Assessment of rainfall-induced slope failures is important in reducing damage to infrastructures as well as guarantee safety of people living close to hazardous areas. This study presents case studies and numerical investigations of three unstable unsaturated slopes. The studied slopes are two natural slopes (Slopes T16 and T2) along the Taipei Maokong Gondola (Cable Transit) system and one unstable 26 m high multi-tier geosynthetic-reinforced soil (GRS) slope with marginal backfill in Taichung County, Taiwan.
Slope T16 collapsed during torrential rainfall during Typhoon Jangmi in September 2008, and another nearby slope (T2) developed excessive deformation under consecutive wetting and drying cycles. The GRS slope first experienced excessive deformation after seasons of typhoon and heavy rainfall from 2010-2012. The measured settlement and horizontal deflection at slope crest were 140 and 80 cm respectively from June to December 2012. Although an immediate remediation had been conducted for the slope excessive deformation, the slope final collapse was caused by two sequential typhoon events with total accumulated rainfall over 600 mm in August 2013.
Recorded rainfall, measured soil parameters, site geology, and slope geometry were used in coupled hydro-mechanical finite element analyses to investigate the failure and deformation mechanisms of these three slopes. The numerical results demonstrated that the coupled hydro-mechanical analysis based on the framework of unsaturated soil mechanics satisfactorily predicted deformation characteristics and failure timing of unsaturated soil slopes during rainfall. The slopes’ failure was attributed to a decrease in soil shear strength when the matric suction gradually decreased as rainfall progressed.
Examination of the relationships between the slope factor of safety and the corresponding hydrological data (i.e., rainfall and soil PWP) revealed that coupled hydro-mechanical analysis combined with detailed site investigation could be performed to establish factor of safety (FS) versus accumulated rainfall relationship for slopes to act as reference in disaster mitigation (forecasting) strategies. Findings of this study implies that continuous assessment of slope stability during wetting and drying cycles is significant in order to circumvent catastrophic slope failures. In addition, it is crucial to pay special attention to unstable rock or soil layers (such as weathered sandstone interbedded with shale layers) prior to design or construction of the GRS slope as well as to drainage installations to ensure that they remain intact and efficient if slope deforms. Lessons learned from this study are discussed, and remedial measures to improve the slope stability are proposed and evaluated. The significance of this study is to provide means for assessing and predicting slope stability (deformation and failure timing) using recorded rainfall, measured soil parameters, site geology, and slope geometry in order to mitigate the catastrophic damage and failure caused by natural and reinforced slopes failure during heavy rainfall.

Assessment of rainfall-induced slope failures is important in reducing damage to infrastructures as well as guarantee safety of people living close to hazardous areas. This study presents case studies and numerical investigations of three unstable unsaturated slopes. The studied slopes are two natural slopes (Slopes T16 and T2) along the Taipei Maokong Gondola (Cable Transit) system and one unstable 26 m high multi-tier geosynthetic-reinforced soil (GRS) slope with marginal backfill in Taichung County, Taiwan.
Slope T16 collapsed during torrential rainfall during Typhoon Jangmi in September 2008, and another nearby slope (T2) developed excessive deformation under consecutive wetting and drying cycles. The GRS slope first experienced excessive deformation after seasons of typhoon and heavy rainfall from 2010-2012. The measured settlement and horizontal deflection at slope crest were 140 and 80 cm respectively from June to December 2012. Although an immediate remediation had been conducted for the slope excessive deformation, the slope final collapse was caused by two sequential typhoon events with total accumulated rainfall over 600 mm in August 2013.
Recorded rainfall, measured soil parameters, site geology, and slope geometry were used in coupled hydro-mechanical finite element analyses to investigate the failure and deformation mechanisms of these three slopes. The numerical results demonstrated that the coupled hydro-mechanical analysis based on the framework of unsaturated soil mechanics satisfactorily predicted deformation characteristics and failure timing of unsaturated soil slopes during rainfall. The slopes’ failure was attributed to a decrease in soil shear strength when the matric suction gradually decreased as rainfall progressed.
Examination of the relationships between the slope factor of safety and the corresponding hydrological data (i.e., rainfall and soil PWP) revealed that coupled hydro-mechanical analysis combined with detailed site investigation could be performed to establish factor of safety (FS) versus accumulated rainfall relationship for slopes to act as reference in disaster mitigation (forecasting) strategies. Findings of this study implies that continuous assessment of slope stability during wetting and drying cycles is significant in order to circumvent catastrophic slope failures. In addition, it is crucial to pay special attention to unstable rock or soil layers (such as weathered sandstone interbedded with shale layers) prior to design or construction of the GRS slope as well as to drainage installations to ensure that they remain intact and efficient if slope deforms. Lessons learned from this study are discussed, and remedial measures to improve the slope stability are proposed and evaluated. The significance of this study is to provide means for assessing and predicting slope stability (deformation and failure timing) using recorded rainfall, measured soil parameters, site geology, and slope geometry in order to mitigate the catastrophic damage and failure caused by natural and reinforced slopes failure during heavy rainfall.

AASHTO (2002). "Standard Specifications for Highway Bridges." , American Association of State Highway and Transportation Officials, Washington, D.C., with interims.
Abed, A. (2008). "Numerical Modeling of Expansive Soil Behavior." Ph. D disertation, , Universität Stuttgart, Germany.
Alonso, E. E. (2006). "Field application of unsaturated soil mechanics." Advances in Unsaturated Soil, Seepage, and Environmental Geotechnics, ASCE, 1-33.
Alonso, E. E., Gens, A., and Delahaye, C. H. (2003). "Influence of rainfall on the deformation and stability of a slope in overconsolidated clays: a case study." Hydrogeology Journal, 11(1), 174-192.
Alonso, E.E., Gens, A. and Josa, A. (1990). "A constitutive model for partially saturated soils." Geotechnique, 40, 405-430
Amadi, A. A. (2014). "Enhancing durability of quarry fines modified black cotton soil subgrade with cement kiln dust stabilization." Transportation Geotechnics, 1(1), 55-61.
ASTM D2487 " Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort (12 400 ft-lbf/ft3 (600 kN-m/m3))" ASTM International, West Conshohocken, PA,USA.
ASTM D2487 "Standard practice for classification of soils for engineering purposes (Unified Soil Classification System)." ASTM International, West Conshohocken, PA,USA.
ASTM D2850 "Standard test method for unconsolidated-undrained triaxial compression test on cohesive soils." ASTM International, West Conshohocken, PA, USA.
ASTM D4318 "Standard test methods for liquid limit, plastic limit, and plasticity index of soils." ASTM International, West Conshohocken,PA,USA.
ASTM D4767 "Standard test method for consolidated undrained triaxial compression test for cohesive soils." ASTM International, West Conshohocken, PA,USA.
ASTM D5084 "Standard test methods for measurement of hydraulic conductivity of saturated porous materials using a flexible wall permeameter." ASTM International, West Conshohocken, PA,USA.
ASTM D6637/D6637M "Standard test method for determining tensile properties of geogrids by the single or multi-rib tensile method." ASTM International, West Conshohocken, PA,USA.
ASTM D6836-16 "Standard test methods for determination of the soil water characteristic curve for desorption using hanging column, pressure extractor, chilled mirror hygrometer, or centrifuge." ASTM International, West Conshohocken, PA,USA.
ASTM D6913 "Standard test methods for particle-size distribution (gradation) of soils using sieve analysis." ASTM International, West Conshohocken, PA,USA.
ASTM D7928 "Standard test method for particle-size distribution (gradation) of fine-grained soils using the sedimentation (hydrometer) analysis." ASTM International, West Conshohocken, PA,USA.
Azam, S., Ito, M., and Khan, F. (2013). "Influence of cracks on soil water characteristic curve." Advances in Unsaturated Soils C. e. a. (eds), ed., Taylor & Francis Group, London.
Baeza, C., and Corominas, J. (2001). "Assessment of shallow landslide susceptibility by means of multivariate statistical techniques." Earth Surface Processes and Landforms, 26(12), 1251-1263.
Benson, C. H., Gunter, J. A., Boutwell, G. P., Trautwein, S. J., and Berzanskis, P. H. (1997). "Comparison of four methods to asses hydraulic conductivity " Journal of Geotechnical and Geoenvironmental Engineering, 123(10), 929-937.
Blake, J. R., Renaud, J. P., Anderson, M. G., and Hencher, S. R. (2003). "Prediction of rainfall-induced transient water pressure head behind a retaining wall using a high-resolution finite element model." Computers and Geotechnics, 30(6), 431-442.
Bolton, M. D. (1986). "The strength and dilatancy of sands." Geotechnique 36, , 36(1), 65-78.
Borja, R. I., White, J. A., Liu, X., and Wu, W. (2012). "Factor of safety in a partially saturated slope inferred from hydro-mechanical continuum modeling." International Journal for Numerical and Analytical Methods in Geomechanics, 36(2), 236-248.
Bragg, W.H. (1913) "The Reflection of X-rays by Crystals (ΙΙ)." Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, 89, 246-247.
Brand E.W., Premchitt J. & Phillipson H.B. (1984) “Relationships between rainfall and landslides in Hong Kong.” Proceedings of IVth. Symposium on Landslides, Toronto, 1, 377-384.
Brinkgreve, R. B. J., Kumarswamy, S., and Swolfs, W. M. (2016). "PLAXIS 2016 Manual", Balkema, Rotterdam, The Netherlands.
Brooks, R. H., and Corey, A. T. (1964). "Hydraulic properties of porous media." Colorado State Universty, 1-37.
Cai F, Ugai K . 2004. Numerical analysis of rainfall effects on slope stability. International Journal of Geomechanics, 4(2), 69–78
Casini, F. (2013). "Coupled processes during rainfall- an experimental investigation on a silty sand." Poromechanics V, ASCE, 1542-1549.
Cascini, L., Cuomo, S., Pastor, M., and Sorbino, G. (2010). "Modeling of Rainfall-Induced Shallow Landslides of the Flow-Type." Journal of Geotechnical and Geoenvironmental Engineering, 136(1), 85-98.
Chae, B.-G., Lee, J.-H., Park, H.-J., and Choi, J. 2015. A method for predicting the factor of safety of an infinite slope based on the depth ratio of the wetting front induced by rainfall infiltration. Natural Hazards Earth System Science, 15, 1835-1849
Che, A.-l., Wu, Z.-j., and Wang, P. (2014). "Stability of pile foundations base on warming effects on the permafrost under earthquake motions." Soils and Foundations, 54(4), 639-647.
Chen, H. X., Zhang, L. M., Gao, L., Zhu, H., and Zhang, S. (2015). "Presenting regional shallow landslide movement on three-dimensional digital terrain." Engineering Geology, 195, 122-134.
Chen, J. F., Yeh, H. F., Lee, C. H., and Lo, W. C. (2005). "Optimal comparison of empirical equations for estimating potential evapotranspiration in Taiwan." XXXI IAHR CONGRESSSeoul, Korea, 3687-3697.
Chen, R. H., Chen, H. P., Chen, K. S., and Zhung, H. B. (2009). "Simulation of a slope failure induced by rainfall infiltration." Environmental Geology, 58(5), 943-952.
Cheng, YM, Lansivaara T, Wei WB. (2007). Two-dimensional slope stability analysis by limit quilibrium and strength reduction methods. Computers and Geotechnics, 34(3), 137–50
Chittoori, B., and Puppala, A. J. (2011). "Quantitative estimation of clay mineralogy in fine-grained soils." Journal of Geotechnical and Geoenvironmental Engineering, 137(11), 997-1008.
Cho, S. E. (2014). "Probabilistic stability analysis of rainfall-induced landslides considering spatial variability of permeability." Engineering Geology, 171, 11-20.
Cho, S. E., and Lee, S. R. (2001). "Instability of unsaturated soil slopes due to infiltration." Computer and Geotechnics, 28(3), 185-208.
Cho, S. E., and Lee, S. R. (2002). "Evaluation of surficial stability for homogeneous slopes considering rainfall characteristics." Journal of Geotechnical and Geoenvironmental Engineering,, 128(9), 756-763.
Collins, B. D., and Znidarcic, D. (2004). "Stability analyses of rainfall induced landslides." Journal of Geotechnical and Geoenvironmental Engineering,, 130(4), 362-372.
Cornforth, D. H. (2005). "Landslides in Practice - Investigation, Analysis, and Remedial/Preventative Options in Soils." John Wiley & Sons
Correia, N. S., and Zornberg, J. G. (2014). "Influence of tack coat rate on the properties of paving geosynthetics." Transportation Geotechnics, 1(1), 45-54.
Crozier M. (1986) “Climatic Triggering of Landslide Episodes. Landslides: Causes, Consequences And Environment”. Croom Helm
Cui, Y.-J., Lamas-Lopez, F., Trinh, V. N., Calon, N., D’Aguiar, S. C., Dupla, J.-C., Tang, A. M., Canou, J., and Robinet, A. (2014). "Investigation of interlayer soil behaviour by field monitoring." Transportation Geotechnics, 1(3), 91-105.
De Silva, L. I. N., Koseki, J., Wahyudi, S., and Sato, T. (2014). "Stress–dilatancy relationships of sand in the simulation of volumetric behavior during cyclic torsional shear loadings." Soils and Foundations, 54(4), 845-858.
Deere, D. U., and Deere, D. W. (1988). "The rock quality designation (RQD) index in practice." Rock Classifications Systems for Engineering Purposes, ASTM STP 984, America Society of Testing and Materials, , Philadelphia, , 91-101.
Duncan, J. M., and Wright S. G. (2005). "Soil strength and slope stabiliy." John Wiley & Sons
Bruker Corporation (2008). DIFFRACplus EVA, http://www.bruker-axs.com/eva.html.
Ehlers, W., Graf, T., and Ammann, M. (2004). "Deformation and localization analysis of partially saturated soil." Computer Methods in Applied Mechanics and Engineering, 193(27-29), 2885-2910.
Eichenberger, J., Nuth, M., and Laloui, L. (2011). "Modeling the onset of shallow landslides in partially saturated slopes." Geo-Frontiers 2011, ASCE, 1672-1682.
Elias, V., Christopher, B.R., and and Berg, R. (2001). " Mechanically stabilized earth walls and reinforced soil slopes design and construction guidelines. Report No. FHWA-NHI-00-043, National Highway Institute, Federal Highway Administration, Washington, D.C. March 2001."
Fan, C.-C. and Heish, C.-C. (2007). "A hybrid embankment system used in repairing collapsed roadway in mountainous area. "Proceedings of 16th Southeast Asia Geotechnical Conference, Kuala Lumpur, Malaysia, 8-11.
Fan, C.-C. and Hsiao C.-F. (2011). "Field performance of a hybrid reinforced earth embankment built adjacent to a slope with narrow fill space " Journal of GeoEngineering, 6 (1), 47-62
Fredlund, D. G. (2006). "Unsaturated soil mechanics in engineering practice." Journal of Geotechnical and Geoenvironmental Engineering, 132(3), 286-321.
Fredlund, D. G., and Morgenstern, N. R. (1977). "Stress-state variables for unsaturated soils." Proceedings of ASCE 103(No. GT5).
Fredlund, D. G., and Rahardjo, H. (1993). "Soil mechanics for unsaturated soils.", John Wiley and Sons, New York, USA.
Fredlund, D. G., and Xing, A. Q. (1994). "Equations for the soil water characteristic curve." Canadian Geotechnical Journal, 31, 521-532.
Fredlund, D. G., Xing, A. Q., and Juang, S. (1994). "Prediction the permeability functions for unsaturated soils using the soil-water characteristics curve." Canadian Geotechnical Journal, 31(4), 533-546.
Fredlund, D. G., Xing, A. Q., Fredlund, M. D., and Barbour, S. L. (1996). "The relationship of the unsaturated soil shear strength to the soil-water characteristic curve." Canadian Geotechnical Journal, 33(3), 440-448.
Fuselier, T., Edgers, L., and Nadim, F. 2006. "Transient flow in unsaturated soils: numerical analysis and case study." Unsaturated Soils 2006: pp. 2051-2062. doi: 10.1061/40802(189)173
Gan, J. K. M., Fredlund, D. G., and Rahardjo, H. (1988). "Determination of the shear strength parameters of an unsaturated soil using the direct shear test." canadian Geotechnical Journal, 25, 500-510.
Gens, A., Sa´nchez, M., and Sheng, D. (2006). "On constitutive modelling of unsaturated soils." Acta Geotechnica 1, 137–147.
Gerscovich, D. M. S., Vargas, E. A., and de Campos, T. M. P. (2006). "On the evaluation of unsaturated flow in a natural slope in Rio de Janeiro, Brazil." Engineering Geology, 88(1-2), 23-40.
Ghiabi, H., and Selvadurai, A. (2009). "Time-dependent mechanical behavior of a granular medium used in laboratory investigations." International Journal of Geomechanics, 9(1), 1-8.
Giraldo, J., and Rayhani, M. T. (2014). "Load transfer of hollow fiber-reinforced polymer (FRP) piles in soft clay." Transportation Geotechnics, 1(2), 63-73.
Gomes Correia, A., Tutumluer, E., and Chen, Y. (2014). "Editorial." Transportation Geotechnics, 1(1), 1-2. DOI: 10.1016/j.trgeo.2014.03.001
Goodman, R. E. (1989). "Introduction to Rock Mechanics", John Wiley and Sons.
Gribb, M. M., Kodesova, R., and Ordway, S. E. (2004). "Comparison of soil hydraulic property measurement methods." Journal of Geotechnical and Geoenvironmental Engineering, 130(10), 1084–1095.
Han, Z., and Vanapalli, S. K. (2015). "Model for predicting resilient modulus of unsaturated subgrade soil using soil-water characteristic curve." Canadian Geotechnical Journal, 1-15.
Hayashi, M. and Quinton, W. L. (2004). "A constant-head well permeameter method for measuring field-saturated hydraulic conductivity above an impermeable layer." Canadian Journal of Soil Science. 84 (3), 255–264
Hedayati, M., and Hossain, S. (2015). "Data based model to estimate subgrade moisture variation case study: Low volume pavement in North Texas." Transportation Geotechnics, 3, 48-57.
Hiff J. W. (1956). "An invenvestigation of pore water pressure in compacted cohesive soils." Ph. D Thesis. Technical Memorandum No. 654, United States Department of Interior Bureau of Reclamation, Design and Construction Division, Denver, Colarado, USA
Hoyos, L. R., Perez-Ruiz, D. D., and Puppala, A. J. (2012). "Refined true triaxial apparatus for testing unsaturated soils under suction-controlled stress paths." International Journal of Geomechanics, 12(3), 281-291.
Hsu, K.-C., Wang, C.-H., Chen, K.-C., Chen, C.-T., and Ma, K.-W. (2006). "Climate-induced hydrological impacts on the groundwater system of the Pingtung Plain, Taiwan." Hydrogeology Journal, 15(5), 903-913.
Huang C.-C., , Ju, Y.-J., Hwu, L.-K., and Lee J.-L. (2009). "Internal soil moisture and piezometric responses to rainfall-induced shallow slope failures." Journal of Hydrology, 370(1-4), 39-51.
Huang, C.-C., and Lo, C.-L. (2013). "Simulation of subsurface flows associated with rainfall-induced shallow slope failures. " Journal of GeoEngineering, 8(3), 101-111.
Iryo, T., and Rowe, R. K. (2003). "On the hydraulic behavior of unsaturate nonwoven geotextiles." Geotextiles and Geomembranes, 21, 381-404.
Iryo, T., and Rowe, R. K. (2004). "Numerical study of infiltration into a soil-geotextile column." Geosynthetics International, 11(5), 377-389.
Iryo, T., and Rowe, R. K. (2005). "Hydraulic behaviour of soil-geocomposite layers in slopes." Geosynthetics International, 12(3), 145-155.
Iryo, T., and Rowe, R. K. (2005). "Infiltration into an embankment reinforced by nonwoven geotextiles." Canadian Geotechnical Journal, 42(4), 1145-1159.
Ishikawa, T., Miura, S., and Sekine, E. (2014). "Simple plastic deformation analysis of ballasted track under repeated moving-wheel loads by cumulative damage model." Transportation Geotechnics, 1(4), 157-170.
Ju, S. H., and Kung, J. S. (1997). "Mass types, element orders and solution schemes for the richards equation." Computers and Geosciences, 23, 175-187.
Kao, Y. H., Liu, C. W., Wang, S. W., and Lee, C. H. (2012). "Estimating mountain block recharge to downstream alluvial aquifers from standard methods." Journal of Hydrology, 426–427 93–102.
Kim, J., Jeong, S., Park, S., and Sharma, J. (2004). "Influence of rainfall-induced wetting on the stability of slopes in weathered soils." Engineering Geology, 75(3-4), 251-262.
Kim, K.-M., Briaud, J.-L., Bligh, R., and Abu-Odeh, A. (2012). "Design guidelines and full-scale verification for mse walls with traffic barriers." Journal of Geotechnical and Geoenvironmental Engineering, 138(6), 690-699.
Kim, W. S., and Borden, R. H. (2013). "Numerical simulation of MSE wall behavior induced by surface-water infiltration." Journal of Geotechnical and Geoenvironmental Engineering, 139(12), 2110-2124.
Koerner, R., and Koerner, G. (2010) "A data base and analysis of 141 geosynthetic reinforced mechanically stabilized earth (MSE) walls." Proc., 226th Pennsylvania Geotechnical Conference
Koerner, R. M., and Koerner, G. R. (2011). "The importance of drainage control for geosynthetic reinforced mechanically stabilized earth walls." Journal of GeoEngineering,, 6(1), 3-13.
Koerner, R. M., and Koerner, G. R. (2013). "A data base, statistics and recommendations regarding 171 failed geosynthetic reinforced mechanically stabilized earth (MSE) walls." Geotextiles and Geomembranes, 40, 20-27.
Kool, J. B., and Parker, J. C. (1987). "Development and evaluation of closed form expression for hysteris soil hydraulic properties." Water Resources Research, 23(1), 105-114.
Ku, C.-Y., Hsu, S.-M., Chiou, L.-B., and Lin, G.-F. (2009). "An empirical model for estimating hydraulic conductivity of highly disturbed clastic sedimentary rocks in Taiwan." Engineering Geology, 109(3-4), 213-223.
Kulhawy, F. H., and Mayne, P. W. (1990). "Manual on Estimating Soil Properties for Foundation Design." Electric Power Research Institute, Palo Alto, California
Lade, P. V. (2005). "Single hardening model for soils- parameter determination and typical values." Soil Constitutive Models: Evaluation, Selection, and Calibration, ASCE, ed., 290-309.
Lazarte C. A., Robinson H., Gómez J. E., Baxter A., Cadden A., Berg R. (2015) “Geotechnical Engineering Circular No. 7 Soil Nail Walls - Reference Manual.” US Department of Transportation, Federal Highway Administration, Publication No. FHWA- NHI-14-007
Le Pen, L., Watson, G., Powrie, W., Yeo, G., Weston, P., and Roberts, C. (2014). "The behaviour of railway level crossings: Insights through field monitoring." Transportation Geotechnics, 1(4), 201-213.
Lee, J. H., and Park, H. J. (2015). "Assessment of shallow landslide susceptibility using the transient infiltration flow model and GIS-based probabilistic approach." Landslides, DOI 10.1007/s10346-015-0646-6.
Leroueil, S. (2001). "Natural slopes and cuts: movement and failure mechanisms." Geotechnique, 51(3), 197–243.
Levenberg, E., and Garg, N. (2014). "Estimating the coefficient of at-rest earth pressure in granular pavement layers." Transportation Geotechnics, 1(1), 21-30.
Li, P., Vanapalli, S., and Li, T. (2016). "Review of collapse triggering mechanism of collapsible soils due to wetting. " Journal of Rock Mechanics and Geotechnical Engineering, 8, 256-274
Liu, C. N., Yang, K. H., Ho, Y. H., and Chang, C. M. (2012). "Lessons learned from three failures on a high steep geogrid-reinforced slope." Geotextiles and Geomembranes, 34, 131-143.
Lo, C.-L. (2009). "Study on the Mechanism of Rainfall-Induced Slope Failure and Debris Discharge." Phd, Shu-Te University, Kaoshiung County, Taiwan
Lu, N., and J. Godt. 2008. Infinite slope stability under steady unsaturated seepage conditions. Water Resources Research, 44, W11404.
Lu, N., and Likos, W. J. (2004). "Unsaturated Soil Mechanics", John Wiley & Sons.
Lu, N., and Likos, W. J. (2006). "Suction stress characteristic curve for unsaturated soil." Journal of Geotechnical and Geoenvironmental Engineering, 132(2), 131-142.
Lu, N., Godt, J. W., and Wu, D. T. (2010). "A closed-form equation for effective stress in unsaturated soil." Water Resources Research, 46(5), n/a-n/a.
Mancarella, D., Doglioni, A., and Simeone, V. (2012). "On capillary barrier effects and debris slide triggering in unsaturated layered covers." Engineering Geology, 147-148, 14-27.
Manzari, M. T., and Nour, M. A. (2000). "Significance of soil dilatacny in slope stability analysis." Journal of Geotechnical and Geoenvironmental Engineering, 126(1), 75-80.
Matsumaru, T., and Uzuoka, R. (2016). "Three-phase seepage-deformation coupled analysis about unsaturated embankment damaged by earthquake." International Journal of Geomechanics, 16(5), doi.org/10.1061/(ASCE)GM.1943-5622.0000699.
McCartney, J. S. (2007). "Determination of the Hydraulic Characteristics Of Unsaturated Soils using a Centrifuge Permeameter." Phd Phd, The University of Texas at Austin.
McCartney, J. S., and Zornberg, J. G. (2010). "Effects of infiltration and evaporation on geosynthetic capillary barrier performance." Canadian Geotechnical Journal, 47(11), 1201-1213.
Mikkelsen P.E. (2003). "Advances in inclinometer data analysis." Symposium on Field Measurements in Geomechanics, FMGM 2003, Oslo, 13 pp
Mishra, D., Qian, Y., Huang, H., and Tutumluer, E. (2014). "An integrated approach to dynamic analysis of railroad track transitions behavior." Transportation Geotechnics, 1(4), 188-200.
Mitchell, J. K. (1976). "Fundamentals of Soil Behavior", Wiley, New York.
Mori, T., Uzuoka, R., Chiba, T., Kamiya, K., and Kazama, M. (2011). "Numerical prediction of seepage and seismic behavior of unsaturated fill slope." Soils and foundations, 51(6), 1075–1090.
Morrison K. F., Harrison F. E., Collin J. G., Dodds A., Arndt B. (2006) “Shored Mechanicallystabilized Earth (SMSE) Wall Systems Design Guidelines.” US Department of Transportation, Federal Highway Administration, Publication No. FHWA-CFL/TD-06-001.
Morse, M. S., Lu, N., Wayllace, A., Godt, J. W., and Take, W. A. (2014). "Experimental test of theory for the stability of partially saturated vertical cut slopes." Journal of Geotechnical and Geoenvironmental Engineering, 1-10. DOI: 10.1061/(ASCE)GT.1943-5606.0001119.
Muntohar, A. S., and Liao, H. J. (2010). "Rainfall infiltration: Inifinite slope model for landslides triggering by rainstorm." Natural Hazards, 54, 967-984.
NCMA (2010). "Design Manual For Segmental Retaining Walls" , Herndon, Virginia, USA.
Nogueira, C. L., Azevedo, R. F., and Zornberg, J. G. (2009). Coupled analyses of excavation in saturated soil. International Journal of Geomechanics, 9(2), 73–81.
Nogueira, C. d. L., de Azevedo, R. F., and Zornberg, J. G. (2011). "Validation of coupled simulation of excavations in saturated clay: Camboinhas case history." International Journal of Geomechanics, 11(3), 202-210.
Nuth M. (2009). "Constitutive Modelling of Unsaturated Soils with Hydro-Geomechanical Couplings " , Swiss Federal Institute of Technology in Lausanne, Switzerland
Nuth, M., and Laloui, L. (2008). "Effective stress concept in unsaturated soils." International Journal for Numerical and Analytical Methods in Geomechanics, 32, 771–801.
Oh, S., and Lu, N. (2015). "Slope stability analysis under unsaturated conditions: Case studies of rainfall-induced failure of cut slopes." Engineering Geology 184, 96–103.
Oloo, S. Y., and Fredlund, D. G. (1996). "A method for determination of phi(b) for statically compacted soils." Canadian Geotechnical Journal, 33(2), 272-280.
Pachri, H., Mitani, Y. , Ikemi, H. and Jiang, W. (2015). "Spatial variation of soil depth and shallow slope failures in Sangun mountains, Fukuoka Prefecture, Japan." International Journal of Geosciences, 6, 813-820.
Patki, M., Dewaikar, D., and Mandal, J. N. (2016). "Numerical evaluation of passive earth-pressure coefficients under the effect of surcharge loading." International Journal of Geomechanics, DOI: 10.1061/(ASCE)GM.1943-5622.0000736.

Polemio, M.; Petrucci, O. (2000). “Rainfall as a landslide triggering factor: an overview of recent international research.” The 8th International Symposium on Landslides in Cardiff in the year 2000, June 2000, E. Bromhead, N. Dixon and M.L. Ibsen Eds., 3, 1219-1226.
Qi, S., and Vanapalli, S. K. (2015). "Hydro-mechanical coupling effect on surficial layer stability of unsaturated expansive soil slopes." Computers and Geotechnics 70, 68–82.
Raisinghani, D. V., and Viswanadham, B. V. S. (2011). "Centrifuge model study on low permeable slope reinforced by hybrid geosynthetics." Geotextiles and Geomembranes, 29(6), 567-580.
Rasekh, A., Hassanzadeh, A., Mulchandani, S., Modi, S., and Banks, M. K. (2016). "Smart water networks and cyber security." Journal of Water Resources Planning and Management, 142(7), 01816004.
Reynolds, W. D., Elrick, D. E., and Clouthier, B. E. 1985. "The constant head well permeameter: Effect of unsaturated flow." Soil Science, 139, 172–180
Reynolds, W. D., Elrick, D. E., Baumgartner, N., and Clothier, B.E. 1984. "The Guelph Permeameter for measuring the field-saturated hydraulic conductivity above the water table: 2. The apparatus." In Proceedings of Canadian Hydrology Symposium
Richards, L. A. (1931). "Capillary conduction of liquids through porous mediums " Physics, 1, 318-333.
Rojas, E., Pérez-Rea, M., López-Lara, T., Hernández, J., and Horta, J. 2015. Use of effective stresses to model the collapse upon wetting in unsaturated soils. Journal of Geotechnical Geoenvironmental Engineering, 10.1061/(ASCE)GT.1943-5606.0001251, 04015007.
Romano, N., D'Urso, G., Severino, G., Chirico, G. B., Palladino, M., Chirico, G. B., Borga, M., Tarolli, P., Rigon, R., and Preti, F. (2013). "Four decades of progress in monitoring and modeling of processes in the soil-plant-atmosphere system: applications and challengesrole of vegetation on slope stability under transient unsaturated conditions." Procedia Environmental Sciences, 19, 932-941.
Sáez, E., and Ledezma, C. (2015). "Liquefaction mitigation using secant piles wall under a large water tank." Soil Dynamics and Earthquake Engineering, 79, 415-428.
Sánchez, M., Wang, D., Briaud, J.-L., and Douglas, C. (2014). "Typical geomechanical problems associated with railroads on shrink-swell soils." Transportation Geotechnics, 1(4), 257-274.
Santacana, N., Baeza, B., Corominas, J., Paz, A. d., and Marturia, J. (2003). "A GIS-based Multivariate statistical analysis for shallow landslide suscheptibility mapping in a La Pobla de Lillet area (Eastern Pyrenees, Spain)." Natural Hazards 30, 281–295.
Schanz, T., and Al-Badran, Y. (2014). "Swelling pressure characteristics of compacted Chinese Gaomiaozi bentonite GMZ01." Soils and Foundations, 54(4), 748-759.
Schanz, T., Vermeer, P. A., and Bonnier, P. G. (1999). "The hardening soil model-Formulation and verification." Beyond 2000 in Computational Geotechnics- 10 Years of PlaxisBalkema, Rotterdam, 1-16.
Schmertmann, J.H. 1970. Static cone to compute static settlement over sand. Journal of the Soil Mechanics and Foundations Division, ASCE, 96(SM3), 1011-1043
Sheng, D. (2011). "Review of fundamental principles in modelling unsaturated soil behaviour." Computers and Geotechnics, 38(6), 757-776.
Sheng, D., Gens, A., Fredlund, D. G., and Sloan, S. W. (2008). "Unsaturated soils: From constitutive modelling to numerical algorithms." Computers and Geotechnics, 35 810–824.
Sreedeep, S., and Singh, D. N. (2011). "Critical review of the methodologies employed for soil suction measurement." International Journal of Geomechanics, 11(2), 99-104.
Stark, T. D. and Choi, H. 2008. Slope inclinometers for landslides. Landslides 5:339–350
Stark, T. D., Zhindon, J. S. L., and Baghdady, A. K. (2016). "Unsaturated and transient seepage analysis of San Luis dam." RocNews, Spring 2016, 1-14.
Surarak, C., Likitlersuang, S., Wanatowski, D., Balasubramaniam, A., Oh, E., and Guan, H. (2012). "Stiffness and strength parameters for hardening soil model of soft and stiff Bangkok clays." Soils and Foundations 52(4), 682–697.
Tani, K., Kiyota, T., Matsushita, K., Hashimoto, T., Yamamoto, A., Takeuchi, H., Noda, T., Kiku, H., and Obayashi, J. (2015). "Liquefaction countermeasures by shallow ground improvement for houses and their cost analysis." Soil Dynamics and Earthquake Engineering, 79, 401-414.
Thuo, J.N., Huynh, V.D.A., Yang, K-H, and Portelinha, F.H.M., (2016). “Behavior of Geotextile- and Geogrid-Reinforced Soil Slopes with Various Backfills Subject to Rainfalls”, Proceedings of the 6th Asian Regional Conference on Geosynthetics, Geosynthetics Asia 2016, Deli, India, November 2016.
Thuo, J. N., K.H.Yang, and Huang, C. C. (2015). "Infiltration into unsaturated reinforced slopes with nonwoven geotextile drains sandwiched in sand layers." Geosynthetics International, 22(6), 457–474.
Tofani, V., Dapporto, S., Vannocci, P., and Casagli1, N. (2006). "Infiltration, seepage and slope instability mechanisms during the 20–21 November 2000 rainstorm in Tuscany, central Italy." Natural Hazards and Earth System Sciences, 6, 1025–1033.
Travis Q. B., Houston, S.L., Marinho F. A. M, Schmeeckle M. (2010). "Unsaturated infinite slope stability considering surface flux conditions." Journal of Geotechnical and Geoenvironmental Engineering, 136(7), 963–974
Tschuchnigg, F., Schweiger, H. F., and Sloan, S. W. (2015). "Slope stability analysis by means of finite element limit analysis and finite element strength reduction techniques. Part I: Numerical studies considering non-associated plasticity." Computers and Geotechnics, 70, 169-177.
Urciuoli, G., Pirone, M., Comegna, L., and Picarelli, L. (2016). "Long-term investigations on the pore pressure regime in saturated and unsaturated sloping soils." Engineering Geology, 212, 98-119.
Valentine, R. J. "An assessment of the factors that contribute to the poor performance of geosynthetic-reinforced earth retainingwalls." Proceedings of Design and Practice of Geosynthetic-Reinforced Soil Structures DEStech Publications, Inc., United States of America, 318-327.
van Genuchten, M. T. (1980). "A closed form equation for predicting the hydraulic conductivity of unsaturated soils." Soil Science Society of America Journal, 44(5), 892-898.
Vanapalli, S. K., Fredlund, D. G., and Pufahl, D. E. (1996). "The relationship between the soil-water characteristic curve and the unsaturated shear strength of a compacted glacial till." Geotechnical Testing Journal, 19(3), 259-268.
Vanapalli, S. K., Fredlund, D. G., Pufahl, D. E., and Clifton, A. W. (1996). "Model for the prediction of shear strength with respect to soil suction." Canadian Geotechnical Journal, 33(3), 379-392.
Vandenberge D.R., Duncan J.M, Brandon T.L. 2015 Limitations of transient seepage analyses for calculating pore pressures during external water level changes. Journal of Geotechnical and Geoenvironmental Engineering, ASCE , 141(1), 1–10
Viana da Fonseca, A., Amaral, M. F., Panico, F., and Rios, S. (2014). "Indexation of dynamic and static geomechanical properties of a cemented aggregate for transportation engineering." Transportation Geotechnics, 1(1), 31-44.
Woodward, P. K., Kennedy, J., Laghrouche, O., Connolly, D. P., and Medero, G. (2014). "Study of railway track stiffness modification by polyurethane reinforcement of the ballast." Transportation Geotechnics, 1(4), 214-224.
Wu, L. Z., Zhang, L. M., and Li, X. (2015). "One-dimensional coupled infiltration and deformation in unsaturated soils subjected to varying rainfall." International Journal of Geomechanics, 1-6. DOI: 10.1061/(ASCE)GM.1943-5622.0000535.
Wu, Y. M., Lan, H. X., Gao, X., Li, L. P., and Yang, Z. H. (2015). "A simplified physically based coupled rainfall threshold model for triggering landslides." Engineering Geology, 195, 63-69.
Wulfsohn, D., Adams, B. A., and Fredlund, D. G. (1996). "Application of unsaturated soil mechanics for agricultural conditions." Canadian Agricultural Engineering, 38(3), 173-181.
Xue, J. and Chen, J. J. (2015), "Reinforcement strength reduction in FEM for mechanically stabilized earth structures" Journal of Central South University, 22 (7), 2691−2698.
Yang, K.-H., Yalew, W. M., and Nguyen, M. D. (2015). "Behavior of geotextile-reinforced clay with a coarse material sandwich technique under unconsolidated-undrained triaxial compression." International Journal of Geomechanics and Engineering, 16 (3), DOI: 10.1061/(ASCE)GM.1943-5622.0000611.
Yang, K-H, Nguyen, M.D., Yalew, W.M., Liu, C-N, and Gupta, R. (2016). "Behavior of geotextile-reinforced clay under consolidated-undrained tests: Reinterpretation of porewater pressure parameters." Journal of GeoEngineering, 11(2), 45-57.
Yonezawa, T., Yamazaki, T., Tateyama, M., and Tatsuoka, F. (2014). "Design and construction of geosynthetic-reinforced soil structures for Hokkaido high-speed train line." Transportation Geotechnics, 1(1), 3-20.
Yoo, C., and Jung, H.-Y. (2006). "Case history of geosynthetic reinforced segmental retaining wall failure." Journal of Geotechnical and Geoenvironmental Engineering, 132(12), 1538-1548.
Zhang, L. L., Fredlund, D. G., Fredlund, M. D., and Wilson, G. W. (2014). "Modeling the unsaturated soil zone in slope stability analysis." Canadian Geotechnical Journal, 51, 1384–1398
Zhang, L. L., Zhang, L. M., and Tang, W. H. (2005). "Rainfall-induced slope failure considering variability of soil properties." Geotechnique, 55(2), 183–188.
Zhang, Y., Ishikawa, T., Tokoro, T., and Nishimura, T. (2014). "Influences of degree of saturation and strain rate on strength characteristics of unsaturated granular subbase course material." Transportation Geotechnics, 1(2), 74-89.
Zornberg, J. G., Bouazza, A., and McCartney, J. S. (2010). "Geosynthetic Capillary Barriers: Current State of Knowledge." Geosynthetics International, 17(5), 273-300.
Zornberg, J. G., and Mitchell, J. K. (1994). "Reinforced soil structures with poorly draining backfills. part i:reinforcement interactions and functions." Geosynthetics International, 1,No. 2, 103-148.