When the traditional drill and blast method is applied to rock crushing projects,it has strong vibration,loud noise and dust pollution,so it cannot be used in densely populated areas such as urban public works.We deve...When the traditional drill and blast method is applied to rock crushing projects,it has strong vibration,loud noise and dust pollution,so it cannot be used in densely populated areas such as urban public works.We developed a supercritical CO_(2)true triaxial pneumatic rock-breaking experimental system,and conducted laboratory and field tests of dry ice powder pneumatic rock-breaking.The characteristics of the blast-induced vibration velocity waveform and the evolution of the vibration velocity and frequency with the focal distance were analyzed and discussed.The fracturing mechanism of dry ice powder pneumatic rock breaking is studied.The research results show that:(1)The vibration velocity induced by dry ice powder pneumatic rock breaking decays as a power function with the increase of the focal distance;(2)The vibration frequency caused by dry ice powder pneumatic rock breaking is mainly distributed in 1–120 Hz.Due to the dispersion effect,the dominant frequency of 10–30 Hz appears abnormally attenuated;(3)The traditional CO_(2)phase change fracturing energy calculation formula is also applicable to dry ice pneumatic rock breaking technology,and the trinitrotoluene(TNT)equivalent of fracturing energy is applicable to the Sadovsky formula;(4)Dry ice powder pneumatic rock breaking is shock wave and highenergy gas acting together to fracture rock,which can be divided into three stages,among which the gas wedge action of high-energy gas plays a dominant role in rock mass damage.展开更多
A ship-ice-water interaction model is established using smoothed-particle hydrodynamics(SPH)to predict the ice breaking resistance of the icebreaker in the Yellow River effectively.This method includes the numerical p...A ship-ice-water interaction model is established using smoothed-particle hydrodynamics(SPH)to predict the ice breaking resistance of the icebreaker in the Yellow River effectively.This method includes the numerical process of the constitutive equation,yield criterion,and the coupling model in SPH.The ice breaking resistance is determined under different conditions.The numerical results of the ice breaking resistance agree with the empirical formula results.Results show that the prediction accuracy of ice resistance is less than 17.6%compared with the empirical formula in the level ice.The method can also be extended to predict the floe motion and ice breaking resistance in actual river channels.The validation against the empirical formula indicates that the proposed ship-ice-water SPH method can predict the ice breaking resistance of icebreakers in actual rivers effectively.The predicted ice breaking resistance is analyzed under different conditions.The ice breaking resistance increases with increasing bending strength and ice thickness,and the latter is the most important factor influencing ice resistance.展开更多
A lot of tests on ice forces on vertical cylindrical piles are conducted in the ice basin of ice laboratory in Tianjin University to identify the characteristics of ice forces on fixed platforms in the Bohai Gulf. A f...A lot of tests on ice forces on vertical cylindrical piles are conducted in the ice basin of ice laboratory in Tianjin University to identify the characteristics of ice forces on fixed platforms in the Bohai Gulf. A function of ice forces is simplified on basis of test data, and the characteristics of the ice forces including the amplitude of the force and the breaking frequency of the ice sheet is detailed by use of the Fast-Fourier-Transform method, The results show that the ice breaking frequency presents a linear relationship with the ratio of ice moving velocity to ice thickness at low velocities. At high velocities, the frequency remains constant with the increase of the ratio of ice moving velocity to ice thickness. These conclusions are compared those published in literature.展开更多
Swan Lake on Ice, a show which integrates figure skating with ballet and is produced by the Imperial Ice Stars, the world＇s leading theatrical ice skating company, was staged at the Tianqiao Performing Arts Center in...Swan Lake on Ice, a show which integrates figure skating with ballet and is produced by the Imperial Ice Stars, the world＇s leading theatrical ice skating company, was staged at the Tianqiao Performing Arts Center in Beijing from August 15 to 19.展开更多
基金supported by the State Key Laboratory Open Fund(No.HKLBEF202004)the Natural Science Foundation of Jiangsu Province(No.BK20201313)+2 种基金the Key Program of National Natural Science Foundation of China(No.51934007)the Major Scientific and Technological Innovation Program in Shandong Province(No.2019JZZY020505)the National Key Research and Development Program of China(No.2022YFC3004700)。
文摘When the traditional drill and blast method is applied to rock crushing projects,it has strong vibration,loud noise and dust pollution,so it cannot be used in densely populated areas such as urban public works.We developed a supercritical CO_(2)true triaxial pneumatic rock-breaking experimental system,and conducted laboratory and field tests of dry ice powder pneumatic rock-breaking.The characteristics of the blast-induced vibration velocity waveform and the evolution of the vibration velocity and frequency with the focal distance were analyzed and discussed.The fracturing mechanism of dry ice powder pneumatic rock breaking is studied.The research results show that:(1)The vibration velocity induced by dry ice powder pneumatic rock breaking decays as a power function with the increase of the focal distance;(2)The vibration frequency caused by dry ice powder pneumatic rock breaking is mainly distributed in 1–120 Hz.Due to the dispersion effect,the dominant frequency of 10–30 Hz appears abnormally attenuated;(3)The traditional CO_(2)phase change fracturing energy calculation formula is also applicable to dry ice pneumatic rock breaking technology,and the trinitrotoluene(TNT)equivalent of fracturing energy is applicable to the Sadovsky formula;(4)Dry ice powder pneumatic rock breaking is shock wave and highenergy gas acting together to fracture rock,which can be divided into three stages,among which the gas wedge action of high-energy gas plays a dominant role in rock mass damage.
基金Supported by the National Key Research and Development Program of China(No.2018YFC1508405)National Natural Science Foundation of China(Nos.51879051 and 51739001)+1 种基金the Open Fund of the Key Laboratory of Far-shore Wind Power Technology of Zhejiang Province(ZOE20200007)Natural Science Foundation of Heilongjiang Province in China(LH2020E071).
文摘A ship-ice-water interaction model is established using smoothed-particle hydrodynamics(SPH)to predict the ice breaking resistance of the icebreaker in the Yellow River effectively.This method includes the numerical process of the constitutive equation,yield criterion,and the coupling model in SPH.The ice breaking resistance is determined under different conditions.The numerical results of the ice breaking resistance agree with the empirical formula results.Results show that the prediction accuracy of ice resistance is less than 17.6%compared with the empirical formula in the level ice.The method can also be extended to predict the floe motion and ice breaking resistance in actual river channels.The validation against the empirical formula indicates that the proposed ship-ice-water SPH method can predict the ice breaking resistance of icebreakers in actual rivers effectively.The predicted ice breaking resistance is analyzed under different conditions.The ice breaking resistance increases with increasing bending strength and ice thickness,and the latter is the most important factor influencing ice resistance.
基金This project is financially supported by the National Natural Science Foundation of China (Grant No. 59739170)
文摘A lot of tests on ice forces on vertical cylindrical piles are conducted in the ice basin of ice laboratory in Tianjin University to identify the characteristics of ice forces on fixed platforms in the Bohai Gulf. A function of ice forces is simplified on basis of test data, and the characteristics of the ice forces including the amplitude of the force and the breaking frequency of the ice sheet is detailed by use of the Fast-Fourier-Transform method, The results show that the ice breaking frequency presents a linear relationship with the ratio of ice moving velocity to ice thickness at low velocities. At high velocities, the frequency remains constant with the increase of the ratio of ice moving velocity to ice thickness. These conclusions are compared those published in literature.
文摘Swan Lake on Ice, a show which integrates figure skating with ballet and is produced by the Imperial Ice Stars, the world＇s leading theatrical ice skating company, was staged at the Tianqiao Performing Arts Center in Beijing from August 15 to 19.
