This page has only limited features, please log in for full access.
Hydraulic conductivity of frozen soil is indispensable for describing water flow process in freezing soils. However, this conductivity is difficult to measure in the laboratory. So, the objective of this study is to propose a simple and smooth hydraulic conductivity model for saturated frozen soil based on the soil freezing characteristic curve (SFCC). Considering that the volume of pore water approximately represents the pore volume, the distribution of effective pore radii changed as a function of temperature was determined by combining the SFCC and the Gibbs–Thomson equation. Based on the distribution of effective pore radii, Hagen-Poiseuille equation, Darcy’s law, relative hydraulic conductivity and tortuosity, a simple and smooth hydraulic conductivity model for saturated frozen soil based on the SFCC was proposed. To illustrate the model performance, eight existing experimental cases were analyzed. The results showed that predictions considering the three different tortuosity formulations were in good agreement with the tested data; the results were worse when not considering the tortuosity and the results were best when considering the tortuosity τF=B/rb2. Moreover, the predictive modeling power was related to the tortuosity function. Furthermore, the model was further compared with the previous models, the results of which showed the better performance of the proposed model. The model is quite simple and timesaving to use when the SFCC and the saturated hydraulic conductivity are available. This result provides a new idea for developing the hydraulic conductivity model of saturated frozen soil.
Xiyan Zhang; Dongqing Li; Lei Chen; Feng Ming; Yuhang Liu. A new integral model for predicting the hydraulic conductivity of saturated frozen soil. Journal of Hydrology 2021, 603, 126838 .
AMA StyleXiyan Zhang, Dongqing Li, Lei Chen, Feng Ming, Yuhang Liu. A new integral model for predicting the hydraulic conductivity of saturated frozen soil. Journal of Hydrology. 2021; 603 ():126838.
Chicago/Turabian StyleXiyan Zhang; Dongqing Li; Lei Chen; Feng Ming; Yuhang Liu. 2021. "A new integral model for predicting the hydraulic conductivity of saturated frozen soil." Journal of Hydrology 603, no. : 126838.
Ice lens is the key factor which determines the frost heave in engineering construction in cold regions. At present, several theories have been proposed to describe the formation of ice lens. However, most of these theories analyzed the ice lens formation from a macroscopic view and ignored the influence of microscopic pore sizes and structures. Meanwhile, these theories lacked the support of measured data. To solve this problem, the microscopic crystallization stress was converted into the macro mean stress through the principle of statistics with the consideration of pore size distribution. The mean stress was treated as the driving force of the formation of ice lens and induced into the criterion of ice lens formation. The influence of pore structure and unfrozen water content on the mean stress was analyzed. The results indicate that the microcosmic crystallization pressure can be converted into the macro mean stress through the principle of statistics. Larger mean stress means the ice lens will be formed easier in the soil. The mean stress is positively correlated with initial water content. At the same temperature, an increase to both the initial water content and the number of pores can result in a larger mean stress. Under the same initial water content, mean stress increases with decreasing temperature. The result provides a theoretical basis for studying ice lens formation from the crystallization theory.
Yuhang Liu; Dongqing Li; Lei Chen; Feng Ming. Study on the Mechanical Criterion of Ice Lens Formation Based on Pore Size Distribution. Applied Sciences 2020, 10, 8981 .
AMA StyleYuhang Liu, Dongqing Li, Lei Chen, Feng Ming. Study on the Mechanical Criterion of Ice Lens Formation Based on Pore Size Distribution. Applied Sciences. 2020; 10 (24):8981.
Chicago/Turabian StyleYuhang Liu; Dongqing Li; Lei Chen; Feng Ming. 2020. "Study on the Mechanical Criterion of Ice Lens Formation Based on Pore Size Distribution." Applied Sciences 10, no. 24: 8981.
Knowledge of the hydraulic conductivity of warm frozen soil is crucial for accurately calculating the deformation of buildings built in permafrost, and the objective of this study is to provide an experimental and theoretical method for obtaining the hydraulic conductivity of warm saturated frozen soil. The permeability experiments were carried out on warm frozen soil in the low temperature rock triaxial testing system, which provides a precise measurement of the water flow rate through the warm frozen soil. Repeated experiments were conducted to verify the validity of the experimental results. Subsequently, based on the experimental results and given the shortcomings of the ice impedance model, the equivalent model was proposed to predict the hydraulic conductivity of saturated frozen soil. The model suggested that saturated frozen soil and unsaturated unfrozen soil with the same liquid water content have the same hydraulic conductivity. To illustrate the validity of the model, the predictions of seven hydraulic conductivity models for unsaturated unfrozen soil were compared with the measured hydraulic conductivity of saturated frozen soil. The results show that the predictions are close to the measured data, which shows the validity of the model. Thus, the hydraulic conductivity of saturated frozen soil can be directly predicted by the hydraulic conductivity model for unsaturated unfrozen soil. The results provide a new method for obtaining the hydraulic conductivity of saturated frozen soil, which can provide a reference for the design and construction of buildings built in permafrost.
Lei Chen; Feng Ming; Xiyan Zhang; Xiaobin Wei; Yuhang Liu. Comparison of the hydraulic conductivity between saturated frozen and unsaturated unfrozen soils. International Journal of Heat and Mass Transfer 2020, 165, 120718 .
AMA StyleLei Chen, Feng Ming, Xiyan Zhang, Xiaobin Wei, Yuhang Liu. Comparison of the hydraulic conductivity between saturated frozen and unsaturated unfrozen soils. International Journal of Heat and Mass Transfer. 2020; 165 ():120718.
Chicago/Turabian StyleLei Chen; Feng Ming; Xiyan Zhang; Xiaobin Wei; Yuhang Liu. 2020. "Comparison of the hydraulic conductivity between saturated frozen and unsaturated unfrozen soils." International Journal of Heat and Mass Transfer 165, no. : 120718.
Engineering practices illustrate that the water phase change in soil causes severe damage to roads, canals, airport runways and other buildings. The freezing point is an important indicator to judge whether the soil is frozen or not. Up to now, the influence of salt on the freezing point is still not well described. To resolve this problem, a series of freezing point tests for saline soil were conducted in the laboratory. Based on the relationship between the freezing point and the water activity, a thermodynamic model considering the excess Gibbs energy was proposed for predicting the freezing point of saline soil by inducing the UNIQUAC (universal quasi-chemical) model. The experimental results show that the initial water content has little influence on the freezing point if the initial water content is higher than the critical water content, while the freezing point decreases with the decrease of the water content if the initial water content is lower than the critical water content. Moreover, it is found that the freezing point is related to the energy status of liquid water in saline soils and it decreases with the increase of the salt concentration. Moreover, the freezing point depression of saline soil is mainly caused by the decrease of water activity. Compared with the other two terms, the residual term, accounting for the molecular interactions, has an obvious influence on the water activity. This result is helpful for understanding how salt concentration affects the freezing point of saline soil and provides a reference for engineering construction in saline soil areas.
Feng Ming; Lei Chen; Dongqing Li; Chengcheng Du. Investigation into Freezing Point Depression in Soil Caused by NaCl Solution. Water 2020, 12, 2232 .
AMA StyleFeng Ming, Lei Chen, Dongqing Li, Chengcheng Du. Investigation into Freezing Point Depression in Soil Caused by NaCl Solution. Water. 2020; 12 (8):2232.
Chicago/Turabian StyleFeng Ming; Lei Chen; Dongqing Li; Chengcheng Du. 2020. "Investigation into Freezing Point Depression in Soil Caused by NaCl Solution." Water 12, no. 8: 2232.
Buildings built in the permafrost regions are always subjected to frost heave and thawing settlement deformation, which is mainly attributed to changes in foundation soil properties with environmental temperature, especially the hydraulic conductivity of warm frozen soil. To investigate the influence of the temperature on hydraulic conductivity, this study presented a model for predicting the hydraulic conductivity of warm frozen soil. Based on the discontinuous noncircular capillary bundle model, the expression of the hydraulic conductivity of the unsaturated soil was derived with the modified Hagen- Poiseuille equation, the Kelvin equation, the Campbell model for the matric potential and the Darcy's law. Then, based on the assumption that water transport in saturated frozen soil behaves with the same process as that in unsaturated unfrozen soil, the hydraulic conductivity model for warm frozen soil was proposed. To assess the predictive power of the proposed model, the predicted and tested hydraulic conductivities of eight different sets of soil were compared. The comparison results suggest that the proposed model performs well for the tested data. The results suggest that the hydraulic conductivity of warm frozen soil is mainly determined by the unfrozen water content, which is controlled by the temperature and soil particle size distribution. The proposed model is simple in the mathematical formula and readily integrated into frost heave and thawing settlement models. In addition, the model shows the relationship of hydraulic conductivity between saturated frozen soil and unsaturated unfrozen soil.
Lei Chen; Xiyan Zhang. A model for predicting the hydraulic conductivity of warm saturated frozen soil. Building and Environment 2020, 179, 106939 .
AMA StyleLei Chen, Xiyan Zhang. A model for predicting the hydraulic conductivity of warm saturated frozen soil. Building and Environment. 2020; 179 ():106939.
Chicago/Turabian StyleLei Chen; Xiyan Zhang. 2020. "A model for predicting the hydraulic conductivity of warm saturated frozen soil." Building and Environment 179, no. : 106939.
Electrical resistivity of soil has become one of the most important indicators of compactness and compressive resistance. In previous studies, the temperature of soil tested was always above 0°C. However, due to the phase change of pore water, the resistivity of freezing soils are different from that of unfrozen soils. Therefore, it is necessary to clarify the influence of temperature on electrical resistivity. To achieve this goal, according to the bundle of the cylindrical capillary model, pores in soil were treated as conducting tubes, and two simple log‐normal functions were introduced to describe the distribution of the conducting tubes. Based on the conductivity theory, a new model considering the temperature and the pore size distribution was presented. Results show that only a part of the conducting tubes can be treated as the effective conducting tubes, which are determined by the soil temperature. Furthermore, a small portion of the pores with the smaller size controlled the electrical resistivity of the freezing clay. In other words, the change in the electrical resistivity of freezing clay was caused mainly by the change of unfrozen water content through the decrease in temperature. Based on the experimental results conducted on clay from Northeast China, the validity of the presented model was verified. The comparison results indicate that there was a good agreement between the calculated results and the experimental results. To expand the scope of the model, more laboratory tests are suggested to conduct to verify the applicability of the model to other clays.
F. Ming; D. Q. Li; Lei Chen. Electrical Resistivity of Freezing Clay: Experimental Study and Theoretical Model. Journal of Geophysical Research: Earth Surface 2020, 125, 1 .
AMA StyleF. Ming, D. Q. Li, Lei Chen. Electrical Resistivity of Freezing Clay: Experimental Study and Theoretical Model. Journal of Geophysical Research: Earth Surface. 2020; 125 (2):1.
Chicago/Turabian StyleF. Ming; D. Q. Li; Lei Chen. 2020. "Electrical Resistivity of Freezing Clay: Experimental Study and Theoretical Model." Journal of Geophysical Research: Earth Surface 125, no. 2: 1.
Negative temperature curing is a very harmful factor for geopolymer mortar or concrete, which will decrease the strength and durability. The water in the geopolymer mixture may be frozen into ice, and the water content is a crucial factor. The purpose of this paper is to explore the influence of water content on the properties of alkali-activated binders mortar cured at −5 °C. Fly ash (FA) and ground granulated blast furnace slag (GGBFS) were used as binders. Three groups of experiments with different water content were carried out. The prepared samples were investigated through uniaxial compression strength test, Scanning electron microscopy (SEM), and X-ray diffraction (XRD) for the determination of their compressive strength, microstructural features, phase, and composition. The results indicated that, the compressive strength of samples basically maintained 25.78 MPa–27.10 MPa at an age of 28 days; for 90 days, the values reached 33.4 MPa–34.04 MPa. The results showed that lower water content is beneficial to improving the early strength of mortar at −5 °C curing condition, while it has little impact on long-term strength. These results may provide references for the design and construction of geopolymer concrete in cold regions.
Xiaobin Wei; Feng Ming; Dongqing Li; Lei Chen; Yuhang Liu. Influence of Water Content on Mechanical Strength and Microstructure of Alkali-Activated Fly Ash/GGBFS Mortars Cured at Cold and Polar Regions. Materials 2019, 13, 138 .
AMA StyleXiaobin Wei, Feng Ming, Dongqing Li, Lei Chen, Yuhang Liu. Influence of Water Content on Mechanical Strength and Microstructure of Alkali-Activated Fly Ash/GGBFS Mortars Cured at Cold and Polar Regions. Materials. 2019; 13 (1):138.
Chicago/Turabian StyleXiaobin Wei; Feng Ming; Dongqing Li; Lei Chen; Yuhang Liu. 2019. "Influence of Water Content on Mechanical Strength and Microstructure of Alkali-Activated Fly Ash/GGBFS Mortars Cured at Cold and Polar Regions." Materials 13, no. 1: 138.
Knowledge of hydraulic conductivity is crucial for determining water movement in frozen soil, and the objective of this study is to introduce the soil freezing characteristic curve to estimate the hydraulic conductivity of saturated frozen soil. Based on the non-uniform tortuous capillary bundle model and the assumption that the ice was first formed in the pores with largest size, a physical infiltration model of saturated frozen soil was developed. On the basis of this physical infiltration model, a new approach for estimating the hydraulic conductivity of saturated frozen soil was developed by using the Hagen-Poiseuille equation and Darcy's law. To verify the validity of this approach, five soil data sets, including 29 data points with hydraulic conductivity between 10−6 cm/s and 10−11 cm/s, were used to compare the predicted results and experimental data. The results show that the new approach fits the experimental data well. This approach is more convenient than the soil water characteristic curve in numerical modeling, and it can be used to describe the relationship between hydraulic conductivity and minus temperature. Moreover, the new approach and the results in this study maybe also can provide a reference for the research on water flow and the related numerical modeling in cold regions environmental engineering.
Feng Ming; Lei Chen; Dongqing Li; Xiaobin Wei. Estimation of hydraulic conductivity of saturated frozen soil from the soil freezing characteristic curve. Science of The Total Environment 2019, 698, 134132 .
AMA StyleFeng Ming, Lei Chen, Dongqing Li, Xiaobin Wei. Estimation of hydraulic conductivity of saturated frozen soil from the soil freezing characteristic curve. Science of The Total Environment. 2019; 698 ():134132.
Chicago/Turabian StyleFeng Ming; Lei Chen; Dongqing Li; Xiaobin Wei. 2019. "Estimation of hydraulic conductivity of saturated frozen soil from the soil freezing characteristic curve." Science of The Total Environment 698, no. : 134132.
In cold regions, hydraulic conductivity is a critical parameter for determining the water flow in frozen soil. Previous studies have shown that hydraulic conductivity hinges on the pore structure, which is often depicted as the pore size and porosity. However, these two parameters do not sufficiently represent the pore structure. To enhance the characterization ability of the pore structure, this study introduced fractal theory to investigate the influence of pore structure on hydraulic conductivity. In this study, the pores were conceptualized as a bundle of tortuous capillaries with different radii and the cumulative pore size distribution of the capillaries was considered to satisfy the fractal law. Using the Hagen-Poiseuille equation, a fractal capillary bundle model of hydraulic conductivity for saturated frozen soil was developed. The model validity was evaluated using experimental data and by comparison with previous models. The results showed that the model performed well for frozen soil. The model showed that hydraulic conductivity was related to the maximum pore size, pore size dimension, porosity and tortuosity. Of all these parameters, pore size played a key role in affecting hydraulic conductivity. The pore size dimension was found to decrease linearly with temperature, the maximum pore size decreased with temperature and the tortuosity increased with temperature. The model could be used to predict the hydraulic conductivity of frozen soil, revealing the mechanism of change in hydraulic conductivity with temperature. In addition, the pore size distribution was approximately estimated using the soil freezing curve, making this method could be an alternative to the mercury intrusion test, which has difficult maneuverability and high costs. Darcy’s law is valid in saturated frozen silt, clayed silt and clay, but may not be valid in saturated frozen sand and unsaturated frozen soil.
Lei Chen; Dongqing Li; Feng Ming; Xiangyang Shi; Xin Chen. A Fractal Model of Hydraulic Conductivity for Saturated Frozen Soil. Water 2019, 11, 369 .
AMA StyleLei Chen, Dongqing Li, Feng Ming, Xiangyang Shi, Xin Chen. A Fractal Model of Hydraulic Conductivity for Saturated Frozen Soil. Water. 2019; 11 (2):369.
Chicago/Turabian StyleLei Chen; Dongqing Li; Feng Ming; Xiangyang Shi; Xin Chen. 2019. "A Fractal Model of Hydraulic Conductivity for Saturated Frozen Soil." Water 11, no. 2: 369.