-15% of all procedures during percutaneous coronary intervention （PCI） for chronic total occlusion （CTO）. We sought to investigate an original technique for facilitating balloon catheter passing by multi-wire plaque crushing. Methods Between July 2000 and October 2007, 152 patients with 164 CTO lesions who had failed balloon passing were treated by multi-wire plaque crushing technique. The main process of this technique was to insert 1 or 2 wires along with the original wire located in the true lumen of CTO lesions after balloon failure for plaque crushing and then to withdraw the crushing wires to get an enlarged lumen inside of the occlusion segment, thus facilitating the balloon passing. Results Both overall lesion and technique success rates were 91.5% （150/164）. A total of 211 crushing wires were used during. PCI, including 1 crushing wire for 117 （71.3%） lesions and 2 crushing wires for 47 （28.7%） lesions. Approximately 57.3% （121/211） of all crushing wires were those already used in the same procedure. Technique failure occurred in 14 lesions （8.5%）. Technique failure was due to crushing wires entering false lumen （92.9%, 13/14） and coronary perforation （7.1%, 1/14）. Major procedural complications included coronary perforation （1 case） and severe coronary dissection （2 cases）, all of which were successfully treated. Conclusions Multi-wire plaque crushing technique is effective in facilitating balloon catheter passing during CTO PCI. It is feasible, economical and relatively safe with a low rate of procedural complications.展开更多
Global helium(He) shortage is a challenging problem;however, the types of helium source rock and the mechanisms of He generation and release therein remain still poorly understood. In this study, in order to evaluate ...Global helium(He) shortage is a challenging problem;however, the types of helium source rock and the mechanisms of He generation and release therein remain still poorly understood. In this study, in order to evaluate the potential of granite as an effective helium source rock, we collected granitic samples from the North Qinling Orogen, Central China, in the south of the helium-rich Weihe Basin. The helium generation and release behaviors in granite were studied through analysis of U and Th concentrations, EMPA images, and He and Ar concentrations and isotopic ratios extracted by crushing and stepwise heating. The results indicate that Ar has a better retention and a lower mobility than He. 3 He/4 He ratios released by crushing and stepwise heating are 0.016–0.056 RA and 0.003–0.572 RA, respectively, where RA is the atmospheric 3 He/4 He of 1.4×10-6, reflecting a crustal and radiogenic source. Helium concentrations extracted by the two ways are 0.13–0.95 ucm3 STP/g and 7.82–115.62 ucm3 STP/g, respectively, suggesting that matrix-sited He accounts for more than 98% of total helium preserved in granite. In addition, the total generated He amounts in granites are calculated based on the measured U and Th concentrations in granitic samples. Dividing the preserved He quantities by the generated He amounts, it turned out that less than 10% of He produced since the formation of the granite is preserved in the rock over geological time, suggesting that more than 90% generated He can be transferred to the Weihe Basin. Temperature and fracture are the two critical factors controlling He release. Based on the relationship between He diffusivity of granites and temperature and the He closure temperatures of a variety of U-and Th-rich minerals(27–250°C), we estimate that He can be partially released out of granite at the depths <400 m and totally released at the depths >7800 m. Fractures provide effective transfer of free He from deep source rocks to shallow reservoirs. Finally, a model on granite as an effective 展开更多
基金financial support from the 111 Project (Grant No. B13024)the National Science Foundation of China (Grant Nos. 51509024, 51678094 and 51578096)+2 种基金the Fundamental Research Funds for the Central Universities (Grant No. 106112017CDJQJ208848)the Special Financial Grant from the China Postdoctoral Science Foundation (Grant No. 2017T100681)the State Key Laboratory for Geo Mechanics and Deep Underground Engineering, China University of Mining and Technology (Grant No. SKLGDUEK1810)
文摘Strength and deformation behaviors of rockfill materials,key factors for determining the stability of dams,pertain strongly to the grain crushing characteristics.In this study,single-particle crushing tests were carried out on rockfill materials with nominal particle diameters of 2.5 mm,5 mm and 10 mm to investigate the particle size effect on the single-particle strength and the relationship between the characteristic stress and probability of non-failure.Test data were found to be described by the Weibull distribution with the Weibull modulus of 3.24.Assemblies with uniform nominal grains were then subjected to one-dimensional compression tests at eight levels of vertical stress with a maximum of 100 MPa.The yield stress in one-dimensional compression tests increased with decreasing the particle size,which could be estimated from the single-particle crushing tests.The void ratio-vertical stress curve could be predicted by an exponential function.The particle size distribution curve increased obviously with applied stresses less than 16 MPa and gradually reached the ultimate fractal grading.The relative breakage index became constant with stress up to 64 MPa and was obtained from the ultimate grading at the fractal dimension(a?2:7).A hyperbolical function was also found useful for describing the relationship between the relative breakage index and input work during one-dimensional compression tests.
基金the Natural Science Foundation of Jiangsu Province (No.BK2009098)
文摘Gangue from underground separation of coal can directly be used for filling mined out areas, saving transport capacity and reducing the amount of waste polluting the environment above the ground. We introduced a structure and operating principle of an underground direct-impact sieving device by which a separation experiment was carried out. By means of high speed conveyer belts, coal and gangue impacted the breaking board at high speeds ranging from 6 to 14 m/s. Given the differences of hardness between coal and gangue, after selective crushing, the gangue with the higher hardness was crushed less and coal with lower hardness crushed more, which could be separated by a 50 mm sieving plate. The material above the sieving plate was disposed of as gangue and the material below as coal. The results indicate that the crush ratio below the 50 mm sieving plate increases linearly with an increase in impact velocity and decays exponentially with an increase in hardness. Employing this equipment to separate coal and gangue, the hardness of coal f should be <2. This separation device provides relatively good effect in separating coal and gangue with a relatively wide difference of hardness.
文摘Background Failure of balloon catheter passing through the occluded segment accounts for 10%-15% of all procedures during percutaneous coronary intervention （PCI） for chronic total occlusion （CTO）. We sought to investigate an original technique for facilitating balloon catheter passing by multi-wire plaque crushing. Methods Between July 2000 and October 2007, 152 patients with 164 CTO lesions who had failed balloon passing were treated by multi-wire plaque crushing technique. The main process of this technique was to insert 1 or 2 wires along with the original wire located in the true lumen of CTO lesions after balloon failure for plaque crushing and then to withdraw the crushing wires to get an enlarged lumen inside of the occlusion segment, thus facilitating the balloon passing. Results Both overall lesion and technique success rates were 91.5% （150/164）. A total of 211 crushing wires were used during. PCI, including 1 crushing wire for 117 （71.3%） lesions and 2 crushing wires for 47 （28.7%） lesions. Approximately 57.3% （121/211） of all crushing wires were those already used in the same procedure. Technique failure occurred in 14 lesions （8.5%）. Technique failure was due to crushing wires entering false lumen （92.9%, 13/14） and coronary perforation （7.1%, 1/14）. Major procedural complications included coronary perforation （1 case） and severe coronary dissection （2 cases）, all of which were successfully treated. Conclusions Multi-wire plaque crushing technique is effective in facilitating balloon catheter passing during CTO PCI. It is feasible, economical and relatively safe with a low rate of procedural complications.
基金supported by the National Science Foundation of China(NSFC,No.41572131)the China Geology Survey(DD20190103).
文摘Global helium(He) shortage is a challenging problem;however, the types of helium source rock and the mechanisms of He generation and release therein remain still poorly understood. In this study, in order to evaluate the potential of granite as an effective helium source rock, we collected granitic samples from the North Qinling Orogen, Central China, in the south of the helium-rich Weihe Basin. The helium generation and release behaviors in granite were studied through analysis of U and Th concentrations, EMPA images, and He and Ar concentrations and isotopic ratios extracted by crushing and stepwise heating. The results indicate that Ar has a better retention and a lower mobility than He. 3 He/4 He ratios released by crushing and stepwise heating are 0.016–0.056 RA and 0.003–0.572 RA, respectively, where RA is the atmospheric 3 He/4 He of 1.4×10-6, reflecting a crustal and radiogenic source. Helium concentrations extracted by the two ways are 0.13–0.95 ucm3 STP/g and 7.82–115.62 ucm3 STP/g, respectively, suggesting that matrix-sited He accounts for more than 98% of total helium preserved in granite. In addition, the total generated He amounts in granites are calculated based on the measured U and Th concentrations in granitic samples. Dividing the preserved He quantities by the generated He amounts, it turned out that less than 10% of He produced since the formation of the granite is preserved in the rock over geological time, suggesting that more than 90% generated He can be transferred to the Weihe Basin. Temperature and fracture are the two critical factors controlling He release. Based on the relationship between He diffusivity of granites and temperature and the He closure temperatures of a variety of U-and Th-rich minerals(27–250°C), we estimate that He can be partially released out of granite at the depths <400 m and totally released at the depths >7800 m. Fractures provide effective transfer of free He from deep source rocks to shallow reservoirs. Finally, a model on granite as an effective
