The Tangjiashan Quake Lake is the largest quake lake triggered by the 5.12 Wenchuan Earthquake that happened on May 12,2008 in China,posing high risk of catastrophic flash flood hazards to downstream human life and pr...The Tangjiashan Quake Lake is the largest quake lake triggered by the 5.12 Wenchuan Earthquake that happened on May 12,2008 in China,posing high risk of catastrophic flash flood hazards to downstream human life and properties.A physics-based numerical simulation approach is proposed for real-time prediction of dam breach development of the Tangjiashan Quake Lake in the case of emergency treatment.Bed erosion and lateral development of the dam breach are represented through accounting for the underlying physics including selective sediment transport and gravitational collapse.Conceptualized breach erosion model that involves few parameters enables quick calibration based on the monitored hydrological data in emergency analysis where fully geotechnical information about the barrier dam is not available.The process of dam breach development is found to be nonlinear in cascades due to the combined effects of headcutting and bank collapse.The agreement between the simulation results and the observed data shows the applicability of the present approach for emergency analysis of quake lakes.Limitations will arise in the situation where the soil composition of barrier dam is significantly inhomogeneous.Incorporation of circular arc failure for cohesive soil and lateral seepage in bank slope will also enhance its applicability to complex situations.展开更多
To investigate the mechanism of cavitation erosion caused by laser-induced single bubble near the surface coating alloy coating material, we utilized a nanosecond resolution photography system based on a Q-switched Nd...To investigate the mechanism of cavitation erosion caused by laser-induced single bubble near the surface coating alloy coating material, we utilized a nanosecond resolution photography system based on a Q-switched Nd: YAG laser and conventional industrial camera to carefully observe the transient process of bubble collapse under different conditions. We analyzed the generation of collapse microjets and the emission of collapse shock waves and explored the cavitation erosion characteristics caused by laser-induced single bubble collapse. We discovered that even on surfaces of highly hard and corrosion-resistant alloy coatings, severe cavitation erosion occurred, and there was a phenomenon of mismatch between the cavitation erosion location and the bubble projection position. The intensity of cavitation erosion depended on the energy self-focusing effect of the collapse shockwaves. In the experiments, we also observed the self-focusing phenomenon of collapse shockwaves under different conditions. The self-focusing effect of collapse shockwaves weakened as the distance between the bubble and the material surface increased, which may be the cause of cavitation erosion induced by a laser-induced single bubble.展开更多
China is experiencing conflicts between its large population and scarce arable land,and between a demand for high productivity and the severe soil erosion of arable land.Since 1949,China has committed to soil and wate...China is experiencing conflicts between its large population and scarce arable land,and between a demand for high productivity and the severe soil erosion of arable land.Since 1949,China has committed to soil and water conservation(SWC),for which eight regions and 41 subregions have been developed to improve the environment and increase land productivity.To obtain information from the regional planning and strategies for SWC and to explore whether SWC practices simultaneously contribute to soil conservation,ecosystem functioning,and the livelihoods of local farmers,and to summarize the successful experiences of various SWC paradigms with distinct characteristics and mechanisms of soil erosion,this paper systematically presents seven SWC regions(excluding the Tibetan Plateau region)and 14 typical SWC paradigms,focusing on erosion mechanisms and the key challenges or issues in the seven regions as well as on the core problems,main objectives,key technologies,and the performance of the 14 typical paradigms.In summary,the 14 typical SWC paradigms successfully prevent and control local soil erosion,and have largely enhanced,or at least do not harm,the livelihoods of local farmers.However,there remain many challenges and issues on SWC and socioeconomic development that need to be addressed in the seven SWC regions.China,thus,still has a long way to go in successfully gaining the win-win objective of SWC and human aspects of development.展开更多
基金Supported by the National Basic Research Program of China ("973") (Grant No.2007CB714100)the National Natural Science Foundation of China (Grant No.50849003)
文摘The Tangjiashan Quake Lake is the largest quake lake triggered by the 5.12 Wenchuan Earthquake that happened on May 12,2008 in China,posing high risk of catastrophic flash flood hazards to downstream human life and properties.A physics-based numerical simulation approach is proposed for real-time prediction of dam breach development of the Tangjiashan Quake Lake in the case of emergency treatment.Bed erosion and lateral development of the dam breach are represented through accounting for the underlying physics including selective sediment transport and gravitational collapse.Conceptualized breach erosion model that involves few parameters enables quick calibration based on the monitored hydrological data in emergency analysis where fully geotechnical information about the barrier dam is not available.The process of dam breach development is found to be nonlinear in cascades due to the combined effects of headcutting and bank collapse.The agreement between the simulation results and the observed data shows the applicability of the present approach for emergency analysis of quake lakes.Limitations will arise in the situation where the soil composition of barrier dam is significantly inhomogeneous.Incorporation of circular arc failure for cohesive soil and lateral seepage in bank slope will also enhance its applicability to complex situations.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52179092,52222904).
文摘To investigate the mechanism of cavitation erosion caused by laser-induced single bubble near the surface coating alloy coating material, we utilized a nanosecond resolution photography system based on a Q-switched Nd: YAG laser and conventional industrial camera to carefully observe the transient process of bubble collapse under different conditions. We analyzed the generation of collapse microjets and the emission of collapse shock waves and explored the cavitation erosion characteristics caused by laser-induced single bubble collapse. We discovered that even on surfaces of highly hard and corrosion-resistant alloy coatings, severe cavitation erosion occurred, and there was a phenomenon of mismatch between the cavitation erosion location and the bubble projection position. The intensity of cavitation erosion depended on the energy self-focusing effect of the collapse shockwaves. In the experiments, we also observed the self-focusing phenomenon of collapse shockwaves under different conditions. The self-focusing effect of collapse shockwaves weakened as the distance between the bubble and the material surface increased, which may be the cause of cavitation erosion induced by a laser-induced single bubble.
基金Under the auspices of Strategic Priority Program of the Chinese Academy of Sciences(CAS)(No.XDA20040200)the National Key Research and Development Program(No.2016YFC0501707)。
文摘China is experiencing conflicts between its large population and scarce arable land,and between a demand for high productivity and the severe soil erosion of arable land.Since 1949,China has committed to soil and water conservation(SWC),for which eight regions and 41 subregions have been developed to improve the environment and increase land productivity.To obtain information from the regional planning and strategies for SWC and to explore whether SWC practices simultaneously contribute to soil conservation,ecosystem functioning,and the livelihoods of local farmers,and to summarize the successful experiences of various SWC paradigms with distinct characteristics and mechanisms of soil erosion,this paper systematically presents seven SWC regions(excluding the Tibetan Plateau region)and 14 typical SWC paradigms,focusing on erosion mechanisms and the key challenges or issues in the seven regions as well as on the core problems,main objectives,key technologies,and the performance of the 14 typical paradigms.In summary,the 14 typical SWC paradigms successfully prevent and control local soil erosion,and have largely enhanced,or at least do not harm,the livelihoods of local farmers.However,there remain many challenges and issues on SWC and socioeconomic development that need to be addressed in the seven SWC regions.China,thus,still has a long way to go in successfully gaining the win-win objective of SWC and human aspects of development.
