Quaternary silt is widely distributed in China and easily liquefies during earthquakes. To identify the influence of the dry density on the liquefaction behaviour of Quaternary silt, 40 cyclic triaxial liquefaction te...Quaternary silt is widely distributed in China and easily liquefies during earthquakes. To identify the influence of the dry density on the liquefaction behaviour of Quaternary silt, 40 cyclic triaxial liquefaction tests were performed on loose silt(dry density rd=1.460 g/cm^3) and dense silt(rd=1.586 g/cm^3) under different cyclic stress ratios(CSRs) to obtain liquefaction assessment criteria, determine the liquefaction resistance, improve the excess pore water pressure(EPWP) growth model and clarify the relationship between the shear modulus and damping ratio. The results indicate that the initial liquefaction assessment criteria for the loose and dense silts are a double-amplitude axial strain of 5% and an EPWP ratio of 1. The increase in the anti-liquefaction ability for the dense silt is more significant under lower confining pressures. The CSR of loose silt falls well within the results of the sandy silt and Fraser River silt, and the dense silt exhibits a higher liquefaction resistance than the sand-silt mixture. The relationships between the CSR and loading cycles were obtained at a failure strain of 1%. The EPWP development in the dense and loose silts complies with the "fast-stable" and "fast-gentle-sharp" growth modes, respectively. The power function model can effectively describe the EPWP growth characteristics of the dense silt. Finally, based on the liquefaction behaviour of silt, a suggestion for reinforcing silt slopes or foundations is proposed.展开更多
Determination of the wet-bulb temperature at the surface of a material is the basis of one class ofhumidity measuring instruments, and is important in industrial applications such as dryer modelling and simula-tion. T...Determination of the wet-bulb temperature at the surface of a material is the basis of one class ofhumidity measuring instruments, and is important in industrial applications such as dryer modelling and simula-tion. The psychrometer equation is a frequently used method of estimating wet-bulb temperature, and contains apsychrometer 'constant'. Analysis shows that this is in fact a variable coefficient affected by temperature, pressure,radiation and conduction effects, and the identity of the gas and vapour. Radiation and conduction affect the dif-ference between adiabatic saturation temperature and indicated wet-bulb temperature. Inconsistencies in currentlyrecommended values for the psychrometer coefficient, including published international standards, are identifiedand explained. Particular problems arise when the enhancement factor is applied to vapour pressure to accountfor non-ideality of gases. Special considerations are also needed for wet-bulb temperatures approaching the boilingpoint, where the psychrometer coefficient tends to zero. Self-consistent recommendations recently published in thenew British Standard BS1339 are given, which cover both the air-water system and a general vapour-gas system.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant No.41761144077)the CAS “Light of West China” Program (Grant No.Y6R2240240)+1 种基金the Key Research Program of Frontier Sciences,CAS (Grant No.QYZDB-SSW-DQC010)the Sichuan science and technology plan project (Grant No.2017JY0251)
文摘Quaternary silt is widely distributed in China and easily liquefies during earthquakes. To identify the influence of the dry density on the liquefaction behaviour of Quaternary silt, 40 cyclic triaxial liquefaction tests were performed on loose silt(dry density rd=1.460 g/cm^3) and dense silt(rd=1.586 g/cm^3) under different cyclic stress ratios(CSRs) to obtain liquefaction assessment criteria, determine the liquefaction resistance, improve the excess pore water pressure(EPWP) growth model and clarify the relationship between the shear modulus and damping ratio. The results indicate that the initial liquefaction assessment criteria for the loose and dense silts are a double-amplitude axial strain of 5% and an EPWP ratio of 1. The increase in the anti-liquefaction ability for the dense silt is more significant under lower confining pressures. The CSR of loose silt falls well within the results of the sandy silt and Fraser River silt, and the dense silt exhibits a higher liquefaction resistance than the sand-silt mixture. The relationships between the CSR and loading cycles were obtained at a failure strain of 1%. The EPWP development in the dense and loose silts complies with the "fast-stable" and "fast-gentle-sharp" growth modes, respectively. The power function model can effectively describe the EPWP growth characteristics of the dense silt. Finally, based on the liquefaction behaviour of silt, a suggestion for reinforcing silt slopes or foundations is proposed.
文摘Determination of the wet-bulb temperature at the surface of a material is the basis of one class ofhumidity measuring instruments, and is important in industrial applications such as dryer modelling and simula-tion. The psychrometer equation is a frequently used method of estimating wet-bulb temperature, and contains apsychrometer 'constant'. Analysis shows that this is in fact a variable coefficient affected by temperature, pressure,radiation and conduction effects, and the identity of the gas and vapour. Radiation and conduction affect the dif-ference between adiabatic saturation temperature and indicated wet-bulb temperature. Inconsistencies in currentlyrecommended values for the psychrometer coefficient, including published international standards, are identifiedand explained. Particular problems arise when the enhancement factor is applied to vapour pressure to accountfor non-ideality of gases. Special considerations are also needed for wet-bulb temperatures approaching the boilingpoint, where the psychrometer coefficient tends to zero. Self-consistent recommendations recently published in thenew British Standard BS1339 are given, which cover both the air-water system and a general vapour-gas system.
