Interpretation of water retention field measurements in relation to hysteresis phenomena

[1] A soil's capillarity, associated with the parameter sorptivity, is a dominant control on infiltration, particularly at the onset of rainfall or irrigation. Many mathematical models used to estimate sorptivity are only valid for dry soils. This paper examines how sorptivity and its capillary component (as wetting front potential) change with initial degree of saturation. We capture these effects with a simple modification to the classic Green-Ampt model of sorptivity. The modified model has practical applications, including (1) accurately describing the relative sorptivity of a soil at various water contents and (2) allowing for quantification of a soil's saturated hydraulic conductivity from sorptivity measurements, given estimates of the soil's characteristic curve and initial water content. The latter application is particularly useful in soils of low permeability, where the time required to estimate hydraulic conductivity through steady-state methods can be impractical.

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“…Using the common assumption that r ¼ 0 [Van Genuchten et al, 1991;Haverkamp et al, 2005;Canone et al, 2008], equation (15) can be rewritten as…”

Section: Nondimensional (Scaled) Sorptivitymentioning

confidence: 99%

Modeling effect of initial soil moisture on sorptivity and infiltration

et al. 2013

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“…In this procedure, it is assumed that

m

and

S_{w r}

are the same between the infiltration and drainage processes but that

α

is different. This assumption has been used in various models addressing the hysteresis in the P c ‐ S w relationship [ Kool and Parker , 1987; Luckner et al , 1989; Haverkamp et al , 2002; Canone et al , 2008]. Therefore, the only data required are the drainage P c ‐ S w curve of a water‐saturated sample, and the value of

{\overset{true¯}{S}}_{tot‐air}^{max}

for the use of .…”

Section: Theoretical Modelsmentioning

confidence: 99%

Size distributions of pore water and entrapped air during drying‐infiltration processes of sandstone characterized by water‐expulsion porosimetry

Nishiyama

Yokoyama

Takeuchi

2012

Water Resources Research

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.[1] The transport of pore water in a rock during drying-infiltration processes was characterized by water-expulsion porosimetry. In this method, pore water is expelled by increasing gas pressure in a stepwise fashion, and the amounts of water in each pore size class are determined. Fontainebleau sandstone, having an open porosity of 6% and main pore radii of 1-20 mm, was used. The change in size distribution of pore water was determined as a function of the degree of drying. As the drying proceeded, the amount of water decreased first in the larger pores followed by the smaller pores. Next, water was infiltrated into the sample preliminarily adjusted to various water saturations (S pre-flow ), and the entrapped air saturation, hydraulic conductivity (K), and size distribution of pore water were measured. As S pre-flow decreased, the entrapped air saturation increased and K decreased as approximated by K ! S flow 4.5 , where S flow is the water saturation after the infiltration. A comparison of the size distributions of pore water before and after the infiltration revealed that the ease of water infiltration (air entrapment) depends on pore size. If pores of >8 mm radii were emptied by drying, they were readily refilled with water, whereas smaller pores were only partially refilled because air was trapped in them. The experimentally measured K-S flow relationship generally agreed with those predicted by the Mualem-van Genuchten model and its modified version accounting for air entrapment, but some differences in the size distribution of pore water were observed between the experiment and the models.Citation: Nishiyama, N., T. Yokoyama, and S. Takeuchi (2012), Size distributions of pore water and entrapped air during dryinginfiltration processes of sandstone characterized by water-expulsion porosimetry, Water Resour. Res., 48, W09556,

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“…All hysteresis models can be implemented, no matter of a practical extrapolation model from the drying boundary or an interpolation model between both boundaries which would be available only in the lab. The huang's model can be displaced as other models like the method developed by Canone et al (2008). Besides, these two hysteresis models, huang's and Canone's models, both performed lower deviations than the others.…”

Section: Infiltration Modelmentioning

confidence: 99%

“…For the application in the field, a practical extrapolation model from the drying boundary is much more important than an interpolation model between both boundaries which would be available only in the lab. Therefore, the infiltration model referred to an excellent paper published by Canone et al (2008) in WRR and discussed. There are two types of soil-water retention data have been used to analyse: (1) literature data taken from the study by Dane and Hruska (1983) and Haverkamp et al (1997) and (2) field data collected at the experimental station of the Agricultural Faculty of the Universita' degli Studi di Torino at Grugliasco/Italy (Ferraris, 2007).…”

Section: Infiltration Modelmentioning

confidence: 99%

The influence of water retention curve hysteresis on the stability of unsaturated soil slopes

Tan

Chen

2011

Hydrological Processes

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Abstract:Hysteresis is a common feature exhibited in hydraulic properties of an unsaturated soil. The movement of wetting front and the hysteresis effect are important factors which impact the shear strength of the unsaturated soil and the mechanics of shallow landslides. These failures are mainly triggered by the deepening of the wetting front accompanied by a decrease in matric suction induced by infiltration. This research establishes a method for determining a stability analysis of unsaturated infinite soil slopes, integrating the influence of infiltration and the water retention curve hysteresis. Furthermore, the present stability analysis method including the infiltration model and the advanced Mohr-Coulomb failure criterion calculates the variations of the safety factor (FS) in accordance with different slope angle, depth and hydrological processes. The experimentally measured data on the effect of hysteresis are also carried out for comparison. Numerical analyses, employing both wetting and drying hydraulic behaviour of unsaturated soil, are performed to study the difference in soil-water content as observed in the experiments. The simulating approximations also fully responded to the experimental data of sand box. The results suggest that the hysteresis behaviour affect the distribution of soil-water content within the slope indeed. The hysteresis made the FS values a remarkable recovery during the period of non-rainfall in a rainfall event. The appropriate hydraulic properties of soil (i.e. wetting or drying) should be used in accordance with the processes that unsaturated soil actually experience. This method will enable us to acquire more accurate matric suction head and the unsaturated soil-shear strength as it changes with the hysteretic flow, in order to calculate into the stability analysis of shallow landslides. An advanced understanding of the process mechanism afforded by this method is critical to realizing a reliable and appropriate design for slope stabilization. It also offers some immediate reference information to the disaster reduction department of the government.

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Interpretation of water retention field measurements in relation to hysteresis phenomena

Cited by 26 publications

References 52 publications

Modeling effect of initial soil moisture on sorptivity and infiltration

Modeling effect of initial soil moisture on sorptivity and infiltration

Size distributions of pore water and entrapped air during drying‐infiltration processes of sandstone characterized by water‐expulsion porosimetry

The influence of water retention curve hysteresis on the stability of unsaturated soil slopes

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