Effect of a less permeable stronger soil layer on the stability of non-homogeneous unsaturated slopes

Abstract

Slope failure occurs due to an increase in the saturation level and a subsequent decrease in matric suction in unsaturated soil. This paper presents the results of a series of centrifuge experiments and numerical analyses on a 55° inclined unsaturated sandy slope with less permeable, stronger silty sand layer inclusion within it. It is observed that a less permeable, stronger silty sand layer in an otherwise homogeneous sandy soil slope hinders the infiltration of water. The water content of the slope just above the stronger layer increases significantly, compared to elsewhere. No shear band is found to initiate in a homogeneous sandy soil slope, whereas for a non-homogeneous slope, they initiate just above the less pervious, stronger layer. A discontinuity of the shear zone is also observed for the case of a non-homogeneous soil slope. The factor of safety of a non-homogeneous, unsaturated soil slope decreases because of the less permeable, stronger layer. It decreases significantly if this less permeable, stronger soil layer is located near the toe of the slope.

Keywords

non-homogeneous slope / stronger soil layer / factor of safety / centrifuge model test / unsaturated soils

References

[1] Brown W M, Sitar N, Saarinen T F, Blair M L. Overview and summary of debris flows, landslides, and floods in the San Francisco Bay region, January 1982. In: Conference on Debris Flows, Landslides, and Floods in the San Francisco Bay region. Stanford, CA: Stanford University, 1982

[2] Lagmay A M F, Ong J B T, Fernandez D F D, Lapus M R, Rodolfo R S, Tengonciang A M P, Soria J L A, Baliatan E G, Quimba Z L, Uichanco E, Paguican A. Scientists investigate recent Philippine landslide. American Geophysical Union, 2006, 87(12): 121–128

[3] Dey N, Sengupta A. Effect of rainfall on the triggering of the devastating slope failure at Malin, India. Natural Hazards, 2018, 94(3): 1391–1413

[4] Schuster R L, Salcedo D A, Valenzuela L. Overview of catastrophic landslides of South America in the twentieth century. Reviews in Engineering Geology, 2002, 15: 1–34

[5] Van Sint Jan M, Talloni P. Sediment flow 18 June 1991 in Antofagasta: La Serena, Chile. In: The Third Chilean Congress of Geotechnical Engineering. 1993, 1: 247–265

[6] Borja R, White J, Liu X, Wu W. Factor of safety in a partially saturated slope inferred from hydro-mechanical continuum modeling. International Journal for Numerical and Analytical Methods in Geomechanics, 2012, 36(2): 236–248

[7] Wang D, Wang J, Wu J, Deng J, Sun M. A three-dimensional two-level gradient smoothing meshfree method for rainfall induced landslide simulations. Frontiers of Structural and Civil Engineering, 2019, 13(2): 337–352

[8] Fredlund D G, Morgenstern N R, Widger R A. The shear strength of unsaturated soils. Canadian Geotechnical Journal, 1978, 15(3): 313–321

[9] Lu N, Wayllace A, Oh S. Infiltration-induced seasonally reactivated instability of a highway embankment near the Eisenhower Tunnel, Colorado, USA. Engineering Geology, 2013, 162: 22–32

[10] Vanapalli S K, Fredlund D G, Pufahl D E, Clifton A W. Model for the prediction of shear strength with respect to soil suction. Canadian Geotechnical Journal, 1996, 33(3): 379–392

[11] Zhan L. Soil-water interaction in unsaturated expansive soil slopes. Frontiers of Structural and Civil Engineering, 2007, 1(2): 198–204

[12] Wilson C J, Dietrich W E. The contribution of bedrock groundwater flow to storm runoff and high pore pressure development in hollows. IAHS-AISH Publication, 1987, 165: 49–59

[13] Wu J J, Li Y, Cheng Q G, Wen H, Liang X. A simplified method for the determination of vertically loaded pile-soil interface parameters in layered soil based on FLAC 3D. Frontiers of Structural and Civil Engineering, 2016, 10(1): 103–111

[14] Wu L Z, Huang R Q, Li H L, Li X, Sun P. The model tests of rainfall infiltration in two-layer unsaturated soil slopes. European Journal of Environmental and Civil Engineering, 2019, 23: 1–15

[15] Chatterjee D, Murali Krishna A. Stability analysis of two-layered non-homogeneous slopes. International Journal of Geotechnical Engineering, 2018, 3: 1–7

[16] Goh A T. Genetic algorithm search for critical slip surface in multiple-wedge stability analysis. Canadian Geotechnical Journal, 1999, 36(2): 382–391

[17] Ho I H. Numerical study of slope-stabilizing piles in undrained clayey slopes with a weak thin layer. International Journal of Geomechanics, 2015, 15(5): 06014025

[18] Al-Homoud A S, Tubeileh T K. Analysis and remedies of landslides of cut slopes due to the presence of weak cohesive layers within stronger formations. Environmental Geology, 1998, 33(4): 299–311

[19] Wang R, Zhang G, Zhang J M. Centrifuge modelling of clay slope with montmorillonite weak layer under rainfall conditions. Applied Clay Science, 2010, 50(3): 386–394

[20] GeoStudio. Tutorial Manual. GEO-SLOPE International Ltd, 2007

[21] Dell’Avanzi E, Zornberg J G, Cabral A R. Suction profiles and scale factors for unsaturated flow under increased gravitational field. Soil and Foundation, 2004, 44(3): 79–89

[22] Taylor R N. Geotechnical Centrifuge Technology. London: Taylor and Francis, 1995

[23] Ng C W W, Kamchoom V, Leung A K. Centrifuge modelling of the effects of root geometry on transpiration-induced suction and stability of vegetated slopes. Landslides, 2015, 13(5): 1–14

[24] Raj M, Sengupta A. Rain-triggered slope failure of the railway embankment at Malda, India. ActaGeotechnica, 2014, 9(5): 789–798

[25] Zhang M, Zhang J, Lai Y. Numerical analysis for critical height of railway embankment in permafrost regions of Qinghai-Tibetan plateau. Cold Regions Science and Technology, 2005, 41(2): 111–120

[26] White D J, Take W A. Geo-PIV: Particle Image Velocimetry (PIV) Software for Use in Geotechnical Testing. Technical Report. Cambridge: University of Cambridge, 2002

[27] Lu N, Likos W J. Suction stress characteristic curve for unsaturated soil. Journal of Geotechnical and Geoenvironmental Engineering, 2006, 132(2): 131–142

[28] Childs E C, Collis-George N. The permeability of porous materials. Proceedings of the Royal Society, 1950, 201(1066): 392–405

[29] Richards L A. Capillary conduction of liquids through porous mediums. Journal of Applied Physics, 1931, 1(5): 318–333

[30] van Genuchten M T. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Science Society of America Journal, 1980, 44(5): 892–898

[31] Fredlund D G, Xing A. Equations for the soil-water characteristic curve. Canadian Geotechnical Journal, 1994, 31(4): 521–532

[32] Bishop A W. The use of the slip circle in the stability analysis of slopes. Geotechnique, 1955, 5(1): 7–17

[33] Janbu N. Application of composite slip surfaces for stability analysis. In: Proceedings of European Conference on Stability of Earth Slopes. Stockholm, 1954, 3, 43–49

[34] Anitescu C, Atroshchenko E, Alajlan N, Rabczuk T. Artificial neural network methods for the solution of second order boundary value problems. Computers, Materials & Continua, 2019, 59(1): 345–359

[35] Guo H, Zhuang X, Rabczuk T. A deep collocation method for the bending analysis of Kirchhoff plate. Computers, Materials & Continua, 2019, 59(2): 433–456

[36] Rabczuk T, Ren H, Zhuang X. A nonlocal operator method for partial differential equations with application to electromagnetic waveguide problem. Computers, Materials & Continua, 2019, 59(1): 31–55

[37] Zhou S, Zhuang X, Rabczuk T. Phase-field modeling of fluid-driven dynamic cracking in porous media. Computer Methods in Applied Mechanics and Engineering, 2019, 350: 169–198

[38] Zhou S, Zhuang X, Rabczuk T. Phase field modeling of brittle compressive-shear fractures in rock-like materials: A new driving force and a hybrid formulation. Computer Methods in Applied Mechanics and Engineering, 2019, 355: 729–752

[39] Zhou S, Rabczuk T, Zhuang X. Phase field modeling of quasi-static and dynamic crack propagation: COMSOL implementation and case studies. Advances in Engineering Software, 2018, 122: 31–49

[40] Zhou S, Zhuang X, Rabczuk T. A phase-field modeling approach of fracture propagation in poroelastic media. Engineering Geology, 2018, 240: 189–203

[41] Zhou S, Zhuang X, Zhu H, Rabczuk T. Phase field modelling of crack propagation, branching and coalescence in rocks. Theoretical and Applied Fracture Mechanics, 2018, 96: 174–192

Acknowledgement

The centrifuge tests reported here were funded by the HYDRODRIL project sponsored by the European Commission (FP7-PEOPLE-2011-IRES-Proposal No. 295225). The authors acknowledge the permissions and help received during these tests from Prof. Wei Wu, of the Institute of Geotechnical Engineering, Universität für Bodenkultur (BOKU), Vienna, Austria.

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