With the aid of soil column test models,the transport rules of fluorine contaminants in unsaturated stratified soils are discussed. Curves of F-concentrations at different times and sites in the unsaturated stratified...With the aid of soil column test models,the transport rules of fluorine contaminants in unsaturated stratified soils are discussed. Curves of F-concentrations at different times and sites in the unsaturated stratified soil were ob-tained under conditions of continuous injection of fluoride contaminants and water. Based on the analysis of the actual observation data,the values between computed results and observed data were compared. It is shown that the chemical properties of fluorine ions are active. The migration process of fluorine ions in soils is complex. Because of the effect of adsorption and desorption,the curve of the fluorine ion breakthrough curve is not symmetric. Its concentration peak value at each measuring point gradually decays. The tail of the breakthrough curve is long and the process of leaching and purifying using water requires considerable time. Along with the release of OHˉ in the process of fluorine absorp-tion,the pH value of the soil solution changed from neutral to alkalinity during the test process. The first part of the breakthrough curve fitted better than the second part. The main reason is that fluorine does not always exist in the form of fluorinions in groundwater. Given the long test time,fluorinions possibly react with other ions in the soil solution to form complex water-soluble fluorine compounds. Only the retardation factor and source-sink term have been considered in our numerical model,which may leads to errors of computed values. But as a whole the migration rules of fluorine ions are basically correct,which indicates that the established numerical model can be used to simulate the transport rules of fluorine contaminants in unsaturated stratified soils.展开更多
To develop a sound post-treatment process for anaerobically-digested strong wastewater,a novel natural treatment system comprising two units is put forward.The first unit,a trickling filter,provides for further reduct...To develop a sound post-treatment process for anaerobically-digested strong wastewater,a novel natural treatment system comprising two units is put forward.The first unit,a trickling filter,provides for further reduction of biochemical oxygen demand and adjustable nitrification.The subsequent soil–plant unit aims at removing and recovering the nutrients nitrogen（N）,phosphorus（P）and potassium（K）.As a lab-scale feasibility study,a soil column test was conducted,in which black soil and valuable Kentucky bluegrass were integrated to treat artificial nutrient-enriched wastewater.After a long-term operation,the nitrification function was well established in the top layers,despite the need for an improved denitrification process prior to discharge.P and K were retained by the soil through distinct mechanisms.Since they either partially or totally remained in plant-available forms in the soil,indirect nutrient reuse could be achieved.As for Kentucky bluegrass,it displayed better growth status when receiving wastewater,with direct recovery of 8%,6% and 14% of input N,P and K,respectively.Furthermore,the indispensable role of Kentucky bluegrass for better treatment performance was proved,as it enhanced the cell-specific nitrification potential of the soil nitrifying microorganisms inhabiting the rhizosphere.After further upgrade,the proposed system is expected to become a new solution for strong wastewater pollution.展开更多
The dynamic shear modulus for three types of undisturbed soil under different consolidation ratios is presented by using the resonant column test method. Its effects on surface ground motion is illustrated by calculat...The dynamic shear modulus for three types of undisturbed soil under different consolidation ratios is presented by using the resonant column test method. Its effects on surface ground motion is illustrated by calculation. The test results indicate that the power function is a suitable form for describing the relationship between the ratio of the maximum dynamic shear modulus due to anisotropic and isotropic consolidations and the increment of the consolidation ratio. When compared to sand, the increment of the maximum dynamic shear modulus for undisturbed soil due to anisotropic consolidation is much larger. Using a one-dimensional equivalent linearization method, the earthquake influence factor and the characteristic period of the surface acceleration are calculated for two soil layers subjected to several typical earthquake waves. The calculated results show that the difference in nonlinear properties due to different consolidation ratios is generally not very notable, but the degree of its influence on the surface acceleration spectrum is remarkable for the occurrence of strong earthquakes. When compared to isotropic consolidation, the consideration of actual anisotropic consolidation causes the characteristic period to decrease and the earthquake influence factor to increase.展开更多
Liquefaction is one of the most destructive natural hazards that cause damage to engineering structures during an earthquake. This study aims to examine the effect of rubber and gravel drainage columns on the reductio...Liquefaction is one of the most destructive natural hazards that cause damage to engineering structures during an earthquake. This study aims to examine the effect of rubber and gravel drainage columns on the reduction of liquefaction potential of saturated sandy soils using a shaking table. Experiments were carried out in various conditions such as construction materials, different arrangements and diameters of drainage columns. Effects of the relative density and the input motion on the base test were investigated as well. The results demonstrate that rubber drainage columns have slightly better performance compared to gravel drainage columns at high relative density and high input acceleration. Soil improvement using gravel drainage columns, which leads to reduction in liquefaction effects at moderate input acceleration and low relative density, is a more effective method than that using rubber drainage columns. By increasing the number and diameter of gravel and rubber drainage columns, deformations due to liquefaction are reduced. The drainage rate of gravel drains is higher than that of rubber drains after shaking. Totally, the outcomes indicate that densification is the most important factor controlling liquefaction.展开更多
为研究水泥土复合管桩扩大桩尖技术方法的适用情况,依托福建某大面积挖填方厂区工程项目,选取两根桩型均为PHC 400 AB 600的管桩,分别采用常规桩尖和扩大桩尖技术。利用现场静荷载试验,获取两根桩的Q~s曲线,并通过不同断面安装钢筋计来...为研究水泥土复合管桩扩大桩尖技术方法的适用情况,依托福建某大面积挖填方厂区工程项目,选取两根桩型均为PHC 400 AB 600的管桩,分别采用常规桩尖和扩大桩尖技术。利用现场静荷载试验,获取两根桩的Q~s曲线,并通过不同断面安装钢筋计来获取每级断面处桩身轴力值,获得两根桩的桩身轴力分布情况。结果显示,在相同桩顶荷载下,采取扩大桩尖技术的管桩桩端沉降量大于采取常规桩尖技术的管桩桩端沉降量,且扩大桩尖技术能够有效提升桩端阻力发挥程度。在施工后通过开挖桩周土,利用管桩测斜仪,发现采用扩大桩尖技术能够有效提升桩身垂直度。展开更多
基金Project 50239010 supported by the National Natural Science Foundation of China
文摘With the aid of soil column test models,the transport rules of fluorine contaminants in unsaturated stratified soils are discussed. Curves of F-concentrations at different times and sites in the unsaturated stratified soil were ob-tained under conditions of continuous injection of fluoride contaminants and water. Based on the analysis of the actual observation data,the values between computed results and observed data were compared. It is shown that the chemical properties of fluorine ions are active. The migration process of fluorine ions in soils is complex. Because of the effect of adsorption and desorption,the curve of the fluorine ion breakthrough curve is not symmetric. Its concentration peak value at each measuring point gradually decays. The tail of the breakthrough curve is long and the process of leaching and purifying using water requires considerable time. Along with the release of OHˉ in the process of fluorine absorp-tion,the pH value of the soil solution changed from neutral to alkalinity during the test process. The first part of the breakthrough curve fitted better than the second part. The main reason is that fluorine does not always exist in the form of fluorinions in groundwater. Given the long test time,fluorinions possibly react with other ions in the soil solution to form complex water-soluble fluorine compounds. Only the retardation factor and source-sink term have been considered in our numerical model,which may leads to errors of computed values. But as a whole the migration rules of fluorine ions are basically correct,which indicates that the established numerical model can be used to simulate the transport rules of fluorine contaminants in unsaturated stratified soils.
基金greatly supported by the Japan Society for the Promotion of Science(JSPS)KAKENHI Grant Number 26303012
文摘To develop a sound post-treatment process for anaerobically-digested strong wastewater,a novel natural treatment system comprising two units is put forward.The first unit,a trickling filter,provides for further reduction of biochemical oxygen demand and adjustable nitrification.The subsequent soil–plant unit aims at removing and recovering the nutrients nitrogen（N）,phosphorus（P）and potassium（K）.As a lab-scale feasibility study,a soil column test was conducted,in which black soil and valuable Kentucky bluegrass were integrated to treat artificial nutrient-enriched wastewater.After a long-term operation,the nitrification function was well established in the top layers,despite the need for an improved denitrification process prior to discharge.P and K were retained by the soil through distinct mechanisms.Since they either partially or totally remained in plant-available forms in the soil,indirect nutrient reuse could be achieved.As for Kentucky bluegrass,it displayed better growth status when receiving wastewater,with direct recovery of 8%,6% and 14% of input N,P and K,respectively.Furthermore,the indispensable role of Kentucky bluegrass for better treatment performance was proved,as it enhanced the cell-specific nitrification potential of the soil nitrifying microorganisms inhabiting the rhizosphere.After further upgrade,the proposed system is expected to become a new solution for strong wastewater pollution.
基金National Natural Science Foundation of China under Grant No.51108163Natural Science Foundation of Heilongjiang Province under Grant No.E201104
文摘The dynamic shear modulus for three types of undisturbed soil under different consolidation ratios is presented by using the resonant column test method. Its effects on surface ground motion is illustrated by calculation. The test results indicate that the power function is a suitable form for describing the relationship between the ratio of the maximum dynamic shear modulus due to anisotropic and isotropic consolidations and the increment of the consolidation ratio. When compared to sand, the increment of the maximum dynamic shear modulus for undisturbed soil due to anisotropic consolidation is much larger. Using a one-dimensional equivalent linearization method, the earthquake influence factor and the characteristic period of the surface acceleration are calculated for two soil layers subjected to several typical earthquake waves. The calculated results show that the difference in nonlinear properties due to different consolidation ratios is generally not very notable, but the degree of its influence on the surface acceleration spectrum is remarkable for the occurrence of strong earthquakes. When compared to isotropic consolidation, the consideration of actual anisotropic consolidation causes the characteristic period to decrease and the earthquake influence factor to increase.
文摘Liquefaction is one of the most destructive natural hazards that cause damage to engineering structures during an earthquake. This study aims to examine the effect of rubber and gravel drainage columns on the reduction of liquefaction potential of saturated sandy soils using a shaking table. Experiments were carried out in various conditions such as construction materials, different arrangements and diameters of drainage columns. Effects of the relative density and the input motion on the base test were investigated as well. The results demonstrate that rubber drainage columns have slightly better performance compared to gravel drainage columns at high relative density and high input acceleration. Soil improvement using gravel drainage columns, which leads to reduction in liquefaction effects at moderate input acceleration and low relative density, is a more effective method than that using rubber drainage columns. By increasing the number and diameter of gravel and rubber drainage columns, deformations due to liquefaction are reduced. The drainage rate of gravel drains is higher than that of rubber drains after shaking. Totally, the outcomes indicate that densification is the most important factor controlling liquefaction.
文摘为研究水泥土复合管桩扩大桩尖技术方法的适用情况,依托福建某大面积挖填方厂区工程项目,选取两根桩型均为PHC 400 AB 600的管桩,分别采用常规桩尖和扩大桩尖技术。利用现场静荷载试验,获取两根桩的Q~s曲线,并通过不同断面安装钢筋计来获取每级断面处桩身轴力值,获得两根桩的桩身轴力分布情况。结果显示,在相同桩顶荷载下,采取扩大桩尖技术的管桩桩端沉降量大于采取常规桩尖技术的管桩桩端沉降量,且扩大桩尖技术能够有效提升桩端阻力发挥程度。在施工后通过开挖桩周土,利用管桩测斜仪,发现采用扩大桩尖技术能够有效提升桩身垂直度。
