Evaluation of Hydraulic Conductivity Functions of Saturated Soft Soils
Publication: International Journal of Geomechanics
Volume 20, Issue 11
Abstract
Hydraulic conductivities of soils rely significantly on three factors, the properties of their pore water, the relative quantity of their pore water, and changes in their pore structure. For saturated soft soils, that demonstrate a considerable degree of alteration in pore structure during densification, it is important to consider their volume change behavior when evaluating their transitional hydromechanical properties during evaporation. This paper reports on the evaluation of hydraulic conductivity functions (HCF) of two saturated soft soils using the evaporation method. The HCF of the samples will be established using the measurement of water loss and the associated gradient during evaporation. By recognizing the importance of the volume change behavior of deformable soft soils on their transitional hydromechanical properties, a theoretical formulation is suggested to incorporate their volume change behavior when estimating their transient hydraulic conductivities. An increase in the hydraulic conductivities of approximately one order of magnitude has been observed when volume change in the samples have been quantitatively considered in their calculation compared with cases when this type of effect is not considered. HCFs established using this approach, taking into consideration the volume change behavior of the samples, will be compared with those obtained through one-dimensional consolidation tests. The proposed method has the potential to provide HCF measurements at high void ratio ranges, where 1D consolidation tests would not be effective due to the highly fluidized condition of the material. Based on experimental results and analysis, this paper establishes a generalized theoretical formulation to appraise the hydraulic conductivity functions of deformable soft soils using the evaporation method and takes into consideration the volume change behavior of the sample.
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Acknowledgments
This work was funded by scholarship supports through the Australian Government Research Training Programme Scholarship (formerly the International Postgraduate Research Scholarship), UQ Centennial Scholarship (University of Queensland), and top up scholarship (School of Civil Engineering, University of Queensland) awarded to Mr. P. N. Mishra. We acknowledge the support from the Australian Research Council linkage project on “Engineering the strength and consolidation of reclaimed soft soil” awarded to Associate Professor Alexander Scheuermann. The support through the PoB/UQ research venture is gratefully acknowledged. We thank the anonymous reviewers for their time and suggestions to improve the manuscript.
Notation
The following symbols are used in this paper:
- A
- cross-sectional area for flow, evaporative cross-sectional area;
- A, B
- fitting parameters in Mesri and Olson (1971) model;
- A(w)
- evaporative cross-sectional area of the sample as a function of its gravimetric moisture content;
- Ao
- initial evaporative cross-sectional area of the sample;
- Aos
- initial cross-sectional area of the representative sample (shrinkage test);
- Ats
- cross-sectional area of the representative sample at a given time (shrinkage test);
- C, n
- fitting parameters Samarasinghe et al. (1982) model;
- d10
- particle diameter corresponding to 10% finer;
- d50
- particle diameter corresponding to 50% finer;
- d90
- particle diameter corresponding to 90% finer;
- e
- void ratio;
- f, Ats/Aos versus wts/wos
- nondimensional correlation between the gravimetric moisture content and the cross-sectional area of the representative sample (shrinkage test);
- g, Hts/Hos versus wts/wos
- nondimensional correlation between gravimetric moisture content and vertical stain of the representative sample (shrinkage test);
- Hos
- initial height of the representative sample (shrinkage test);
- i
- hydraulic gradient;
- K(w)
- hydraulic conductivity as a function of gravimetric moisture content
- K(θ)
- hydraulic conductivity as a function of volumetric moisture content;
- K(ψ)
- hydraulic conductivity as a function of soil water potential;
- K(ε)
- component of hydraulic conductivity resulting from consideration of the relative phasal movement;
- K(w, ε)
- hydraulic conductivity considering dependence on gravimetric moisture content and relative phasal movement;
- Q
- volumetric flow per unit time;
- q
- volumetric flux per unit time (Q/A);
- wos
- initial gravimetric moisture content of the representative sample (shrinkage test);
- wts
- gravimetric moisture content of the representative sample at a given time (shrinkage test);
- Z
- initial height of the evaporative flux measurement plane;
- z
- elevation head;
- ΔHts
- change in height of the representative sample at a given time (shrinkage test);
- ΔV/Δt
- volume of the water evaporated from the sample per unit time;
- vertical strain in the sample as a function of gravimetric moisture content (as a function of time) at time ti;
- θ
- volumetric moisture content;
- ψ
- pressure head;
- suction measured by the tensiometer at bottom and at time ti; and
- suction measured by the tensiometer at top and at time ti.
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History
Received: Jan 29, 2020
Accepted: Jul 9, 2020
Published online: Sep 11, 2020
Published in print: Nov 1, 2020
Discussion open until: Feb 11, 2021
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