Technical Papers
Jul 7, 2022

Stability Analysis of Inhomogeneous Slopes in Unsaturated Soils Optimized by a Genetic Algorithm

Publication: International Journal of Geomechanics
Volume 22, Issue 9

Abstract

Most theoretical analysis for the assessment of the stability of soil slopes is commonly performed under completely dry or saturated and homogeneous conditions, the effect of suction and soil inhomogeneity are generally ignored in stability assessments. This paper presents an analytical framework to investigate the stability of three-dimensional (3D) inhomogeneous slopes in unsaturated soils under one-dimensional steady flow. Based on the kinematic limit analysis method, a 3D rotational failure mechanism is adopted, and three possible failure mechanisms of soil slopes (e.g., toe, face, and base failure) are considered. A closed-form solution for the factor of safety is derived by the energy balance equation, which takes the effects of the suction stress, effective unit weight, and inhomogeneity of soil simultaneously into account. To improve optimize efficiency, a genetic algorithm (GA), which has the advantages of high efficiency and good accuracy, is applied to search for the minimum of the factor of safety of the slope. This methodology is well validated through comparison with existing solutions and numerical simulation. Parameter analyses are performed to investigate the effects of different parameters on slope stability. The results of the present study indicate that the stability of the slope will be underestimated if the suction stress and the change in effective unit soil weight are not considered. The inhomogeneity of soil can reduce the stability of slopes.

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Data Availability Statement

Some or all data, models, or codes that support the findings of this paper are available from the corresponding author upon reasonable request. To be specific, all data that support all the figures in this paper can be provided by the corresponding author.

Acknowledgments

The authors would like to thank the editor and the anonymous reviewers for their valuable suggestions to improve this paper. This research was supported by the National Natural Science Foundation of China (Grant No. 41807295). The financial support is greatly appreciated.

Notation

The following symbols are used in this paper:
a
distances from the centerline of the conical volume to the slope crest;
B
maximum width of the rotational failure mechanism;
Bmax
maximum width of the 3D portion;
b
width of plane insert block;
c
effective cohesion strength;
capp
apparent cohesion;
c0
effective cohesion strength of the slope base;
cf
effective cohesion strength of the slope face;
c3D and c2D
effective cohesion in 3D and 2D portions of slope, respectively;
Dc3D and Dc2D
rate of the internal energy dissipation of 3D and 2Ds portion achieved by soil cohesion, respectively;
Ds3D and Ds2D
rate of the internal energy dissipation of 3D and 2D portions achieved by apparent cohesion, respectively;
d
distances from the centerline of the conical volume to the slope face;
e
distance from the centerline of the conical volume to the slope base;
Fs
factor of safety of slope;
Gs
specific gravity of soil;
H
slope height;
H
auxiliary height of slope;
hf
distance from the slope face to the slope crest;
hs
distance from the slip face to the slope crest;
ks
saturated hydraulic conductivity;
n
distribution of the soil’s pore size;
nw and nd
pore size distribution parameter of wet and dry paths, respectively;
n0
inhomogeneous coefficient;
q
vertical steady flow rate;
R
radius of the conical volume;
r and r
radius of log spiral and inner log spiral, respectively;
r0 and r0
initial radius of log spirals OA and OA′, respectively;
rf
distance from the slope face to the center of rotation O;
rh
final radius of the log spiral;
rm
average radius of both spirals;
S
degree of pore water saturation;
Se
normalized degree of saturation;
Sr
residual degree of saturation;
(uauw)
matric suction;
ua
pore air pressure;
uw
pore water pressure;
Wγ3D and Wγ2D
rate of external forces achieved by the effective soil weight of the 3D and 2D parts, respectively;
Wγ3D, Wγ2D
rate of external forces achieved by the effective soil weight of the 3D and 2D parts, respectively;
z0
vertical distance from the water table to the slope toe elevation;
z3D
vertical distance from any one point of failure block to the water table level;
z2D
vertical distance from the point on the sliding surface of the plane insert block to the water table level;
α
inverse of air entry pressure;
αw and αd
inverse of air entry pressure of wet and dry paths, respectively;
β
slope inclination angle;
β
auxiliary slope inclination angle;
γ
effective unit soil weight;
γsat
unit weight of saturated soil;
γw
unit weight of water;
γH/c
stability factor of slope;
σ
total stress;
σ
effective stress;
σs
suction stress;
ϕ
effective internal friction angle;
τf
shear strength;
θ
rotational angle;
θ0
initial rotational angle;
θB and θc
rotational angles from horizontal line to the line that passes through points B and C, respectively;
θh
final rotational angle of log spiral;
θs
saturated volumetric water content; and
θr
residual volumetric water content.

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International Journal of Geomechanics
Volume 22Issue 9September 2022

History

Received: Mar 2, 2021
Accepted: Mar 7, 2022
Published online: Jul 7, 2022
Published in print: Sep 1, 2022
Discussion open until: Dec 7, 2022

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Associate Professor, School of Civil Engineering and Mechanics, Yanshan Univ., Qinhuangdao, Hebei 066004, China; Key Laboratory of Green Construction and Intelligent Maintenance for Civil Engineering of Hebei Province, Yanshan Univ., Qinhuangdao, Hebei 066004, China (corresponding author). Email: [email protected]
Master’s Student, School of Civil Engineering and Mechanics, Yanshan Univ., Qinhuangdao, Hebei 066004, China; Key Laboratory of Green Construction and Intelligent Maintenance for Civil Engineering of Hebei Province, Yanshan Univ., Qinhuangdao, Hebei 066004, China. ORCID: https://orcid.org/0000-0002-8047-3996. Email: [email protected]
Associate Professor, School of Civil Engineering and Mechanics, Yanshan Univ., Qinhuangdao, Hebei 066004, China; Key Laboratory of Green Construction and Intelligent Maintenance for Civil Engineering of Hebei Province, Yanshan Univ., Qinhuangdao, Hebei 066004, China. Email: [email protected]
Associate Professor, School of Civil Engineering and Mechanics, Yanshan Univ., Qinhuangdao, Hebei Province 066004, China; Key Laboratory of Green Construction and Intelligent Maintenance for Civil Engineering of Hebei Province, Yanshan Univ., Qinhuangdao, Hebei 066004, China. ORCID: https://orcid.org/0000-0002-7388-4404. Email: [email protected]

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Cited by

  • Limit Analysis for 3D Stability of Unsaturated Inhomogeneous Slopes Reinforced with Piles, International Journal of Geomechanics, 10.1061/IJGNAI.GMENG-7802, 23, 4, (2023).
  • Three-dimensional soil slope dynamic stability assessment using minimum potential energy approach, Soil Dynamics and Earthquake Engineering, 10.1016/j.soildyn.2023.107837, 168, (107837), (2023).

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