Determining Hydraulic Conductivity for Air-Filled Porosity in an Unsaturated Frozen Soil by the Multistep Outflow Method

2013 ◽  
Vol 12 (1) ◽  
pp. vzj2012.0061 ◽  
Author(s):  
Ying Zhao ◽  
Taku Nishimura ◽  
Robert Hill ◽  
Tsuyoshi Miyazaki
Keyword(s):  
Hydraulic Conductivity ◽  
Frozen Soil ◽  
Multistep Outflow

scholarly journals Performance of infiltration swales with regard to operation in winter times in an Alpine region

2011 ◽  
Vol 63 (11) ◽  
pp. 2658-2665 ◽  
Author(s):  
Stefan Fach ◽  
Carolina Engelhard ◽  
Nina Wittke ◽  
Wolfgang Rauch
Keyword(s):  
Soil Moisture ◽  
Hydraulic Conductivity ◽  
Fine Particles ◽  
Soil Column ◽  
Alpine Region ◽  
Frozen Soil ◽  
Cold Climate ◽  
National Guidelines ◽  
Winter Conditions ◽  
Parking Place

In cold climate regions winter conditions significantly influence the performance of stormwater infiltration devices. Frozen soil and water storage by snow changes their operation. In this paper winter operation of a grassed infiltration swale was investigated using on-site and laboratory measurements. The field investigation of a grassed swale at a parking place in an Alpine region showed that the swale fulfilled its function properly. Although the top layer was frozen for some time, the storage capacity of the swale was sufficient to store the precipitation until the conditions improved. The soil attenuated the air temperature, at 20 cm below ground surface the soil was only frozen for one week. Winter maintenance proved to be a problem, together with the snow from the parking place a lot of gravel and fine particles were deposited at one end of the swale. This decreased the hydraulic conductivity at that point significantly. The laboratory tests with soil columns showed an increase of flow time through the soil column with decreasing soil moisture content. For soil temperatures below 0 °C the hydraulic conductivity was reduced for increasing initial soil moisture contents. All in all the hydraulic conductivity was best around 0 °C for all soil water contents. However, also at minus 5 °C the coefficient of hydraulic conductivity was always at least above 10−6 m/s, thus within the range of tolerated hydraulic conductivity specified in the national guidelines. Nevertheless, the handling of the soil was found to have high influence on the results. The results indicate that in the Alpine region infiltration swales operate sufficiently under winter conditions although with decreased performance.

scholarly journals A Fractal Model of Hydraulic Conductivity for Saturated Frozen Soil

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 369 ◽  
Author(s):  
Lei Chen ◽  
Dongqing Li ◽  
Feng Ming ◽  
Xiangyang Shi ◽  
Xin Chen
Keyword(s):  
Hydraulic Conductivity ◽  
Pore Structure ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Fractal Theory ◽  
Frozen Soil ◽  
Soil Freezing ◽  
Size Dimension ◽  
Maximum Pore Size

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.

Hydraulic Conductivity Measurement for Three Frozen and Unfrozen Soils in the Red River of the North Basin

2021 ◽  
Vol 64 (3) ◽  
pp. 761-770
Author(s):  
Debjit Roy ◽  
Xinhua Jia ◽  
Xuefeng Chu ◽  
Jennifer M. Jacobs
Keyword(s):  
Hydraulic Conductivity ◽  
Sandy Loam ◽  
Field Capacity ◽  
Frozen Soil ◽  
Red River ◽  
Silty Clay ◽  
Frozen Soils ◽  
Soil Hydraulic Conductivity ◽  
The North ◽  
Soil Hydraulic

HighlightsHydraulic conductivity was measured in frozen and unfrozen soil conditions by a minidisk infiltrometer.In the RRB, frozen sandy loam and silty clay soils had the highest and lowest hydraulic conductivity, respectively.Three simple equations were developed for the three soils to predict frozen soil hydraulic conductivity.Freeze-thaw cycles reduced soil hydraulic conductivity.Abstract. Hydraulic conductivity (k) is a key parameter in describing water movement through a soil profile. In the Red River of the North basin (RRB), the hydraulic properties of frozen soils vary with temperature, water content, and other factors. In this study, a minidisk infiltrometer was used to measure the k values of three soils from the RRB: Colvin silty clay loam, Fargo silty clay, and Hecla sandy loam. The k values were measured for frozen and unfrozen soils with five different initial soil water contents: oven dry, permanent wilting point, field capacity, midway between permanent wilting point and field capacity, and saturation. The results showed that the mean k value of a frozen soil increased with an increase in initial soil water contents. Hecla soil had the highest k values and Fargo soil had the lowest k values for frozen soils. Three equations were fitted with the measured k values of Colvin silty clay loam, Fargo silty clay, and Hecla sandy loam soils. The k values were also estimated using the Motovilov model. When evaluating model performance, the fitted regression models agreed more closely with the measured k values (index of agreement, d, values of 0.96, 0.94, and 0.94 for Colvin, Fargo, and Hecla soils, respectively) than Motovilov models. Based on overall considerations of statistical measures, the fitted regression models predicted the k values better than Motovilov models for all three frozen soils. It was also found that the k values decreased with an increase in the number of the freeze and thaw cycles that changed the soil properties. Keywords: Frozen soil, Hydraulic conductivity, Mini disk infiltrometer, Red River Valley.

Influence of overconsolidation on the freezing characteristics of a clayey silt

1989 ◽  
Vol 26 (1) ◽  
pp. 9-21 ◽  
Author(s):  
J.-M. Konrad
Keyword(s):  
Hydraulic Conductivity ◽  
Void Ratio ◽  
Moisture Transfer ◽  
Frozen Soil ◽  
Frost Heave ◽  
Unfrozen Water ◽  
Initial Void Ratio ◽  
Clayey Silt ◽  
Segregation Potential ◽  
Lens Formation

Laboratory freezing tests were performed on a saturated clayey silt at various overconsolidation ratios (OCR) to establish the relationship between initial void ratio and stress history, and the amount of moisture transfer during freezing. The frost heave tests were analysed in terms of the segregation potential as well as a function of the temperature of ice lens formation and the overall hydraulic conductivity of the frozen fringe. All other factors being the same, the segregation potential was found to increase with increasing values of OCR (decreasing initial void ratios). However, the combined effects of decreasing void ratio and increasing suction at the frost line, all other factors being identical in all freezing tests, resulted in decreasing segregation potentials. This trend was the result of a decrease in the temperature of ice lens formation and the concomitant decrease in overall hydraulic conductivity of the frozen fringe. A simple model showed that the capillary unfrozen water between clay particles increases when the particles pack closer together, as overconsolidation increases, allowing the migratory water to freeze within the frozen soil at a colder temperature. Key words: frost heave, clayey silt, overconsolidation, void ratio.

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