Technical Papers
Jul 27, 2022

A Semianalytical Model for Three-Dimensional Stability Analysis of Potentially Rotational Slopes in Unsaturated Soils

Publication: International Journal of Geomechanics
Volume 22, Issue 10

Abstract

Stability analysis of slopes subjected to steady infiltration is a hot topic in geotechnical engineering. However, the existing three-dimensional (3D) upper-bound limit analyses of unsaturated rotational slopes failed to take variable strength parameters and hydraulic parameters in space into account. To fill this gap, a semianalytical model is developed to capture the factor of safety (FS) and the critical failure region of unsaturated slopes based on the kinematical approach of limit analysis (KALA). A 3D rotational failure mechanism of unsaturated slopes subjected to steady vertical infiltrations is generated by a “point-by-point” technique, which can readily incorporate spatially variable strength parameters and hydraulic parameters. The work rates are calculated to formulate the objective function of FS, and the critical FS are optimized. The proposed model is validated through comparisons with the existing solutions and numerical solutions in terms of both the FSs and the failure patterns. The combined effects of hydraulic parameters and the size of slopes are investigated. An application to the stability analyses of unsaturated slopes with spatially variable physical parameters demonstrates that the proposed model has the potential to serve as a benchmark for the KALA of unsaturated slopes under complex geological conditions. Generally, the described framework can help geotechnical designers quickly evaluate the stability of unsaturated slopes in the preliminary design phase if the water table elevation is available and the hydraulic and strength parameters have been calibrated.

Get full access to this article

View all available purchase options and get full access to this article.

Acknowledgments

The authors have received financial support from the Innovation Foundation of Central South University (Grant No. 1053320192343), the National Key R&D Program of China (Grant No. 2017YFB1201204), the Systematic Project of Guangxi Key Laboratory of Disaster Prevention and Engineering Safety (Grant No. 2020ZDK010), and the Fundamental Research Funds for the Central Universities (Grant No. JUSRP121055).

Notation

The following symbols are used in this paper:
cap
apparent cohesion;
c
effective cohesion of soils;
ct
total cohesion;
COV(i) (i
ks, φ′, c′, 1/α, n) = variation coefficients of the mechanical and hydraulic parameters;
Gs
specific gravity of soils;
H
slope height;
ks
saturated hydraulic conductivity;
Ly: (Lz)
autocorrelation distances in the Y (Z) direction;
n
pore size distribution of soils;
q
specific discharge under vertical steady flow condition;
Ri,j
polar radius of the gravity centers of regular triangle Ti,j;
Ri,j
polar radius of the gravity centers of inverted triangle Ti,j;
S
water saturation degree;
Sr
residual degrees of saturation;
Se
effective degrees of saturation;
Si,j
area of regular triangle Ti,j;
Si,j
area of regular triangle Ti,j;
uw
pore water pressures;
Vi,j
volume of regular triangle Ti,j;
Vi,j
volume of regular triangle Ti,j;
vi,j
velocity magnitude of regular triangle Ti,j;
vi,j
velocity magnitude of inverted triangle Ti,j;
W
slope width;
W˙D
internal energy dissipation;
W˙γ
work rate done by soil weight;
W1
width of the initial cross section of the 3D discretized failure mechanism;
z
vertical distance between the water table and the specified point within slopes;
zu
vertical distance between the slope toe and the location of water table elevation;
α
inverse of the air entry pressure;
β
slope inclination;
δψ
discretization angle between two adjacent points on a radial plane of the 3D discretized failure mechanism;
δθ
discretization angle between two adjacent radial planes of the 3D discretized failure mechanism;
φ
effective friction angle of soils;
γsat
saturated unit weight of soils;
γw
water unit weight;
η
radial angle of the maximum cross section of the 3D discretized failure mechanism;
λi,j
length parameter of the discretized point Pi,j of the 3D discretized failure mechanism;
μi
(i = ks, φ′, c′, 1/α, n) means of the mechanical and hydraulic parameters;
ρi
(i = ks, φ′, c′, 1/α, n) autocorrelation coefficients of the mechanical and hydraulic parameters;
ρc,φln
cross-correlation coefficient of the effective soil cohesion and frictional angles;
ρ1/a,nln
cross-correlation coefficient of the pore size distribution coefficient of soils and the air entry pressure;
σ
total stresses of soils;
σ
effective stresses of soils;
σs
suction stress;
τ
shear stress;
ω
rotational angular velocity; and
ψi,j
angular parameter of the discretized point Pi,j of the 3D discretized failure mechanism.

References

Cavalcante, A. L. B., L. P. D. F. Borges, and J. G. Zornberg. 2019. “New 3D analytical solution for modeling transient unsaturated flow due to wetting and drying.” Int. J. Geomech. 19 (7): 04019077. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001461.
Chen, G. H., J. F. Zou, Q. J. Pan, Z. H. Qian, and H. Y. Shi. 2020. “Earthquake-induced slope displacements in heterogeneous soils with tensile strength cut-off.” Comput. Geotech. 124: 103637. https://doi.org/10.1016/j.compgeo.2020.103637.
Chen, Z., X. Wang, C. Haberfield, J. H. Yin, and Y. Wang. 2001. “A three-dimensional slope stability analysis method using the upper bound theorem Part I: Theory and methods.” Int. J. Rock Mech. Min. Sci. 38 (3): 369–378. https://doi.org/10.1016/S1365-1609(01)00012-0.
Cheng, Y. M., T. Lansivaara, and W. B. Wei. 2007. “Two-dimensional slope stability analysis by limit equilibrium and strength reduction methods.” Comput. Geotech. 34 (3): 137–150. https://doi.org/10.1016/j.compgeo.2006.10.011.
Cho, S. E. 2010. “Probabilistic assessment of slope stability that considers the spatial variability of soil properties.” J. Geotech. Geoenviron. Eng. 136 (7): 975–984. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000309.
Fávero Neto, A. H., A. Askarinejad, S. M. Springman, and R. I. Borja. 2020. “Simulation of debris flow on an instrumented test slope using an updated Lagrangian continuum particle method.” Acta Geotechnica. 15 (10): 2757–2777. https://doi.org/10.1007/s11440-020-00957-1.
Farzaneh, O., and F. Askari. 2003. “Three-dimensional analysis of nonhomogeneous slopes.” J. Geotech. Geoenviron. Eng. 129 (2): 137–145. https://doi.org/ 10.1061/(ASCE)1090-0241(2003)129:2(137).
Farzaneh, O., F. Askari, and N. Ganjian. 2008. “Three-dimensional stability analysis of convex slopes in plan view.” J. Geotech. Geoenviron. Eng. 134 (8): 1192–1200. https://doi.org/10.1061/(ASCE)1090-0241(2008)134:8(1192).
Fredlund, D. G., N. R. Morgenstern, and R. A. Widger. 1978. “The shear strength of unsaturated soils.” Can. Geotech. J. 15 (3): 313–321. https://doi.org/10.1139/t78-029.
Fredlund, D. G., A. Xing, M. D. Fredlund, and S. L. Barbour. 1996. “The relationship of the unsaturated soil shear strength to the soil-water characteristic curve.” Can. Geotech. J. 33 (3): 440–448. https://doi.org/10.1139/t96-065.
Gallipoli, D., S. J. Wheeler, and M. Karstunen. 2003a. “Modelling the variation of degree of saturation in a deformable unsaturated soil.” Géotechnique 53 (1): 105–112. https://doi.org/10.1680/geot.53.1.105.37249.
Gallipoli, D., A. Gens, R. Sharma, and J. Vaunat. 2003b. “An elasto-plastic model for unsaturated soil incorporating the effects of suction and degree of saturation on mechanical behaviour.” Géotechnique 53 (1): 123–135. https://doi.org/10.1680/geot.2003.53.1.123.
Gallipoli, D. 2012. “A hysteretic soil-water retention model accounting for cyclic variations of suction and void ratio. Geotechnique 62 (7): 605–616. https://doi.org/10.1680/geot.11.P.007.
Griffiths, D. V., and N. Lu. 2005. “Unsaturated slope stability analysis with steady infiltration or evaporation using elasto-plastic finite elements.” Int. J. Numer. Anal. Methods Geomech. 29 (3): 249–267. https://doi.org/10.1002/nag.413.
Haeri, S. M., A. Akbari Garakani, and M. Kamali Zarch. 2021. “Unsaturated 3D column method: New method for evaluation of stability of unsaturated slopes subjected to vertical steady-state infiltration and evaporation.” Int. J. Geomech. 21 (10): 04021177. https://doi.org/10.1061/(ASCE)GM.1943-5622.0002125.
Hungr, O. 1987. “An extension of Bishop’s simplified method of slope stability analysis to three dimensions.” Géotechnique 37 (1): 113–117. https://doi.org/10.1680/geot.1987.37.1.113.
Jiang, S. H., X. Liu, and J. Huang. 2022. “Non-intrusive reliability analysis of unsaturated embankment slopes accounting for spatial variabilities of soil hydraulic and shear strength parameters.” Eng. Comput. 38 (S1): 1–14. https://doi.org/10.1007/s00366-020-01108-6.
Kassim, A., N. Gofar, L. M. Lee, and H. Rahardjo. 2012. “Modeling of suction distributions in an unsaturated heterogeneous residual soil slope.” Eng. Geol. 131–132: 70–82. https://doi.org/10.1016/j.enggeo.2012.02.005.
Kim, J., S. Jeong, S. Park, and J. Sharma. 2004. “Influence of rainfall-induced wetting on the stability of slopes in weathered soils.” Eng. Geol. 75 (3–4): 251–262. https://doi.org/10.1016/J.ENGGEO.2004.06.017.
Le, T. M. H., D. Gallipoli, M. Sánchez, and S. Wheeler. 2015. “Stability and failure mass of unsaturated heterogeneous slopes.” Can. Geotech. J. 52 (11): 1747–1761. https://doi.org/10.1139/cgj-2014-0190.
Li, Y., J. Wu, and K. Li. 2012. “Saturated-unsaturated seepage analysis based on FLAC3D.” Rock Soil Mech. 33 (2): 617–622. https://doi.org/10.1061/(asce)gm.1943-5622.0001903.
Li, Z. W., and X. L. Yang. 2018. “Stability of 3D slope under steady unsaturated flow condition.” Eng. Geol. 242: 150–159. https://doi.org/10.1016/j.enggeo.2018.06.004.
Likos, W. J., N. Lu, and J. W. Godt. 2014. “Hysteresis and uncertainty in soil water-retention curve parameters.” J. Geotech. Geoenviron. Eng. 140 (4): 04013050. https://doi.org/10.1061/(ASCE)GT.1943-5606.0001071.
Lim, T. T., H. Rahardjo, M. F. Chang, and D. G. Fredlund. 1996. “Effect of rainfall on matric suctions in a residual soil slope.” Can. Geotech. J. 33 (4): 618–628. https://doi.org/10.1139/t96-087.
Lu, N., and J. Godt. 2008. “Infinite slope stability under steady unsaturated seepage conditions.” Water Resour. Res. 44 (11): W11404. https://doi.org/10.1029/2008WR006976.
Lu, N., and W. Likos. 2004. Unsaturated soil mechanics. Chichester, UK: Wiley.
Luo, F., G. Zhang, and C. Ma. 2021. “On the soil slope failure mechanism considering the mutual effect of bedrock and drawdown.” Int. J. Geomech. 21 (2): 04020247. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001903.
Mahmoodabadi, M., and L. S. Bryson. 2021a. “Prediction of coupled hydromechanical behavior of unsaturated soils based on seasonal variations in hydrologic conditions.” Can. Geotech. J. 58 (6): 902–913. https://doi.org/10.1139/cgj-2020-0388.
Mahmoodabadi, M., and L. S. Bryson. 2021b. “Constitutive model for describing the fully coupled hydromechanical behavior of unsaturated soils.” Int. J. Geomech. 21 (4): 04021027. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001975.
Michalowski, R. L., and A. Drescher. 2009. “Three-dimensional stability of slopes and excavations.” Géotechnique 59 (10): 839–850. https://doi.org/10.1680/geot.8.P.136.
Mollon, G., D. Dias, and A. H. Soubra. 2011. “Rotational failure mechanisms for the face stability analysis of tunnels driven by a pressurized shield.” Int. J. Numer. Anal. Methods Geomech. 35 (12): 1363–1388. https://doi.org/10.1002/nag.962.
Nam, S., M. Gutierrez, P. Diplas, J. Petrie, A. Wayllace, N. Lu, and J. J. Muñoz. 2010. “Comparison of testing techniques and models for establishing the SWCC of riverbank soils.” Eng. Geol. 110 (1–2): 1–10. https://doi.org/10.1016/j.enggeo.2009.09.003.
Nguyen, T. S., and S. Likitlersuang. 2019. “Reliability analysis of unsaturated soil slope stability under infiltration considering hydraulic and shear strength parameters.” Bull. Eng. Geol. Environ. 78 (8): 5727–5743. https://doi.org/10.1007/s10064-019-01513-2.
Pan, Q., J. Xu, and D. Dias. 2017. “Three-Dimensional stability of a slope subjected to seepage forces.” Int. J. Geomech. 17 (8): 4017035. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000913.
Pantelidis, L., E. Gravanis, and K. P. Gkotsis. 2020. “Stability assessment of soil slopes in three dimensions: The effect of the width of failure and of tension crack.” Geomech. Eng. 22 (4): 319–328.
Pantelidis, L., and D. V. Griffiths. 2013. “Stability of earth slopes. Part II: Three dimensional analysis in closed-form.” Int. J. Numer. Anal. Methods Geomech. 37 (13): 1987–2004. https://doi.org/10.1002/nag.2116.
Phoon, K. K., A. Santoso, and S. T. Quek. 2010. “Probabilistic analysis of soil-water characteristic curves.” J. Geotech. Geoenviron. Eng. 136 (3): 445–455. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000222.
Phoon, K. K., and J. Ching. 2015. Risk and reliability in geotechnical engineering. Boca Raton. FL: CRC Press.
Qi, S., D. Ling, Q. Yao, G. Lu, X. Yang, and J. W. Zhou. 2021. “Evaluating slope stability with 3D limit equilibrium technique and its application to landfill in China.” Eng. Geol. 280: 105939. https://doi.org/10.1016/j.enggeo.2020.105939.
Qian, Z. H., X. X. Wei, Q. Huang, and J. F. Zou. 2022. “Earth pressure estimation of undrained soil–wall systems with head rotation.” Int. J. Geomech. 22 (6): 04022081. https://doi.org/10.1061/(ASCE)GM.1943-5622.0002380.
Qian, Z. H., J. F. Zou, and Q. J. Pan. 2021. “3D discretized rotational failure mechanism for slope stability analysis.” Int. J. Geomech. 21 (11): 04021210. https://doi.org/10.1061/(ASCE)GM.1943-5622.0002163.
Qian, Z. H., J. F. Zou, Q. J. Pan, G. H. Chen, and S. X. Liu. 2020. “Discretization-based kinematical analysis of three-dimensional seismic active earth pressures under nonlinear failure criterion.” Comput. Geotech. 126: 103739. https://doi.org/10.1016/j.compgeo.2020.103739.
Qin, C., and S. C. Chian. 2018. “Bearing capacity analysis of a saturated non-uniform soil slope with discretization-based kinematic analysis.” Comput. Geotech. 96: 246–257. https://doi.org/10.1016/j.compgeo.2017.11.003.
Rojas, E., J. Horta, T. López-Lara, and J. B. Hernández. 2020. “Simulating undrained tests on unsaturated soils.” Int. J. Geomech. 20 (2): 04019165. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001558.
Sivakumar, V. 1993. “A critical state framework for unsaturated soil.” Doctoral dissertation, Univ. of Sheffield.
Sun, D., L. Wang, and L. Li. 2019. “Stability of unsaturated soil slopes with cracks under steady-infiltration conditions.” Int. J. Geomech. 19 (6): 04019044. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001398.
Tan, X., P. Li, M. Shen, M. Hu, X. Hou, and H. Ma. 2020. “Evaluation of the spatial variability characteristics of the unsaturated clay in Hefei, China.” Soils Found. 60 (2): 454–465. https://doi.org/10.1016/j.sandf.2020.03.010.
Tang, M. G., Q. Xu, R. Q. Huang, and G. Q. Qi. 2006. “Experiment and analysis of suction of unsaturated soil in slope.” Chin. J. Rock Mech. Eng. 25 (2): 355–362.
Vahedifard, F., D. Leshchinsky, K. Mortezaei, and N. Lu. 2016. “Effective stress-based limit-equilibrium analysis for homogeneous unsaturated slopes.” Int. J. Geomech. 16 (6): D4016003. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000554.
Wang, L., W. Hu, D. Sun, and L. Li. 2019a. “3D stability of unsaturated soil slopes with tension cracks under steady infiltrations.” Int. J. Numer. Anal. Methods Geomech. 43 (6): 1184–1206. https://doi.org/10.1002/nag.2889.
Wang, L., D. Sun, B. Chen, and J. Li. 2019b. “Three-dimensional seismic stability of unsaturated soil slopes using a semianalytical method.” Comput. Geotech. 110: 296–307. https://doi.org/10.1016/j.compgeo.2019.02.008.
Wang, L., D. Sun, and L. Li. 2019c. “3D stability of partially saturated soil slopes after rapid drawdown by a new layer-wise summation method.” Landslides 16 (2): 295–313. https://doi.org/10.1007/s10346-018-1081-2.
Xu, J. S., and X. L. Yang. 2018. “Three-dimensional stability analysis of slope in unsaturated soils considering strength nonlinearity under water drawdown.” Eng. Geol. 237: 102–115. https://doi.org/10.1016/j.enggeo.2018.02.010.
Yang, H. Q., L. Zhang, J. Xue, J. Zhang, and X. Li. 2019. “Unsaturated soil slope characterization with Karhunen–Loève and polynomial chaos via Bayesian approach.” Eng. Comput. 35 (1): 337–350. https://doi.org/10.1007/s00366-018-0610-x.
Yang, X. L., and Z. W. Li. 2018. “Comparison of factors of safety using a 3D failure mechanism with kinematic approach.” Int. J. Geomech. 18 (9): 04018107. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001235.
Zhu, D. Y., C. F. Lee, and H. D. Jiang. 2003. “Generalised framework of limit equilibrium methods for slope stability analysis.” Géotechnique 53 (4): 377–395. https://doi.org/10.1680/geot.2003.53.4.377.

Information & Authors

Information

Published In

Go to International Journal of Geomechanics
International Journal of Geomechanics
Volume 22Issue 10October 2022

History

Received: Nov 8, 2021
Accepted: May 8, 2022
Published online: Jul 27, 2022
Published in print: Oct 1, 2022
Discussion open until: Dec 27, 2022

Permissions

Request permissions for this article.

ASCE Technical Topics:

Authors

Affiliations

School of Civil Engineering, Central South Univ., No.22, Shaoshan South Rd., Changsha 410075, China (corresponding author). ORCID: https://orcid.org/0000-0002-5333-0113. Email: [email protected]
School of Environment and Civil Engineering, Jiangnan Univ., No. 1800 Lihu Ave., Wuxi 214122, China. Email: [email protected]
Dept. of Civil Engineering, Shanghai Univ., No. 99, Shangda Rd., Shanghai 200444, China. Email: [email protected]
Jin-Feng Zou [email protected]
School of Civil Engineering, Central South Univ., No.22, Shaoshan South Rd., Changsha 410075, China. Email: [email protected]

Metrics & Citations

Metrics

Citations

Download citation

If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.

Cited by

  • Three-dimensional blow-out stability analysis of shield tunnel face in anisotropic and heterogeneous soils, Tunnelling and Underground Space Technology, 10.1016/j.tust.2022.104851, 131, (104851), (2023).

View Options

Get Access

Access content

Please select your options to get access

Log in/Register Log in via your institution (Shibboleth)
ASCE Members: Please log in to see member pricing

Purchase

Save for later Information on ASCE Library Cards
ASCE Library Cards let you download journal articles, proceedings papers, and available book chapters across the entire ASCE Library platform. ASCE Library Cards remain active for 24 months or until all downloads are used. Note: This content will be debited as one download at time of checkout.

Terms of Use: ASCE Library Cards are for individual, personal use only. Reselling, republishing, or forwarding the materials to libraries or reading rooms is prohibited.
ASCE Library Card (5 downloads)
$105.00
Add to cart
ASCE Library Card (20 downloads)
$280.00
Add to cart
Buy Single Article
$35.00
Add to cart

Get Access

Access content

Please select your options to get access

Log in/Register Log in via your institution (Shibboleth)
ASCE Members: Please log in to see member pricing

Purchase

Save for later Information on ASCE Library Cards
ASCE Library Cards let you download journal articles, proceedings papers, and available book chapters across the entire ASCE Library platform. ASCE Library Cards remain active for 24 months or until all downloads are used. Note: This content will be debited as one download at time of checkout.

Terms of Use: ASCE Library Cards are for individual, personal use only. Reselling, republishing, or forwarding the materials to libraries or reading rooms is prohibited.
ASCE Library Card (5 downloads)
$105.00
Add to cart
ASCE Library Card (20 downloads)
$280.00
Add to cart
Buy Single Article
$35.00
Add to cart

Media

Figures

Other

Tables

Share

Share

Copy the content Link

Share with email

Email a colleague

Share