Theoretical Analysis on Reduction of Load-Induced Excess Pore-Water Pressures in Roads with Geogrids
Publication: International Journal of Geomechanics
Volume 22, Issue 10
Abstract
Geogrids used in roads can not only stabilize granular bases on weak subgrade but also have the potential to reduce excess pore-water pressures and deformations in road layers under traffic loading. In this paper, the solution for the geogrid-stabilized two-layered saturated soil system was derived according to the layered elastic theory and the Biot consolidation theory, and considering the benefits of geogrids. In the derivation, the lateral confinement and tensioned membrane effects of the geogrid were expressed as external stresses applied at the interface as continuity conditions. The effect of the geogrid on suppressing excess pore-water pressures in roads was characterized along the depth. Due to the generation of pore-water pressure, the instant total vertical and radial stresses were higher than those calculated by the Burmister solution without considering pore-water pressure, while the instant vertical strains/displacements were lower than those calculated by the Burmister solution due to the reduction of the effective stresses. The inclusion of the geogrid reduced the pore-water pressure so that the deterioration of the road could be mitigated. The calculations using the proposed solution also showed that the reduction of the pore-water pressure was significant near the location of the geogrid.
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Data Availability Statement
All data, models, or codes that support the findings of this study are available from the corresponding author upon reasonable request.
Acknowledgments
This study was financially supported by the National Natural Science Foundation of China (Grant Nos. 52179108 and 51809172), the Natural Science Foundation of Guangdong Province (Grant No. 2019A1515011660), and the Fundamental Research Program of Qinghai Province (Grant No. 2020-ZJ-738).
Notation
The following symbols are used in this paper:
- A1–A3
- unknown variant;
- a
- radius of the applied pressure;
- B1–B3
- unknown variant;
- c
- parameter regarding M and k;
- E
- elastic modulus;
- Eb
- elastic modulus of base course;
- Eg
- elastic modulus of geogrid;
- Eghg
- geogrid stiffness;
- Es
- elastic modulus of subgrade;
- e
- volumetric strain;
- f(r, z, t)
- function;
- Laplace-Hankel transform of a function f(r, z, t);
- G
- shear modulus;
- h
- thickness of base course;
- hg
- thickness of geogrid;
- J0
- Bessel function in Order 0;
- J1
- Bessel function in Order 1;
- k
- permeability of soil;
- M
- parameter regarding shear modulus and Poisson’s ratio;
- m
- order of the Hankel transform;
- Nr
- tensile force of the geosynthetic in the radial direction;
- Nφ
- tensile force of the geosynthetic in the transverse direction;
- p
- applied pressure;
- Q
- volume of water through a unit area;
- q
- parameter;
- qzg
- vertical support stress provided by geogrid;
- r
- radial distance from the centerline;
- rd
- distance from the centerline to the inflection point;
- s
- transformed variant of t;
- srg
- lateral confinement stress provided by geogrid;
- t
- time;
- u
- lateral elastic displacement of soil;
- u*
- permanent lateral deformation of a road layer that mobilizes a geogrid;
- V1–V30
- parameters;
- w
- vertical elastic displacement of soil;
- w*
- permanent vertical deformation of a road layer that mobilizes a geogrid;
- z
- vertical distance from the interface;
- β
- stress distribution angle;
- γw
- unit weight of water;
- δ
- vertical displacement of geogrid;
- ɛ
- vertical strain;
- ɛ
- vertical permanent strain at the bottom of the base course;
- η
- reduction factor;
- λe
- elastic coefficient;
- λp
- plastic coefficient;
- μ
- Poisson’s ratio;
- μg
- Poisson’s ratio of geogrid;
- ξ
- transformed variant of r;
- σ
- excess pore pressure;
- σb
- excess pore pressure at the bottom of the base course;
- σr
- total normal stresses in the vertical direction;
- effective normal stresses in the radial direction;
- Laplace–Hankel transformed component of radial stress in Order zero;
- Laplace–Hankel transformed component of radial stress in Order 1;
- σs
- excess pore pressure at the top of the subgrade;
- σs,max
- maximum vertical stress at the top of the subgrade;
- σz
- total normal stresses in the transverse direction;
- effective normal stresses in the vertical direction;
- effective normal stresses at the bottom of the base course;
- effective normal stresses at the top of the subgrade;
- total normal stresses in the radial direction;
- effective normal stresses in the transverse direction;
- τzr
- shear stress;
- τrb
- shear stress at the bottom of the base course;
- τrs
- shear stress at the top of the subgrade;
- Laplacian operator for the axisymmetric problem;
- subscript of s
- parameters regarding subgrade;
- subscript of b
- parameters regarding base course; and
- subscript of g
- parameters regarding geogrid.
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© 2022 American Society of Civil Engineers.
History
Received: Jul 30, 2021
Accepted: Apr 24, 2022
Published online: Jul 20, 2022
Published in print: Oct 1, 2022
Discussion open until: Dec 20, 2022
ASCE Technical Topics:
- Continuum mechanics
- Design (by type)
- Dynamics (solid mechanics)
- Engineering fundamentals
- Engineering mechanics
- Geogrids
- Geomaterials
- Geomechanics
- Geotechnical engineering
- Highway and road management
- Highway transportation
- Highways and roads
- Infrastructure
- Layered soils
- Load factors
- Pore pressure
- Pore water
- Pressure (type)
- Soil mechanics
- Soils (by type)
- Solid mechanics
- Static loads
- Statics (mechanics)
- Structural design
- Traffic analysis
- Traffic engineering
- Transportation engineering
- Vertical loads
- Water (by type)
- Water and water resources
- Water management
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