Using a 20 L spherical explosion suppressing test system, the largest gas explosion pressure and maximum pressure rising rate with additives of ultra-fine ABC dry powder and diatomite powder were tested and compared, ...Using a 20 L spherical explosion suppressing test system, the largest gas explosion pressure and maximum pressure rising rate with additives of ultra-fine ABC dry powder and diatomite powder were tested and compared, and the explosion suppression effect of the two kinds of powder was analyzed. Experimental results show that both powders can suppress gas ex- plosion and ABC dry powder is superior to diatomite powder. Adding two powders under the same experimental conditions, when methane concentration is 7.0%, the maximum explosion pressure decreased 39% and 4%, respectively, while the rising rate of the maximum pressure decreased 80% and 53%, respectively. When methane concentration is 9.5%, the maximum ex- plosion pressure decreased 14% and 12%, respectively, the rising rate of maximum pressure decreased 62% and 27%, respec- tively, the maximum explosion pressure decreased 23% and 18%, respectively, while the rising rate of the maximum pressure decreased 77% and 70%, respectively. When methane concentration is 12.0%, the explosion suppression effect of ultra-fine ABC dry powder is not affected by the methane concentration, and the explosion suppression effect of diatomite powder under high methane concentrations is more obvious.展开更多
In this study, a flume experiment was designed to investigate the characteristics of wave-induced pore water pressure in the soil of a silty seabed with different clay contents, soil layer buried depths and wave heigh...In this study, a flume experiment was designed to investigate the characteristics of wave-induced pore water pressure in the soil of a silty seabed with different clay contents, soil layer buried depths and wave heights respectively. The study showed that water waves propagating over silty seabed can induce significant change of pore water pressure, and the amplitude of pore pressure depends on depth of buried soil layer, clay content and wave height, which are considered as the three influencing factors for pore water pressure change. The pressure will attenuate according to exponential law with increase of soil layer buried depth, and the attenuation being more rapid in those soil layers with higher clay content and greater wave height. The pore pressure in silty seabed increases rapidly in the initial stage of wave action, then decreases gradually to a stable value, depending on the depth of buried soil layer, clay content and wave height. The peak value of pore pressure will increase if clay content or depth of buried soil layer decreases, or wave height increases. The analysis indicated that these soils with 5% clay content and waves with higher wave height produce instability in bed easier, and that the wave energy is mostly dissipated near the surface of soils and 5% clay content in soils can prevent pore pressure from dissipating immediately.展开更多
This research describes a series of laboratory tests performed to characterize the mechanical properties of plastic concrete. The mechanical properties of plastic concrete are studied using a series of compression tes...This research describes a series of laboratory tests performed to characterize the mechanical properties of plastic concrete. The mechanical properties of plastic concrete are studied using a series of compression tests. Stress relaxation and controlled rate of loading tests are also performed to investigate the rate sensitivity and time-dependency of plastic concrete. An important requirement for the plastic concrete in such applications is adequate strength for the design loads. The replacement of cement content of plastic concrete by micro silica does not result in any significant decrease in workability of plastic concretes and hence, unlike the case for normal concretes, plasticizers or super plasticizers are not required to rectify the adverse effect of micro silica on workability. The aim of the experimental research was to investigate the effects of various levels of cement replacement by micro silica, including 0%, 3%, 6%, 9%, 12% and 15% on strength of plastic concrete. Obtained results show that the effect of micro silica on strength enhancement of plastic concretes is substantial and a replacement level of 15% resulted in 70%-180% increase in strength compared to the control mix. For normal concretes, the increase in strength due to incorporation of micro silica was generally reported as 30%-50%.展开更多
基金Supported by the Natural Science Foundation of China （50904049） the Development Fund Project of Xi＇an University of Science and Technology （2010047） the Shaanxi Provincial Scientific and Technological Fund （2010KJXX-08）
文摘Using a 20 L spherical explosion suppressing test system, the largest gas explosion pressure and maximum pressure rising rate with additives of ultra-fine ABC dry powder and diatomite powder were tested and compared, and the explosion suppression effect of the two kinds of powder was analyzed. Experimental results show that both powders can suppress gas ex- plosion and ABC dry powder is superior to diatomite powder. Adding two powders under the same experimental conditions, when methane concentration is 7.0%, the maximum explosion pressure decreased 39% and 4%, respectively, while the rising rate of the maximum pressure decreased 80% and 53%, respectively. When methane concentration is 9.5%, the maximum ex- plosion pressure decreased 14% and 12%, respectively, the rising rate of maximum pressure decreased 62% and 27%, respec- tively, the maximum explosion pressure decreased 23% and 18%, respectively, while the rising rate of the maximum pressure decreased 77% and 70%, respectively. When methane concentration is 12.0%, the explosion suppression effect of ultra-fine ABC dry powder is not affected by the methane concentration, and the explosion suppression effect of diatomite powder under high methane concentrations is more obvious.
基金financially supported by the National Fundamental Research Program of Ministry of Science & Technology,China (Grant No. 2010CB951202)
文摘In this study, a flume experiment was designed to investigate the characteristics of wave-induced pore water pressure in the soil of a silty seabed with different clay contents, soil layer buried depths and wave heights respectively. The study showed that water waves propagating over silty seabed can induce significant change of pore water pressure, and the amplitude of pore pressure depends on depth of buried soil layer, clay content and wave height, which are considered as the three influencing factors for pore water pressure change. The pressure will attenuate according to exponential law with increase of soil layer buried depth, and the attenuation being more rapid in those soil layers with higher clay content and greater wave height. The pore pressure in silty seabed increases rapidly in the initial stage of wave action, then decreases gradually to a stable value, depending on the depth of buried soil layer, clay content and wave height. The peak value of pore pressure will increase if clay content or depth of buried soil layer decreases, or wave height increases. The analysis indicated that these soils with 5% clay content and waves with higher wave height produce instability in bed easier, and that the wave energy is mostly dissipated near the surface of soils and 5% clay content in soils can prevent pore pressure from dissipating immediately.
文摘This research describes a series of laboratory tests performed to characterize the mechanical properties of plastic concrete. The mechanical properties of plastic concrete are studied using a series of compression tests. Stress relaxation and controlled rate of loading tests are also performed to investigate the rate sensitivity and time-dependency of plastic concrete. An important requirement for the plastic concrete in such applications is adequate strength for the design loads. The replacement of cement content of plastic concrete by micro silica does not result in any significant decrease in workability of plastic concretes and hence, unlike the case for normal concretes, plasticizers or super plasticizers are not required to rectify the adverse effect of micro silica on workability. The aim of the experimental research was to investigate the effects of various levels of cement replacement by micro silica, including 0%, 3%, 6%, 9%, 12% and 15% on strength of plastic concrete. Obtained results show that the effect of micro silica on strength enhancement of plastic concretes is substantial and a replacement level of 15% resulted in 70%-180% increase in strength compared to the control mix. For normal concretes, the increase in strength due to incorporation of micro silica was generally reported as 30%-50%.
