Correlation and path analysis methods were used to study the relationship between soil properties and the distribution of different soil Hg fractions with nine representative soils from Chongqing, China. Results showe...Correlation and path analysis methods were used to study the relationship between soil properties and the distribution of different soil Hg fractions with nine representative soils from Chongqing, China. Results showed that clay (< 2 m) could increase water-soluble Hg (r = 0.700*). Soil organic matter (OM) could enhance the increase of elemental Hg (r = 0.674*). The higher the base saturation percentage (BSP), the more the residual Hg (T = 0.684*). Organic Hg, the sum of acid-soluble organic Hg and alkali-soluble Hg, was positively affected by silt (2-20 μm) but negatively affected by pH, with the direct path coefficients amounting to 1.0487 and 0.5121, respectively. The positive effect of OM and negative effect of BSP on organic Hg were the most significant, with the direct path coefficients being 0.7614 and -0.8527, respectively. The indirect effect of clay (< 2 μm) via BSP (path coefficient = 0.4186) was the highest, showing that the real influencing factor in the effect of clay (< 2 μm) on acid-soluble organic Hg was BSP. Since the available Hg fraction, water-soluble Hg, was positively affected by soil clay content, and the quite immobile and not bioavailable residual Hg by soil BSP, suitable reduction of clay content and increase of BSP would be of much help to reduce the Hg availability and Hg activity in Hg-contaminated soils.展开更多
The influence on fine particle aggregation and flotation behavior induced by high intensity conditioning(HIC) from saturated of the slurry with CO2 saturation was investigated.Bubble size measurements were conducted.T...The influence on fine particle aggregation and flotation behavior induced by high intensity conditioning(HIC) from saturated of the slurry with CO2 saturation was investigated.Bubble size measurements were conducted.The effect of dissolved gas,xanthate addition and agitation speed on fine sphalerite particle aggregation-and flotation-behavior were studied.The results show that during HIC in air or CO2 saturated water xanthate acts as a frother.The dissolved gas content in the pulp and HIC play a synergistic role in promoting fine particle aggregation and hence flotation;a significantly enhanced aggregation of fine sphalerite particles in a CO2 saturated slurry by HIC is observed.The aggregate size increased when the agitation speed was increased from 700 r/min to 1500 r/min.Increasing the HIC speed to 1500 r/min caused a positive impact on flotation kinetics.Further increasing the speed to 2000 r/min resulted in an adverse effect on flotation kinetics.展开更多
Gibbsite is the usual precipitation product from alumina refineries with either Bayer or sintering process.However,the advantage of boehmite precipitation over gibbsite precipitation is the significant energy saving i...Gibbsite is the usual precipitation product from alumina refineries with either Bayer or sintering process.However,the advantage of boehmite precipitation over gibbsite precipitation is the significant energy saving in the subsequent calcination step.The current investigation takes a pragmatic approach to measure precipitation ratios,determine product phase,morphology and particle size distribution,and assess the impacts and adjustment capability of main parameters such as seed,temperature,ethanol medium,and supersaturation on the precipitation kinetics and alumina hydrate type during co-precipitation process.The results clarify that gibbsite and boehmite both can be precipitated from supersaturated sodium aluminate solutions simultaneously,and the competitive formation between Al(OH)3 and γ-AlOOH determines the main precipitate phases from pregnant liquor.Boehmite seeds,high temperature and ethanol addition can promote the boehmite precipitation and improve the mass fraction of boehmite in products.Co-precipitation changes the multimodal distribution of seeds to a normal and well distribution of products,and the particle size is more than several times that of seeds.展开更多
The use of marginal backfills in GSE （geosynthetic stabilized earth） walls has not been recommended by different standards specifications. Restrictions are motivated by the poor hydraulic conductivity of fine soils ...The use of marginal backfills in GSE （geosynthetic stabilized earth） walls has not been recommended by different standards specifications. Restrictions are motivated by the poor hydraulic conductivity of fine soils that are capable of developing of water pressures. However, the use of granular materials can expend the cost of the construction. As a result, local soils, granular or not, have been increasingly used. Unsaturated conditions of fine soils may result in convenient performance even using extensible reinforcements. This paper evaluates the performance of a full scale model of a nonwoven geotextile reinforced wall constructed with fine grained soil backfill. The unsaturated condition was maintained and matric suctions, displacements and reinforcement strains were monitored during the test. Results have shown that the unsaturated condition of the backfill allowed maximum reinforcement peak strain of 0.4 %. For the case of a wrap faced wall on a firm foundation the performance and good agreement between measured strains and factors of safety from limit equilibrium analyses have shown the maintenance of unsaturated conditions as an economical alternative to the use of high quality fill.展开更多
An effective thermal conductivity model was proposed for unsaturated compacted bentonites with consideration of the bimodal shape of pore size distribution curves. The pores of soils were grouped into two dominant por...An effective thermal conductivity model was proposed for unsaturated compacted bentonites with consideration of the bimodal shape of pore size distribution curves. The pores of soils were grouped into two dominant pore size modes corresponding to the intra- and inter-particle pores, and were simulated with randomly distributed spheroidal inclusions of different aspect ratios. With the assumption of preferential invasion of the wetting fluid （water） into pores of smaller sizes and by virtue of the analyt- ical solution to the inhomogeneous inclusion problem in heat conduction, the model was developed using the Mori-Tanaka （MT）, Ponte Castafieda-Willis （PCW） and self-consistent （SC） homogenization approaches for different considerations of the interactions between pores and the solid phase. The proposed model is functions of the thermal conductivities of the solid, liq- uid and gas phases, porosity, the degree of saturation, the aspect ratios of pores and/or soil particles, and the fraction of the smaller group of pores. The proposed model was validated against five sets of laboratory measurement data on the MX-80, FEBEX, KunigeI-V1 and GMZ01 bentonites, showing a good agreement between the model predictions and the laboratory measurements. The responses of the model with respect to the geometries of pores and solid particles were examined. Com- pared to series-parallel structural models, the proposed model may overall exhibit better performance if proper homogenization schemes are adopted, but as an advantage, the model has clearer physical mechanisms and a smaller number of parameters.展开更多
基金the Doctoral Foundation, Education Ministry of China (No. 970601) and the BeijingNatural Science Foundation, China (No. 699000
文摘Correlation and path analysis methods were used to study the relationship between soil properties and the distribution of different soil Hg fractions with nine representative soils from Chongqing, China. Results showed that clay (< 2 m) could increase water-soluble Hg (r = 0.700*). Soil organic matter (OM) could enhance the increase of elemental Hg (r = 0.674*). The higher the base saturation percentage (BSP), the more the residual Hg (T = 0.684*). Organic Hg, the sum of acid-soluble organic Hg and alkali-soluble Hg, was positively affected by silt (2-20 μm) but negatively affected by pH, with the direct path coefficients amounting to 1.0487 and 0.5121, respectively. The positive effect of OM and negative effect of BSP on organic Hg were the most significant, with the direct path coefficients being 0.7614 and -0.8527, respectively. The indirect effect of clay (< 2 μm) via BSP (path coefficient = 0.4186) was the highest, showing that the real influencing factor in the effect of clay (< 2 μm) on acid-soluble organic Hg was BSP. Since the available Hg fraction, water-soluble Hg, was positively affected by soil clay content, and the quite immobile and not bioavailable residual Hg by soil BSP, suitable reduction of clay content and increase of BSP would be of much help to reduce the Hg availability and Hg activity in Hg-contaminated soils.
基金Project 50674103 supported by the National Natural Science Foundation of China
文摘The influence on fine particle aggregation and flotation behavior induced by high intensity conditioning(HIC) from saturated of the slurry with CO2 saturation was investigated.Bubble size measurements were conducted.The effect of dissolved gas,xanthate addition and agitation speed on fine sphalerite particle aggregation-and flotation-behavior were studied.The results show that during HIC in air or CO2 saturated water xanthate acts as a frother.The dissolved gas content in the pulp and HIC play a synergistic role in promoting fine particle aggregation and hence flotation;a significantly enhanced aggregation of fine sphalerite particles in a CO2 saturated slurry by HIC is observed.The aggregate size increased when the agitation speed was increased from 700 r/min to 1500 r/min.Increasing the HIC speed to 1500 r/min caused a positive impact on flotation kinetics.Further increasing the speed to 2000 r/min resulted in an adverse effect on flotation kinetics.
基金Projects(50704030) supported by the National Natural Science Foundation of ChinaProject(KGCX2-YW-321-2) supported by the Knowledge Innovation Program of the Chinese Academy of Sciences
文摘Gibbsite is the usual precipitation product from alumina refineries with either Bayer or sintering process.However,the advantage of boehmite precipitation over gibbsite precipitation is the significant energy saving in the subsequent calcination step.The current investigation takes a pragmatic approach to measure precipitation ratios,determine product phase,morphology and particle size distribution,and assess the impacts and adjustment capability of main parameters such as seed,temperature,ethanol medium,and supersaturation on the precipitation kinetics and alumina hydrate type during co-precipitation process.The results clarify that gibbsite and boehmite both can be precipitated from supersaturated sodium aluminate solutions simultaneously,and the competitive formation between Al(OH)3 and γ-AlOOH determines the main precipitate phases from pregnant liquor.Boehmite seeds,high temperature and ethanol addition can promote the boehmite precipitation and improve the mass fraction of boehmite in products.Co-precipitation changes the multimodal distribution of seeds to a normal and well distribution of products,and the particle size is more than several times that of seeds.
文摘The use of marginal backfills in GSE （geosynthetic stabilized earth） walls has not been recommended by different standards specifications. Restrictions are motivated by the poor hydraulic conductivity of fine soils that are capable of developing of water pressures. However, the use of granular materials can expend the cost of the construction. As a result, local soils, granular or not, have been increasingly used. Unsaturated conditions of fine soils may result in convenient performance even using extensible reinforcements. This paper evaluates the performance of a full scale model of a nonwoven geotextile reinforced wall constructed with fine grained soil backfill. The unsaturated condition was maintained and matric suctions, displacements and reinforcement strains were monitored during the test. Results have shown that the unsaturated condition of the backfill allowed maximum reinforcement peak strain of 0.4 %. For the case of a wrap faced wall on a firm foundation the performance and good agreement between measured strains and factors of safety from limit equilibrium analyses have shown the maintenance of unsaturated conditions as an economical alternative to the use of high quality fill.
基金supported by the National Natural Science Foundation of China(Grant Nos.51179136 and 51222903)
文摘An effective thermal conductivity model was proposed for unsaturated compacted bentonites with consideration of the bimodal shape of pore size distribution curves. The pores of soils were grouped into two dominant pore size modes corresponding to the intra- and inter-particle pores, and were simulated with randomly distributed spheroidal inclusions of different aspect ratios. With the assumption of preferential invasion of the wetting fluid （water） into pores of smaller sizes and by virtue of the analyt- ical solution to the inhomogeneous inclusion problem in heat conduction, the model was developed using the Mori-Tanaka （MT）, Ponte Castafieda-Willis （PCW） and self-consistent （SC） homogenization approaches for different considerations of the interactions between pores and the solid phase. The proposed model is functions of the thermal conductivities of the solid, liq- uid and gas phases, porosity, the degree of saturation, the aspect ratios of pores and/or soil particles, and the fraction of the smaller group of pores. The proposed model was validated against five sets of laboratory measurement data on the MX-80, FEBEX, KunigeI-V1 and GMZ01 bentonites, showing a good agreement between the model predictions and the laboratory measurements. The responses of the model with respect to the geometries of pores and solid particles were examined. Com- pared to series-parallel structural models, the proposed model may overall exhibit better performance if proper homogenization schemes are adopted, but as an advantage, the model has clearer physical mechanisms and a smaller number of parameters.
