The state of clean sand was mainly dependent on its void ratio(density)and confining stress that greatly influenced the mechanical behavior(compression,dilatancy and liquefaction)of clean sand.Confirming whether the c...The state of clean sand was mainly dependent on its void ratio(density)and confining stress that greatly influenced the mechanical behavior(compression,dilatancy and liquefaction)of clean sand.Confirming whether the confining stress was a state variable of sand required precise element tests at different confining stress,especially the tests under very low confining stress whose test data were very limited.In this study,static-dynamic characteristics of clean sand was comprehensively investigated by a unified test program under low and normal confining stress ranging from 5 to 98 kPa,under monotonic/cyclic and drained/undrained conditions,together with the literature available data under confining stress of 1.0 to 3.0 MPa.For monotonic loading tests,the contraction/dilation phase transition was observed for loose sand at low confining stress,and dilatancy angles were stress-dependent.In addition,the liquefaction resistance was observed to increase with reducing of confining stress,and the axial strain varied from compressive to dilative when confining stress increased.Special attention was also paid to the enhancement effect of membrane,and it was observed that its influence on the test results was limited.In addition,the experimental results were proved reliable by reproducibility.展开更多
Plant carbon sequestration is an effective way to abate the global warming. However, the field-scale carbon exchange on a peach orchard remains unclear. Here, using an eddy covariance technique, the net ecosystem carb...Plant carbon sequestration is an effective way to abate the global warming. However, the field-scale carbon exchange on a peach orchard remains unclear. Here, using an eddy covariance technique, the net ecosystem carbon dioxide exchange and energy balance were analyzed on a coarse-sand-field, no-tillage, 12-year-old-peach orchard. The results showed that during full flowering, the ability to sequestrate carbon was significant, it reached on the peak of-0.33 mg （CO2） m^-2 s^-1. During rapid growth, the Bowen ratio was under 0.3 and daily net carbon sequestration reached on the peak of-25.1 g （CO2） m^-2 d^-1. During the leaf fall stage, there is a great deal of CO2 emissions, the peak value of carbon sequestration reached ＋0.60 mg （CO2） m^-2 s^-1. During monitoring period, the daily average of net carbon sequestration and Bowen ratio was 1.22 ± 1.56 and -2.90 ± 6.63 g （CO2） m^-2 d^-1, respectively. The net carbon sequestration could reach -1,052 g （CO2） m^-2 in a year. These results reveal that there is high carbon sequestration on a coarse-sand-field, no-tillage peach orchard.展开更多
基金Projects(51908288,41627801)supported by the National Natural Science Foundation of China。
文摘The state of clean sand was mainly dependent on its void ratio(density)and confining stress that greatly influenced the mechanical behavior(compression,dilatancy and liquefaction)of clean sand.Confirming whether the confining stress was a state variable of sand required precise element tests at different confining stress,especially the tests under very low confining stress whose test data were very limited.In this study,static-dynamic characteristics of clean sand was comprehensively investigated by a unified test program under low and normal confining stress ranging from 5 to 98 kPa,under monotonic/cyclic and drained/undrained conditions,together with the literature available data under confining stress of 1.0 to 3.0 MPa.For monotonic loading tests,the contraction/dilation phase transition was observed for loose sand at low confining stress,and dilatancy angles were stress-dependent.In addition,the liquefaction resistance was observed to increase with reducing of confining stress,and the axial strain varied from compressive to dilative when confining stress increased.Special attention was also paid to the enhancement effect of membrane,and it was observed that its influence on the test results was limited.In addition,the experimental results were proved reliable by reproducibility.
基金This work was supported by National Key Technology Supported Program of China （Project 2008BAD95B07, 2011BAD32B03）, the China National Natural Science Foundation （Project 31040006）.
文摘Plant carbon sequestration is an effective way to abate the global warming. However, the field-scale carbon exchange on a peach orchard remains unclear. Here, using an eddy covariance technique, the net ecosystem carbon dioxide exchange and energy balance were analyzed on a coarse-sand-field, no-tillage, 12-year-old-peach orchard. The results showed that during full flowering, the ability to sequestrate carbon was significant, it reached on the peak of-0.33 mg （CO2） m^-2 s^-1. During rapid growth, the Bowen ratio was under 0.3 and daily net carbon sequestration reached on the peak of-25.1 g （CO2） m^-2 d^-1. During the leaf fall stage, there is a great deal of CO2 emissions, the peak value of carbon sequestration reached ＋0.60 mg （CO2） m^-2 s^-1. During monitoring period, the daily average of net carbon sequestration and Bowen ratio was 1.22 ± 1.56 and -2.90 ± 6.63 g （CO2） m^-2 d^-1, respectively. The net carbon sequestration could reach -1,052 g （CO2） m^-2 in a year. These results reveal that there is high carbon sequestration on a coarse-sand-field, no-tillage peach orchard.
