A simple formula is proposed to predict the vertical distribution of a suspended load concentration in a 2D steady turbulent flow. The proposed formula significantly improves the well-known Rouse formula where sedimen...A simple formula is proposed to predict the vertical distribution of a suspended load concentration in a 2D steady turbulent flow. The proposed formula significantly improves the well-known Rouse formula where sediment concentration has an infinitely large value at the channel bottom and a zero value at the water surface. Based on this formula and the logarithmic ve- locity profile, a theoretical elementary function for the transport rate of a suspended load is developed. This equation improves the Einstein equation in which the unit-width suspended sediment discharge must be solved by numerical integration and a contra- diction between the lower limit of the integral and that of velocity distribution exists.展开更多
Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical...Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical properties of the gravelly soils are affected by the content of coarse grain, fine particles, and their adhesive states. These Properties can be verified by laboratory unconsolidated undrained triaxial tests with grain size less than 5 mm and by large scale direct-shear tests with original grain content. Fine particles of the loose gravelly slopes are released under rainfalls, alternated the structures and mechanical properties, even affected the slope stability. There are a series of large scale direct-shear tests with different coarse grain contents to study the influence of fine particles releasing and migration, results showed the strength behavior of the gravelly soils were affected by the coarse grain content （5） and the inflection coarse grain contents. In order to study the erosion features of the gravelly soil slopes on rainfall conditions and the slopes stability alteration, we had carried out one sort of artificial rainfall local and model experiments, the runoff sediment contents were monitored during the experiments. Result showed that the shapes of the slopes surface transformed periodically, runoff sediment contents were divided into five phases according to the experiment phenomena, runoff sediment contents maintained downtrend during the rain time and the downtrend was obviouslyinterpreted by one descend belt no matter the rainfall intensity and the slope angels. Particle size analysis released the deposit on the slope surface lost almost all of the clay, most of the silt and sand after the experiments, this meant the fine particles releasing, migration and accumulation process on condition of rainfall resulted in the instability factor of the slopes even induced landslide or debris flow.展开更多
In order to understand and master the dynamic characteristics of sandy soil with different silt contents, the authors carried out many indoor dynamic triaxial tests for five groups of sandy with silt which took from P...In order to understand and master the dynamic characteristics of sandy soil with different silt contents, the authors carried out many indoor dynamic triaxial tests for five groups of sandy with silt which took from Panjin and Xiamen. Under the conditions of consolidation pressure of 100 kPa, 200 kPa, 300 kPa, stationary vibration frequency H=1 and cyclic loading, the authors found that the effective cohesion increases and the effective internal friction angle decreases with the increase of the silt contents. During the liquefied scope, the cementation and the strength have been increased with the increase of the silt contents.展开更多
Tropical peat swamp forest beds that have been reclaimed for agricultural use are generally an active source of nitrous oxide （N2O） efflux, however, the mechanism by which reclaimed tropical peat soils promote the e...Tropical peat swamp forest beds that have been reclaimed for agricultural use are generally an active source of nitrous oxide （N2O） efflux, however, the mechanism by which reclaimed tropical peat soils promote the emergence of N2O emitters in soil microbial communities remains unclear. The purpose of this study was to reveal the vertical distribution of N2O emission potential and its correlation with mineral nitrogen contents in reclaimed soils. Using a culture-based N2O emission assay, the N2O emission potentials of soil at various depths （0-450 cm） were investigated in two oil palm plantations in Sarawak, Malaysia, which had elapsed times of two years （E2Y） and 10 years （El 0Y） after deforestation, respectively. On the basis of the relationship between the vertical profiles of N2O emission potentials and the contents of mineralized nitrogen in the peat soils at various depths, the impact of land management on soil microbial communities was discussed. The peat soil at plantation site E2Y showed a trend of high N2O production in deep layers （200-400 cm）, whereas the older plantation site E10Y showed considerably more active N2O emission in shallow soil （10-50 cm）. N2O emission potentials among the soil microbial communities at different soil depths at the E10Y site showed positive correlations with NO3- and NH4＋ contents, whereas, soils obtained from the E2Y site had N2O emission potentials that were inversely proportional to the contents of NO3-. This contrasting vertical correlation between N2O-emitting potentials and mineralized nitrogen contents in bulk soils suggests that active N2O emission in deep soil at the E2Y site has maintained the original carbon-nitrogen （C/N） ratio of the peat soil, whereas at EIOY, such a regulatory system has been lost due to advanced soil degradation, leading to dynamic changes in the nitrogen cycle in shallow soil.展开更多
基金Project (Nos. 50079025 and 40231017) supported by the National Natural Science Foundation of China
文摘A simple formula is proposed to predict the vertical distribution of a suspended load concentration in a 2D steady turbulent flow. The proposed formula significantly improves the well-known Rouse formula where sediment concentration has an infinitely large value at the channel bottom and a zero value at the water surface. Based on this formula and the logarithmic ve- locity profile, a theoretical elementary function for the transport rate of a suspended load is developed. This equation improves the Einstein equation in which the unit-width suspended sediment discharge must be solved by numerical integration and a contra- diction between the lower limit of the integral and that of velocity distribution exists.
基金financially supported by National Natural Science Foundation of China (Grant Nos. 41172283, 41372313)National Basic Research Program of China (2012CB026103)
文摘Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical properties of the gravelly soils are affected by the content of coarse grain, fine particles, and their adhesive states. These Properties can be verified by laboratory unconsolidated undrained triaxial tests with grain size less than 5 mm and by large scale direct-shear tests with original grain content. Fine particles of the loose gravelly slopes are released under rainfalls, alternated the structures and mechanical properties, even affected the slope stability. There are a series of large scale direct-shear tests with different coarse grain contents to study the influence of fine particles releasing and migration, results showed the strength behavior of the gravelly soils were affected by the coarse grain content （5） and the inflection coarse grain contents. In order to study the erosion features of the gravelly soil slopes on rainfall conditions and the slopes stability alteration, we had carried out one sort of artificial rainfall local and model experiments, the runoff sediment contents were monitored during the experiments. Result showed that the shapes of the slopes surface transformed periodically, runoff sediment contents were divided into five phases according to the experiment phenomena, runoff sediment contents maintained downtrend during the rain time and the downtrend was obviouslyinterpreted by one descend belt no matter the rainfall intensity and the slope angels. Particle size analysis released the deposit on the slope surface lost almost all of the clay, most of the silt and sand after the experiments, this meant the fine particles releasing, migration and accumulation process on condition of rainfall resulted in the instability factor of the slopes even induced landslide or debris flow.
基金Projects supported by the Natural Science Foundation of China (No.40472134)Survey and evaluation on environmental geology of coastal zone in Liaoning,Institute of Geology and Mineral Resources (No.1212010540502)
文摘In order to understand and master the dynamic characteristics of sandy soil with different silt contents, the authors carried out many indoor dynamic triaxial tests for five groups of sandy with silt which took from Panjin and Xiamen. Under the conditions of consolidation pressure of 100 kPa, 200 kPa, 300 kPa, stationary vibration frequency H=1 and cyclic loading, the authors found that the effective cohesion increases and the effective internal friction angle decreases with the increase of the silt contents. During the liquefied scope, the cementation and the strength have been increased with the increase of the silt contents.
文摘Tropical peat swamp forest beds that have been reclaimed for agricultural use are generally an active source of nitrous oxide （N2O） efflux, however, the mechanism by which reclaimed tropical peat soils promote the emergence of N2O emitters in soil microbial communities remains unclear. The purpose of this study was to reveal the vertical distribution of N2O emission potential and its correlation with mineral nitrogen contents in reclaimed soils. Using a culture-based N2O emission assay, the N2O emission potentials of soil at various depths （0-450 cm） were investigated in two oil palm plantations in Sarawak, Malaysia, which had elapsed times of two years （E2Y） and 10 years （El 0Y） after deforestation, respectively. On the basis of the relationship between the vertical profiles of N2O emission potentials and the contents of mineralized nitrogen in the peat soils at various depths, the impact of land management on soil microbial communities was discussed. The peat soil at plantation site E2Y showed a trend of high N2O production in deep layers （200-400 cm）, whereas the older plantation site E10Y showed considerably more active N2O emission in shallow soil （10-50 cm）. N2O emission potentials among the soil microbial communities at different soil depths at the E10Y site showed positive correlations with NO3- and NH4＋ contents, whereas, soils obtained from the E2Y site had N2O emission potentials that were inversely proportional to the contents of NO3-. This contrasting vertical correlation between N2O-emitting potentials and mineralized nitrogen contents in bulk soils suggests that active N2O emission in deep soil at the E2Y site has maintained the original carbon-nitrogen （C/N） ratio of the peat soil, whereas at EIOY, such a regulatory system has been lost due to advanced soil degradation, leading to dynamic changes in the nitrogen cycle in shallow soil.
