The thermal conductivity of marine sediments is an important thermophysical parameter in the study of seafloor heat flow and marine engineering construction.Understanding the effect of thermal conductivity of marine s...The thermal conductivity of marine sediments is an important thermophysical parameter in the study of seafloor heat flow and marine engineering construction.Understanding the effect of thermal conductivity of marine sediments in the environment has a major engineering value and theoretical significance.In this work,a modified test method was used to measure the thermal conductivity of silt in the Yellow River Delta under different void ratios,moisture contents,temperatures,and salinities.Results showed that the thermal conductivity of silt in the Yellow River Delta decreased with the increase in the void ratio and increased with the water content.Compared with sand and clay,silt in the Yellow River Delta was the least affected by the void ratio and moisture content.Under low temperatures,the heat transfer of soil was controlled by the average velocity of the phonons;therefore,the thermal conductivity of silt in the Yellow River Estuary increased with temperature.The thermal conductivity of pore water decreased with increasing salinity.Moreover,certain salinity levels resulted in a phenomenon known as the‘compressing twin electrical layer’,which led to an increase in the contact area between soil particles.With the increase in salinity,the thermal conductivity of silt in the Yellow River Delta experiences an initial decline and a subsequent increase.The proposed thermal conductivity test method is more accurate than the existing technique,and the findings provide a basis for further study on the thermal characteristics of submarine sediments.展开更多
Currently,the application of the Yellow River silt in subgrade,especially in expressway subgrade,has not been widely promoted.The main reason is that the research on the mechanical characteristics of the Yellow River ...Currently,the application of the Yellow River silt in subgrade,especially in expressway subgrade,has not been widely promoted.The main reason is that the research on the mechanical characteristics of the Yellow River silt used for subgrade filling is extremely limited.In this study,the static shear test of the Yellow River silt under drained condition was carried out using Global Digital Systems(GDS)triaxial apparatus,and the effects of confining pressure,relative density and shear rate on the strength and deformation behavior of the Yellow River silt were investigated.The cohesive force of the Yellow River silt is low,and the friction angle is the main factor determining the shear strength.Friction angle at phase transformation stateφpt,friction angle at peak stateφps,friction angle at critical stateφcs,were obtained via the observation on the evolution law of mobilized friction angle during the whole shearing process.The friction angles corresponding to three different characteristic states have the following magnitude relationship,namelyφps>φcs>φpt.The strength parameters for low-grade subgrade and highgrade subgrade were chosen to be 29.33°and 33.75°.The critical state line(CSL),envelop of phase transformation(EOP),and envelop of dilatancy(EOD)for three different characteristic states were determined.The critical stress ratio M,the phase transformation stress ratio Mptand the dilatancy stress ratio Mdof the Yellow River silt are 1.199,1.235,1.152,respectively.These results provide a basis for the mechanical analysis of the Yellow River silt subgrades and the subsequent establishment of dynamic constitutive model of the Yellow River silt.展开更多
The possibility of preparing cementitious materials by the alkali-activated method using Yellow River sediment(The second largest river in China)as raw material and the modification effect on different slag addition w...The possibility of preparing cementitious materials by the alkali-activated method using Yellow River sediment(The second largest river in China)as raw material and the modification effect on different slag addition were investigated.Sodium silicate and calcium hydroxide were used as the activator,and the specimens were prepared by the press molding method.The hydration process,hydration products,pore characteristics,and mechanical properties were investigated using SEM/EDS,FTIR,TG/DTG,XRD,MIP,and uniaxial compressive strength experiments,respectively.The results showed that the compressive strength of the modified yellow river silt-based cementitious material was significantly increased when the water glass dosage was 12 wt%(Ms=1.8)and the slag dosage was 40%,and its 90-day maximum compressive strength could reach 53 MPa.展开更多
Partial drainage often occurs during piezocone penetration testing on Yellow River Delta silt because of its intermediate physical and mechanical properties between those of sand and clay.Yet,there is no accurate unde...Partial drainage often occurs during piezocone penetration testing on Yellow River Delta silt because of its intermediate physical and mechanical properties between those of sand and clay.Yet,there is no accurate understanding for the range of penetra-tion rates to trigger the partial drainage of silt soils.In order to fully investigate cone penetration rate effects under partial drainage condi-tions,indoor 1 g penetration model tests and numerical simulations of cavity expansion at variable penetration rates were carried out on the Yellow River Delta silt.The boundary effect of the model tests and the variation of key parameters at the different cavity ex-pansion rates were analyzed.The 1 g penetration model test results and numerical simulations results consistently indicated that the penetration rate to trigger the partially drainage of typical silt varied at least three orders of magnitude.The numerical simulations also provide the reference values for the penetration resistance corresponding to zero dilation and zero viscosity at any given normalized penetration rate for silt in Yellow River Delta.These geotechnical properties can be used for the design of offshore platforms in Yel-low River Delta,and the understanding of cone penetration rate effects under the partially drained conditions would provide some technical support for geohazard evaluation of offshore platforms.展开更多
The in situ pore pressure response of silt under wave action is a complex process.However,this process has not been well studied because of limited field observation techniques.The dynamic response process is closely ...The in situ pore pressure response of silt under wave action is a complex process.However,this process has not been well studied because of limited field observation techniques.The dynamic response process is closely related to engineering geological hazards;thus,this process must be urgently explored.A long-term in situ observational study of the silt sediment pore water pressure response process under wave action was conducted in the subaqueous Yellow River Delta.The response characteristics of pore water pressure are affected by tidal level and wave height.Tidal level affects the overall trend of the pore water pressure response,while wave height influences the amplitude of the pore water pressure response.This study revealed a significant lag effect in the pore pressure response.The transient pore pressure in the seabed did not respond immediately to the wave-induced pressure stress on the seabed surface.This phenomenon may be attributed to the change in soil permeability.The maximum response depth was approximately 0.5 m with a 2 m wave height.A concept model of silt soil pore pressure response under different types of wave action was developed.The accumulation rate of the pore pressure is less than the dissipation rate;thus,the developed model highlights the oscillation pore pres-sure response mechanism.The highlighted response process is of considerable importance to transient liquefaction and the startup process of pore pressure response.展开更多
The well-documented decrease in the discharge of sediment into the Yellow River has attracted considerable attention in recent years. The present study analyzed the spatial and temporal variation of sediment yield bas...The well-documented decrease in the discharge of sediment into the Yellow River has attracted considerable attention in recent years. The present study analyzed the spatial and temporal variation of sediment yield based on data from 46 hydrological stations in the sediment-rich region of the Yellow River from 1955 to 2010. The results showed that since 1970 sediment yield in the region has clearly decreased at different rates in the 45 sub-areas controlled by hydrological stations. The decrease in sediment yield was closely related to the intensity and extent of soil erosion control measures and rainstorms that occurred in different periods and sub-areas. The average sediment delivery modulus（SDM） in the study area decreased from 7,767.4 t/（km^2·a） in 1951–1969 to 980.5 t/（km^2·a） in 2000–2010. Our study suggested that 65.5% of the study area with the SDM below 1,000 t/（km^2·a） is still necessary to control soil deterioration caused by erosion, and soil erosion control measures should be further strengthened in the areas with the SDM above 1,000 t/（km^2·a）.展开更多
The upper reach of the Yellow River from Daliushu to Shapotou consists of five bends and has complex topography. A two-dimensional Re-Normalisation Group （RNG） k-ε model was developed to simulate the flow in the re...The upper reach of the Yellow River from Daliushu to Shapotou consists of five bends and has complex topography. A two-dimensional Re-Normalisation Group （RNG） k-ε model was developed to simulate the flow in the reach. In order to take the circulation currents in the bends into account, the momentum equations were improved by adding an additional source term. Comparison of the numerical simulation with field measurements indicates that the improved two-dimensional depth-averaged RNG k-e model can improve the accuracy of the numerical simulation. A rapid adaptive algorithm was constructed, which can automatically adjust Manning＇s roughness coefficient in different parts of the study river reach. As a result, not only can the trial computation time be significantly shortened, but the accuracy of the numerical simulation can also be greatly improved. Comparison of the simulated and measured water surface slopes for four typical cases shows that the longitudinal and transverse slopes of the water surface increase with the average velocity upstream. In addition, comparison was made between the positions of the talweg and the main streamline, which coincide for most of the study river reach. However, deviations between the positions of the talweg and the main streamline were found at the junction of two bends, at the position where the river width suddenly decreases or increases.展开更多
In order to consume the Yellow River sediment as much as possible and improve the longterm stability of the Yellow River, Yellow River sediment was utilized as the main raw material to produce a composite material. Ca...In order to consume the Yellow River sediment as much as possible and improve the longterm stability of the Yellow River, Yellow River sediment was utilized as the main raw material to produce a composite material. Ca(OH)_2 was used as alkali-activator to activate the active SiO_2 and Al_2O_3 compositions in Yellow River sediment. 10 wt% slag was added into the mixture to further improve the strength of the composites. The effect of activity rate of the Yellow River sediment and dosage of Ca(OH) _2 on the compressive strength of the Yellow River sediment-slag composite material at different curing ages was researched. XRD, SEM/EDS, light microscope and FTIR were used to further explore the products and the microstructure of the composite material. Results showed that the active ratio of sediment had a great influence on the compressive strength of specimen. In addition, the compressive strength of specimen increased with the increase of Ca(OH)_2dosage and curing age. When the dosage of Ca(OH)_2 was more than 5 wt% as well as the curing age reached 90 days, the compressive strength of the composite material could meet the engineering requirement. In the alkali-activated process, the main product was hydrated calcium silicate(C-S-H) gel, which filled up the gaps among the sediment particles and decreased the porosity of the specimen. Moreover, the CaCO_3 produced by the carbonization of the C-S-H gel and excess Ca(OH)_2 also played a role on the strength.展开更多
The Yellow River has a vast catchment area and historically it is the mother river of the Chinese nation. Now it serves as one of the main theatres for the on-going national campaign to develop China's western... The Yellow River has a vast catchment area and historically it is the mother river of the Chinese nation. Now it serves as one of the main theatres for the on-going national campaign to develop China's western hinterland.……展开更多
基金The authors would like to thank the National Natural Science Foundation of China(Nos.U2006213,42277139,42207172)the China Postdoctoral Science Foundation(No.2022M712989)the Natural Science Foundation of Shandong Province(No.ZR2022QD103).
文摘The thermal conductivity of marine sediments is an important thermophysical parameter in the study of seafloor heat flow and marine engineering construction.Understanding the effect of thermal conductivity of marine sediments in the environment has a major engineering value and theoretical significance.In this work,a modified test method was used to measure the thermal conductivity of silt in the Yellow River Delta under different void ratios,moisture contents,temperatures,and salinities.Results showed that the thermal conductivity of silt in the Yellow River Delta decreased with the increase in the void ratio and increased with the water content.Compared with sand and clay,silt in the Yellow River Delta was the least affected by the void ratio and moisture content.Under low temperatures,the heat transfer of soil was controlled by the average velocity of the phonons;therefore,the thermal conductivity of silt in the Yellow River Estuary increased with temperature.The thermal conductivity of pore water decreased with increasing salinity.Moreover,certain salinity levels resulted in a phenomenon known as the‘compressing twin electrical layer’,which led to an increase in the contact area between soil particles.With the increase in salinity,the thermal conductivity of silt in the Yellow River Delta experiences an initial decline and a subsequent increase.The proposed thermal conductivity test method is more accurate than the existing technique,and the findings provide a basis for further study on the thermal characteristics of submarine sediments.
基金National Natural Science Foundation of China(Grant Nos.5217836952109140)+4 种基金Key Projects of High Schools of Henan province of China(20A560021)Natural Science Foundation of Henan Province of China(202300410424)Youth Talent Promotion Project of Henan Province of China(2021HYTP016)Key Specialized Research and Development Breakthrough in Henan Province of China(212102310977)China Postdoctoral Science Foundation(2019M662533)。
文摘Currently,the application of the Yellow River silt in subgrade,especially in expressway subgrade,has not been widely promoted.The main reason is that the research on the mechanical characteristics of the Yellow River silt used for subgrade filling is extremely limited.In this study,the static shear test of the Yellow River silt under drained condition was carried out using Global Digital Systems(GDS)triaxial apparatus,and the effects of confining pressure,relative density and shear rate on the strength and deformation behavior of the Yellow River silt were investigated.The cohesive force of the Yellow River silt is low,and the friction angle is the main factor determining the shear strength.Friction angle at phase transformation stateφpt,friction angle at peak stateφps,friction angle at critical stateφcs,were obtained via the observation on the evolution law of mobilized friction angle during the whole shearing process.The friction angles corresponding to three different characteristic states have the following magnitude relationship,namelyφps>φcs>φpt.The strength parameters for low-grade subgrade and highgrade subgrade were chosen to be 29.33°and 33.75°.The critical state line(CSL),envelop of phase transformation(EOP),and envelop of dilatancy(EOD)for three different characteristic states were determined.The critical stress ratio M,the phase transformation stress ratio Mptand the dilatancy stress ratio Mdof the Yellow River silt are 1.199,1.235,1.152,respectively.These results provide a basis for the mechanical analysis of the Yellow River silt subgrades and the subsequent establishment of dynamic constitutive model of the Yellow River silt.
基金Funded in part by the Joint Funds of National Natural Science Foundation of China(No.U20A20324)National Natural Science Foundation of China(No.51878116)+3 种基金Liaoning Province Key Project of Research and Development Plan(No.2020JH2/10100016)Dalian Science and Technology Innovation Fund Project(No.2020JJ26SN060)the National Natural Science Foundation of China(No.51809109)the National Key Research and Development Projects(No.2017YFC0504506)。
文摘The possibility of preparing cementitious materials by the alkali-activated method using Yellow River sediment(The second largest river in China)as raw material and the modification effect on different slag addition were investigated.Sodium silicate and calcium hydroxide were used as the activator,and the specimens were prepared by the press molding method.The hydration process,hydration products,pore characteristics,and mechanical properties were investigated using SEM/EDS,FTIR,TG/DTG,XRD,MIP,and uniaxial compressive strength experiments,respectively.The results showed that the compressive strength of the modified yellow river silt-based cementitious material was significantly increased when the water glass dosage was 12 wt%(Ms=1.8)and the slag dosage was 40%,and its 90-day maximum compressive strength could reach 53 MPa.
基金supported by the National Natural Science Foundation of China(Nos.U1806230,U2006213),and the Fundamental Research Funds for the Central Univer-sities(No.201962011).
文摘Partial drainage often occurs during piezocone penetration testing on Yellow River Delta silt because of its intermediate physical and mechanical properties between those of sand and clay.Yet,there is no accurate understanding for the range of penetra-tion rates to trigger the partial drainage of silt soils.In order to fully investigate cone penetration rate effects under partial drainage condi-tions,indoor 1 g penetration model tests and numerical simulations of cavity expansion at variable penetration rates were carried out on the Yellow River Delta silt.The boundary effect of the model tests and the variation of key parameters at the different cavity ex-pansion rates were analyzed.The 1 g penetration model test results and numerical simulations results consistently indicated that the penetration rate to trigger the partially drainage of typical silt varied at least three orders of magnitude.The numerical simulations also provide the reference values for the penetration resistance corresponding to zero dilation and zero viscosity at any given normalized penetration rate for silt in Yellow River Delta.These geotechnical properties can be used for the design of offshore platforms in Yel-low River Delta,and the understanding of cone penetration rate effects under the partially drained conditions would provide some technical support for geohazard evaluation of offshore platforms.
基金sponsored by the National Special Project for Marine Public Welfare Industry(No.201005005)the National Natural Science Foundation of China(Nos.42107207,41876066)+1 种基金the Natural Science Foundation of Shandong Province(No.ZR2020QD067)the Post-doctoral Innovation Project of Shandong Province(No.202002042)。
文摘The in situ pore pressure response of silt under wave action is a complex process.However,this process has not been well studied because of limited field observation techniques.The dynamic response process is closely related to engineering geological hazards;thus,this process must be urgently explored.A long-term in situ observational study of the silt sediment pore water pressure response process under wave action was conducted in the subaqueous Yellow River Delta.The response characteristics of pore water pressure are affected by tidal level and wave height.Tidal level affects the overall trend of the pore water pressure response,while wave height influences the amplitude of the pore water pressure response.This study revealed a significant lag effect in the pore pressure response.The transient pore pressure in the seabed did not respond immediately to the wave-induced pressure stress on the seabed surface.This phenomenon may be attributed to the change in soil permeability.The maximum response depth was approximately 0.5 m with a 2 m wave height.A concept model of silt soil pore pressure response under different types of wave action was developed.The accumulation rate of the pore pressure is less than the dissipation rate;thus,the developed model highlights the oscillation pore pres-sure response mechanism.The highlighted response process is of considerable importance to transient liquefaction and the startup process of pore pressure response.
基金funded by the Major Programs of the Chinese Academy of Sciences (KZZD-EW-04-03-04)the National Science-technology Support Plan Project (2006BAD09B10)the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-EW-406)
文摘The well-documented decrease in the discharge of sediment into the Yellow River has attracted considerable attention in recent years. The present study analyzed the spatial and temporal variation of sediment yield based on data from 46 hydrological stations in the sediment-rich region of the Yellow River from 1955 to 2010. The results showed that since 1970 sediment yield in the region has clearly decreased at different rates in the 45 sub-areas controlled by hydrological stations. The decrease in sediment yield was closely related to the intensity and extent of soil erosion control measures and rainstorms that occurred in different periods and sub-areas. The average sediment delivery modulus（SDM） in the study area decreased from 7,767.4 t/（km^2·a） in 1951–1969 to 980.5 t/（km^2·a） in 2000–2010. Our study suggested that 65.5% of the study area with the SDM below 1,000 t/（km^2·a） is still necessary to control soil deterioration caused by erosion, and soil erosion control measures should be further strengthened in the areas with the SDM above 1,000 t/（km^2·a）.
基金supported by the National Natural Science Foundation of China(Grants No.11361002 and 91230111)the Natural Science Foundation of Ningxia,China(Grant No.NZ13086)+1 种基金the Project of Beifang University of Nationalities,China(Grant No.2012XZK05)the Foreign Expert Project of Beifang University of Nationalities,China,and the Visiting Scholar Foundation of State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University,China(Grant No.2013A011)
文摘The upper reach of the Yellow River from Daliushu to Shapotou consists of five bends and has complex topography. A two-dimensional Re-Normalisation Group （RNG） k-ε model was developed to simulate the flow in the reach. In order to take the circulation currents in the bends into account, the momentum equations were improved by adding an additional source term. Comparison of the numerical simulation with field measurements indicates that the improved two-dimensional depth-averaged RNG k-e model can improve the accuracy of the numerical simulation. A rapid adaptive algorithm was constructed, which can automatically adjust Manning＇s roughness coefficient in different parts of the study river reach. As a result, not only can the trial computation time be significantly shortened, but the accuracy of the numerical simulation can also be greatly improved. Comparison of the simulated and measured water surface slopes for four typical cases shows that the longitudinal and transverse slopes of the water surface increase with the average velocity upstream. In addition, comparison was made between the positions of the talweg and the main streamline, which coincide for most of the study river reach. However, deviations between the positions of the talweg and the main streamline were found at the junction of two bends, at the position where the river width suddenly decreases or increases.
基金Funded by the National Natural Science Foundation of China(Nos.51578108,51878116,51809109)the Fundamental Research Fund for the Central Universities(No.DUT18ZD219)National Key R&D Program of China(No.2017YFC0504506)
文摘In order to consume the Yellow River sediment as much as possible and improve the longterm stability of the Yellow River, Yellow River sediment was utilized as the main raw material to produce a composite material. Ca(OH)_2 was used as alkali-activator to activate the active SiO_2 and Al_2O_3 compositions in Yellow River sediment. 10 wt% slag was added into the mixture to further improve the strength of the composites. The effect of activity rate of the Yellow River sediment and dosage of Ca(OH) _2 on the compressive strength of the Yellow River sediment-slag composite material at different curing ages was researched. XRD, SEM/EDS, light microscope and FTIR were used to further explore the products and the microstructure of the composite material. Results showed that the active ratio of sediment had a great influence on the compressive strength of specimen. In addition, the compressive strength of specimen increased with the increase of Ca(OH)_2dosage and curing age. When the dosage of Ca(OH)_2 was more than 5 wt% as well as the curing age reached 90 days, the compressive strength of the composite material could meet the engineering requirement. In the alkali-activated process, the main product was hydrated calcium silicate(C-S-H) gel, which filled up the gaps among the sediment particles and decreased the porosity of the specimen. Moreover, the CaCO_3 produced by the carbonization of the C-S-H gel and excess Ca(OH)_2 also played a role on the strength.
文摘 The Yellow River has a vast catchment area and historically it is the mother river of the Chinese nation. Now it serves as one of the main theatres for the on-going national campaign to develop China's western hinterland.……
