In order to explore the mechanical properties and microstructure changes of frozen saline silty clay in the Hexi region of Gansu Province,triaxial compression tests and scanning electron microscopy(SEM)analysis experi...In order to explore the mechanical properties and microstructure changes of frozen saline silty clay in the Hexi region of Gansu Province,triaxial compression tests and scanning electron microscopy(SEM)analysis experiment were conducted to explore the effects of moisture content,confining pressure,and temperature on the stress-strain characteristics and failure modes of frozen soil,as well as the changes in the internal microstructure of the sample.The experimental results show that the strength of frozen sulfate saline soil first increases and then decreases with the increase of moisture content,and the maximum strength corresponds to a moisture content of 15%.The changes in confining pressure and strength have the same trend.The lower the temperature,the greater the strength of the sample.During the entire loading process,the specimens undergo a gradual transition from volume shrinkage to volume expansion.Due to the strain harden behavior of the stress-strain curve throughout the entire loading process,the failure mode of the specimens is plastic failure.The internal microstructure of the sample gradually transitions from point-point contact and edge-point contact before shearing to edge-surface contact and edge-edge contact after shearing,and the pore size inside the sample increases after shearing,with a loose arrangement of the particle skeleton.The above research conclusions can lay a certain theoretical foun-dation for the engineering design and construction of sulfate saline soil in cold and arid areas.展开更多
The capillary interactions, including the capillary force and capillary suction, between two unequal-sized particles with a fixed liquid volume are investigated. The cap- illary interaction model is used within the Yo...The capillary interactions, including the capillary force and capillary suction, between two unequal-sized particles with a fixed liquid volume are investigated. The cap- illary interaction model is used within the Young-Laplace framework. With the profile of the meridian of the liquid bridge, the capillary suction, and the liquid volume as state variables, the governing equations with two-fixed-point boundary axe first derived using a variable substitution technique, in which the gravity effects are neglected. The capillary suction and geometry of the liquid bridge with a fixed volume are solved with a shooting method. In modeling the capillary force, the Gorge method is applied. The effects of var- ious parameters including the distance between two particles, the ratio of particle radii, and the liquid-solid contact angles are discussed.展开更多
The amount of rainfall varies unevenly in different regions of the Qinghai-Tibet Plateau,with some regions becoming wetter and others drier.Precipitation has an important impact on the process of surface energy balanc...The amount of rainfall varies unevenly in different regions of the Qinghai-Tibet Plateau,with some regions becoming wetter and others drier.Precipitation has an important impact on the process of surface energy balance and the energy-water transfer within soils.To clarify the thermal-moisture dynamics and thermal stability of the active layer in permafrost regions under wet/dry conditions,the verified water-vapour-heat coupling model was used.Changes in the surface energy balance,energy-water transfer within the soil,and thickness of the active layer were quantitatively analyzed.The results demonstrate that rainfall changes significantly affect the Bowen ratio,which in turn affects surface energy exchange.Under wet/dry conditions,there is a positive correlation between rainfall and liquid water flux under the hydraulic gradient;water vapour migration is the main form under the temperature gradient,which indicates that the influence of water vapour migration on thermalmoisture dynamics of the active layer cannot be neglected.Concurrently,regardless of wet or dry conditions,disturbance of the heat transport by conduction caused by rainfall is stronger than that of convection by liquid water.In addition,when rainfall decreases by 1.5 times(212 mm)and increases by 1.5 times(477 mm),the thickness of the active layer increases by 0.12 m and decreases by 0.21 m,respectively.The results show that dry conditions are not conducive to the preservation of frozen soil;however,wet conditions are conducive to the preservation of frozen soil,although there is a threshold value.When this threshold value is exceeded,rainfall is unfavourable for the development of frozen soil.展开更多
Based on salt-frost heave tests of sulfate saline soil under repeated freeze−thaw cycles,this paper discusses the mechanism of the salt-frost heave under long-term freeze−thaw cycles.The results show that the salt-fro...Based on salt-frost heave tests of sulfate saline soil under repeated freeze−thaw cycles,this paper discusses the mechanism of the salt-frost heave under long-term freeze−thaw cycles.The results show that the salt-frost heave can be restricted considerably by loads,and there is a critical load for the salt-frost heave cumulative effect.Under this load,peak values of salt-frost heave approach a constant,and the residual values become 0.There is no longer structure heave or cumulative effect of saline soil exposed to freeze−thaw cycles under the critical load.Taking cumulative effect into account in calculations of salt-frost heave,a salt-frost heave model under freeze−thaw cycles is developed.展开更多
基金supported by the National Natural Science Foun-dation of China(12362032)the Key Research and Development Pro-gram of Gansu Province-Social Development(23YFFA0063).
文摘In order to explore the mechanical properties and microstructure changes of frozen saline silty clay in the Hexi region of Gansu Province,triaxial compression tests and scanning electron microscopy(SEM)analysis experiment were conducted to explore the effects of moisture content,confining pressure,and temperature on the stress-strain characteristics and failure modes of frozen soil,as well as the changes in the internal microstructure of the sample.The experimental results show that the strength of frozen sulfate saline soil first increases and then decreases with the increase of moisture content,and the maximum strength corresponds to a moisture content of 15%.The changes in confining pressure and strength have the same trend.The lower the temperature,the greater the strength of the sample.During the entire loading process,the specimens undergo a gradual transition from volume shrinkage to volume expansion.Due to the strain harden behavior of the stress-strain curve throughout the entire loading process,the failure mode of the specimens is plastic failure.The internal microstructure of the sample gradually transitions from point-point contact and edge-point contact before shearing to edge-surface contact and edge-edge contact after shearing,and the pore size inside the sample increases after shearing,with a loose arrangement of the particle skeleton.The above research conclusions can lay a certain theoretical foun-dation for the engineering design and construction of sulfate saline soil in cold and arid areas.
基金Project supported by the National Natural Science Foundation of China(Nos.51368038 and11162008)the Alumni Foundation of Civil Engineering of Lanzhou University of Technology(No.TM-QK-0701)the Environmental Protection Department of Gansu Province of China(No.GSEP-2014-23)
文摘The capillary interactions, including the capillary force and capillary suction, between two unequal-sized particles with a fixed liquid volume are investigated. The cap- illary interaction model is used within the Young-Laplace framework. With the profile of the meridian of the liquid bridge, the capillary suction, and the liquid volume as state variables, the governing equations with two-fixed-point boundary axe first derived using a variable substitution technique, in which the gravity effects are neglected. The capillary suction and geometry of the liquid bridge with a fixed volume are solved with a shooting method. In modeling the capillary force, the Gorge method is applied. The effects of var- ious parameters including the distance between two particles, the ratio of particle radii, and the liquid-solid contact angles are discussed.
基金funded by the National Natural Science Foundation of China(No.42261028,No.41961010,No.41801033)the"Light of West China"Program for the Organization Department of the Central Committee of the CPC,etc.(Zhang Mingli)+2 种基金the Chinese Academy of Sciences"Light of West China"Program for Western Young ScholarsIndustrial support program of higher education of Gansu province(2020C-40)Basic Research Innovation Group of Gansu province(20JR5RA478)
文摘The amount of rainfall varies unevenly in different regions of the Qinghai-Tibet Plateau,with some regions becoming wetter and others drier.Precipitation has an important impact on the process of surface energy balance and the energy-water transfer within soils.To clarify the thermal-moisture dynamics and thermal stability of the active layer in permafrost regions under wet/dry conditions,the verified water-vapour-heat coupling model was used.Changes in the surface energy balance,energy-water transfer within the soil,and thickness of the active layer were quantitatively analyzed.The results demonstrate that rainfall changes significantly affect the Bowen ratio,which in turn affects surface energy exchange.Under wet/dry conditions,there is a positive correlation between rainfall and liquid water flux under the hydraulic gradient;water vapour migration is the main form under the temperature gradient,which indicates that the influence of water vapour migration on thermalmoisture dynamics of the active layer cannot be neglected.Concurrently,regardless of wet or dry conditions,disturbance of the heat transport by conduction caused by rainfall is stronger than that of convection by liquid water.In addition,when rainfall decreases by 1.5 times(212 mm)and increases by 1.5 times(477 mm),the thickness of the active layer increases by 0.12 m and decreases by 0.21 m,respectively.The results show that dry conditions are not conducive to the preservation of frozen soil;however,wet conditions are conducive to the preservation of frozen soil,although there is a threshold value.When this threshold value is exceeded,rainfall is unfavourable for the development of frozen soil.
基金the General project of Chongqing Science and Technology Commission Scientific(Grant No.cstc2019jcyj-msxmX0813)Youth Program of Scientific and Technological Innovation Fund of Gansu Academy of Sciences(Grant No.2019QN-04)and is a part of the Scientific Project of Yangtze Normal University(Grant No.2017 XJQN16).
文摘Based on salt-frost heave tests of sulfate saline soil under repeated freeze−thaw cycles,this paper discusses the mechanism of the salt-frost heave under long-term freeze−thaw cycles.The results show that the salt-frost heave can be restricted considerably by loads,and there is a critical load for the salt-frost heave cumulative effect.Under this load,peak values of salt-frost heave approach a constant,and the residual values become 0.There is no longer structure heave or cumulative effect of saline soil exposed to freeze−thaw cycles under the critical load.Taking cumulative effect into account in calculations of salt-frost heave,a salt-frost heave model under freeze−thaw cycles is developed.
