Finite Hankel Transform Method–Based Analysis of Axisymmetric Free-Strain Consolidation Theory for Unsaturated Soils
Publication: International Journal of Geomechanics
Volume 23, Issue 11
Abstract
In this paper, the smear effect and the sand cushion that modifies the permeability of the top boundary are considered equivalently as semipermeable boundaries, to obtain an axisymmetric free-strain consolidation model for unsaturated soils capable of allowing for coupled radial–vertical flow under time-dependent loading. The semianalytical solution is then solved with finite Hankel transform and Laplace transform. This is also verified by comparison with two special cases of axisymmetric consolidation solutions in unsaturated soils. After analysis of the parameters, it is concluded that as the radial or vertical semipermeability factor increases, there is less impediment to the dissipation of excess pore pressures (EPPs); and when it takes values within 0.1–50, it can be used to simulate boundaries with arbitrary permeability from permeable to impermeable. The EPP distribution at different points and times reveals that the effect of the air- and water-phase semipermeability factor on the consolidation of unsaturated soil is different. Furthermore, the contour plots of EPP distribution under free-strain assumption provide a decent reflection of the smear effect and the alteration of the top boundary permeability due to the sand cushion.
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Data Availability Statement
All data, models, and codes generated or used during the study appear in the published article.
Acknowledgments
This research was supported by the National Natural Science Foundation of China (Grant No. 42072292).
Notation
The following symbols are used in this paper:
- Cw, Ca
- relevant water and air interaction coefficients (−);
- radial water and air coefficients of volume change (−);
- vertical water and air coefficients of volume change (−);
- load-related water and air interaction coefficients (−);
- g
- gravitational acceleration (∼9.807 m · s−2);
- thickness of the sand cushion and unsaturated soil layer (m);
- kar, kaz
- radial and vertical air permeability coefficients in the influence area (m/s);
- radial permeability coefficients of air and water in the smear zone (m/s);
- kat, kwt
- air and water permeability coefficients of the sand cushion (m/s);
- kwr, kwz
- radial and vertical water permeability coefficients in the influence area (m/s);
- M
- molecular mass of air (approximately 28.966 kg · kmol−1);
- coefficient of water and air volume changing with an increase in net normal stress (σz − ua) (kPa−1);
- coefficient of water and air volume changing with an increase in matric suction (ua − uw) (kPa−1);
- n0, Sr0
- initial porosity and degree of saturation (−);
- R
- molar air constant (approximately 8.314 J · mol−1 · K−1);
- vertical semipermeability factors of water and air (−);
- radial semipermeability factors of water and air (−);
- rd, rs, re
- radius of a vertical well, smear zone, and influence zone (m).
- T
- absolute temperature (=t0 + 273 K);
- uatm
- atmospheric pressure (approximately 101.3 kPa);
- uw, ua
- excess pore pressures of water and air phases (kPa);
- initial excess pore-water and pore-air pressures (kPa); and
- γw
- unit weight of water (approximately 9.8 kN · m−3).
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Received: Nov 16, 2022
Accepted: May 16, 2023
Published online: Aug 28, 2023
Published in print: Nov 1, 2023
Discussion open until: Jan 28, 2024
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