12 Sep 2022
12 Sep 2022
Status: this preprint is currently under review for the journal HESS.

Effects of dynamic changes of desiccation cracks on preferential flow: Experimental investigation and numerical modeling

Yi Luo1,2, Jiaming Zhang1, Zhi Zhou3, Juan P. Aguilar-Lopez4, Roberto Greco5, and Thom Bogaard2 Yi Luo et al.
  • 1Faculty of Engineering, China University of Geosciences (Wuhan), Wuhan, 430074, China
  • 2Water Resources Section, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, P.O. Box 5048, 2600 GA Delft, the Netherlands
  • 3Department of Engineering Management, Hubei University of Economics, Wuhan, 430205, China
  • 4Department of Hydraulic Engineering, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, 2600 GA, the Netherlands
  • 5Dipartimento di Ingegneria, Università degli Studi della Campania “Luigi Vanvitelli”, via Roma 29, 81031, Aversa, Italy

Abstract. Preferential flow induced by desiccation cracks (PF-DC) has been proven to be an important hydrological effect that could cause various geotechnical engineering and ecological environment problems. Investigation on the PF-DC remains a great challenge due to the soil shrinking-swelling behavior. This work presents an experimental and numerical study of the PF-DC considering the dynamic changes of DC. A soil column test was conducted under wetting-drying cycles to investigate the dynamic changes of DC and their hydrological response. The ratio between the crack area and soil matrix area (crack ratio), crack aperture and depth were measured. The soil water content, matrix suction and water drainage were monitored. A new dynamic dual-permeability preferential flow model (DPMDy) was developed, which includes physically-consistent functions in describing the variation of both porosity and hydraulic conductivity in crack and matrix domains. Its performance was compared to the single-domain model (SDM) and rigid dual-permeability model (DPM) with fixed crack ratio and hydraulic conductivity. The experimental results showed that the maximum crack ratio and aperture decreased when the evaporation intensity was excessively raised. The self-closure phenomenon of cracks and increased surficial water content were observed during low evaporation periods. The simulation results showed that the matrix evaporation modeled by the DPMDy is lower than that of the SDM and DPM, but its crack evaporation is the highest. Compared to the DPM, the DPMDy simulated a faster pressure head building-up process in the crack domain and higher water exchange rates from the crack to the matrix domain during rainfall. Using a fixed crack ratio in the DPM, whether it is the maximum or the average value from the experiment data, will overestimate the infiltration fluxes of PF-DC but underestimate its contribution to the matrix domain. In conclusion, the DPMDy better described the underlying physics involving crack evolution and hydrological response with respect to the SDM and DPM. Further improvement of the DPMDy should focus on the hysteresis effect of the SWRC curve and soil deformation during wetting-drying cycles.

Yi Luo et al.

Status: open (until 07 Nov 2022)

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Yi Luo et al.

Yi Luo et al.


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Short summary
This paper describes an experiment and modelling to the hydrological response of desiccation cracks under long-term wetting-drying cycles. We developed a new dynamic dual-permeability model to quantify the dynamic evolution of desiccation cracks and associated preferential flow and moisture distribution. Compared to other models, the dynamic dual-permeability model could describe the experimental data much better but also provided an improved description of the underlying physics.