The fiber reinforced concrete has good dynamic mechanical properties. But corresponding research lacks the dynamic damage characteristics of the polypropylene fiber（fiber of low elastic modulus） and steel fiber（fib...The fiber reinforced concrete has good dynamic mechanical properties. But corresponding research lacks the dynamic damage characteristics of the polypropylene fiber（fiber of low elastic modulus） and steel fiber（fiber of high elastic modulus） reinforced concrete under medium strain rate（10-6 s-1-10-4 s-1）. In order to study the effect of strain rate on the damage characteristics of fiber reinforced concrete during the full curve damage process, the real time dynamic acoustic emission（AE） technique was applied to monitor the damage process of fiber reinforced concrete at three strain rates. The AE wavelet energy spectrum in ca8 frequency band and average AE peak frequency at three strain rates were analyzed. With the accumulation of damage, the AE wavelet energy spectrum in ca8 frequency band increased first and then decreased, and the average AE peak frequency increased gradually. With the increase of strain rate, the AE wavelet energy spectrum in ca8 frequency band and average AE peak frequency decreased gradually. The polypropylene fiber content has more obvious effect on the Dynamic increase factor（DIF） of the peak stress than the steel fiber content. The theoretical basis was provided for the monitoring of dynamic damage of fiber reinforced concrete based on the AE technique.展开更多
The Shenhu area is one of the promise target areas for marine gas hydrate exploration in the northern margin of the South China Sea.Pore water samples were collected from two piston cores (8.75 and 8.52 m) in site HS-...The Shenhu area is one of the promise target areas for marine gas hydrate exploration in the northern margin of the South China Sea.Pore water samples were collected from two piston cores (8.75 and 8.52 m) in site HS-A and site HS-B in the Shenhu area,and their major anion and cation contents and trace element contents have been analyzed in this study.Cl- concentrations in pore waters are similar to the seawater value and no systematic change along depth profiles has been found for the Cl- content in both sites.In site HS-A,the SO 2- 4 contents show a limited range in pore waters from 0 to 3 m depths,but a dramatic decrease is documented in depth below 3 m.Other elements such as Ca 2+,Mg 2+ and Sr 2+ show similar variation patterns as the SO 2- 4,i.e.,no variation in 0-3 m,but large decrease in depth below 3 m.In site HS-B,both the SO 4 and Ca 2+,Mg 2+ and Sr 2+ display a decrease pattern along the depth profile,but in 0-3 m the variation is less significant than those in depth below 3 m.In both sites HS-A and HS-B,I contents show a dramatic increase along depth profiles.Calculations show that the SMI depths are very shallow (10 and 11 m) in both sites,and the sulfate flux and I flux are very high.These geochemical characteristics and anomalies at Shenhu are quite similar to those found in other gas hydrate locations in the world,and a genetic link is suggested to be related to the gas hydrate occurrence at depths in the study area.In summary,we suggest that combined geochemical parameters in shallow sediment pore waters are useful indicators to indicate the gas hydrate occurrence at depths.展开更多
The Qiongdongnan Basin is one of the target areas for marine gas hydrate exploration in the northern margin of the South China Sea. In this study, major anion (e.g., SO42 , Cl, Br, I), cation (e.g., Ca, Mg, K, Na), an...The Qiongdongnan Basin is one of the target areas for marine gas hydrate exploration in the northern margin of the South China Sea. In this study, major anion (e.g., SO42 , Cl, Br, I), cation (e.g., Ca, Mg, K, Na), and trace element (e.g., Sr, Ba) con- centrations of pore water samples collected from site HQ-1PC in the Qiongdongnan Basin were analyzed. These geochemical data suggest that the process of AOM (Anaerobic Oxidation of Methane) is dominant in sulfate-reduction zone in this site due to high upwelling iodine flux and strong microbial activities. The iodine-rich fluids, which may carry methane for the gas hydrate formation, pass through the gas hydrate stability zone, mix with brine released during gas hydrate formation, and cause the geochemical anomalies observed at site HQ-1PC. The pore water geochemical characteristics and anomalies in the Qiongdongnan Basin are quite similar to those found in other gas hydrate locations in the Shenhu area in the northern South China Sea, and a genetic link is suggested with the possibility of gas hydrate occurrence in the study area.展开更多
基金Funded by the National Natural Science Foundation of China(No.51009058)Postdoctoral Science Foundation of China(No.2011M501160)+1 种基金the University Natural Science Research Project of Jiangsu Province(No.13KJD560002)the Doctoral Research Start-up Fund of Jinling Institute of Technology(No.Jit-b-201321)
文摘The fiber reinforced concrete has good dynamic mechanical properties. But corresponding research lacks the dynamic damage characteristics of the polypropylene fiber（fiber of low elastic modulus） and steel fiber（fiber of high elastic modulus） reinforced concrete under medium strain rate（10-6 s-1-10-4 s-1）. In order to study the effect of strain rate on the damage characteristics of fiber reinforced concrete during the full curve damage process, the real time dynamic acoustic emission（AE） technique was applied to monitor the damage process of fiber reinforced concrete at three strain rates. The AE wavelet energy spectrum in ca8 frequency band and average AE peak frequency at three strain rates were analyzed. With the accumulation of damage, the AE wavelet energy spectrum in ca8 frequency band increased first and then decreased, and the average AE peak frequency increased gradually. With the increase of strain rate, the AE wavelet energy spectrum in ca8 frequency band and average AE peak frequency decreased gradually. The polypropylene fiber content has more obvious effect on the Dynamic increase factor（DIF） of the peak stress than the steel fiber content. The theoretical basis was provided for the monitoring of dynamic damage of fiber reinforced concrete based on the AE technique.
基金supported by National Natural Science Foundation of China (Grant No.40773029)National Basic Research Program of China (Grant No.2009CB219506)Key Scientific Project from China Geological Survey (Grant No.GZHZ200203-04-02)
文摘The Shenhu area is one of the promise target areas for marine gas hydrate exploration in the northern margin of the South China Sea.Pore water samples were collected from two piston cores (8.75 and 8.52 m) in site HS-A and site HS-B in the Shenhu area,and their major anion and cation contents and trace element contents have been analyzed in this study.Cl- concentrations in pore waters are similar to the seawater value and no systematic change along depth profiles has been found for the Cl- content in both sites.In site HS-A,the SO 2- 4 contents show a limited range in pore waters from 0 to 3 m depths,but a dramatic decrease is documented in depth below 3 m.Other elements such as Ca 2+,Mg 2+ and Sr 2+ show similar variation patterns as the SO 2- 4,i.e.,no variation in 0-3 m,but large decrease in depth below 3 m.In site HS-B,both the SO 4 and Ca 2+,Mg 2+ and Sr 2+ display a decrease pattern along the depth profile,but in 0-3 m the variation is less significant than those in depth below 3 m.In both sites HS-A and HS-B,I contents show a dramatic increase along depth profiles.Calculations show that the SMI depths are very shallow (10 and 11 m) in both sites,and the sulfate flux and I flux are very high.These geochemical characteristics and anomalies at Shenhu are quite similar to those found in other gas hydrate locations in the world,and a genetic link is suggested to be related to the gas hydrate occurrence at depths in the study area.In summary,we suggest that combined geochemical parameters in shallow sediment pore waters are useful indicators to indicate the gas hydrate occurrence at depths.
基金supported by the National Basic Research Program of China (Grant No. 2009CB219506)National Natural Science Foundation of China (Grant Nos. 40773029, 40903002 and 40772073)Research Fund for the Doctoral Program of Higher Education of China (Grant No.20090091120046)
文摘The Qiongdongnan Basin is one of the target areas for marine gas hydrate exploration in the northern margin of the South China Sea. In this study, major anion (e.g., SO42 , Cl, Br, I), cation (e.g., Ca, Mg, K, Na), and trace element (e.g., Sr, Ba) con- centrations of pore water samples collected from site HQ-1PC in the Qiongdongnan Basin were analyzed. These geochemical data suggest that the process of AOM (Anaerobic Oxidation of Methane) is dominant in sulfate-reduction zone in this site due to high upwelling iodine flux and strong microbial activities. The iodine-rich fluids, which may carry methane for the gas hydrate formation, pass through the gas hydrate stability zone, mix with brine released during gas hydrate formation, and cause the geochemical anomalies observed at site HQ-1PC. The pore water geochemical characteristics and anomalies in the Qiongdongnan Basin are quite similar to those found in other gas hydrate locations in the Shenhu area in the northern South China Sea, and a genetic link is suggested with the possibility of gas hydrate occurrence in the study area.
基金Supported by the National Natural Science Foundation of China(31770102)Tianjin Manicipal Science and Technology Bureau(21JCQNJC00110)+1 种基金Tianjin Manicipal Health Commission(KJ20070)Chun Foundation of Tianjin First Central Hospital(2020CM12)。
