An Investigation into a Geocell-reinforced Slope in the Unsaturated Numerical Model
الموضوعات :Behnam Mehdipour 1 , Hamid Hashemalhosseini 2 , Bahram Nadi 3 , Masoud Mirmohammad Sadeghi 4
1 - Department of Civil Engineering , Najafabad Branch, Islamic Azad University ,Najafabad,Iran
2 - Civil Engineering Department, Isfahan University of Technology, Isfahan, Iran
3 - Department of Civil Engineering , Najafabad Branch, Islamic Azad University ,Najafabad,Iran
4 - Faculty of Civil Engineering, Isfahan Higher Education and Research Institute, Isfahan,Iran
الکلمات المفتاحية: Geocell, Unsaturated soil, Barcelona Basic Model, suction, FLAC2D,
ملخص المقالة :
Considering unsaturation conditions of soil significantly helps to produce relatively real results. Numerical methods have been assumed as conventional methods in soil mechanics to examine soil behavior. However, the accuracy of numerical methods dramatically depends on applying the appropriate behavioral model to solve problems. One of the known elastoplastic models for unsaturated soils is the Barcelona Basic Model which is added to FLAC2D software through codification. Geocell-reinforced slope functions as a beam in the soil due to the three dimensional nature of the reinforcement, i.e. height is included. Furthermore, the reinforcement causes a reduction in slope displacement and an increase in the factor of safety of slope due to its bending characteristics including moment of inertia and consequently bending strength. Moreover, soil unsaturated conditions are applied to the modelling and suction variations in soil are incorporated. This makes the maximum horizontal displacement of slope occur in the upper part of the Geocell layer while the horizontal displacement values for the slope height are substantially reduced below the Geocell layer. Increasing suction, geocell axial force declines by at most 18.5%. As overhead pressure increases, there is an increase in the force concentrated at the soil-geocell interface and the tensile force is consequently enlarged in reinforcements.
[1]Sheng,D.,"Review of fundamental principles in modelling unsaturated soil behavior";Computers and Geotechnics; 38, pp.757-776,(2011).
[2]Sheng,D.,"Constitutive Modelling of Unsaturated Soils: Discussion of Fundamental Principles."; Unsaturated soils; 1, 91-112,(2011).
[3] Sangseom,J.Yongmin,K,“ Effects of rainfall infltration and hysteresis on the settlement of shallow foundations in unsaturated soil”; Environmental Earth Sciences, 77:494 (2018).
[4]Fredlund,D.G.,MorgensternN.R.,WidgerA.,"Shear strength of unsaturated soils"; Can.Geotech. J; 15, pp.313–321,(1978).
[5] Wu LZ, Huang RQ, Xu Q, Zhang LM, Li HL.,” Analysis of physical testing of rainfall-induced soil slope failures”. Environ Earth Sci 73:8519–8531, (2015).
[6]Oberg, A. L., Sallfors, G.A.,"rational approach to the determination of the shear strengthparameters of unsaturated soils"; Proc. 1st Intl Conf. Unsaturated Soils, Paris, pp.151-158,2, pp. 279-289,(1996).
[7] Kim Y, Jeong S, Kim J .Coupled infltration model of unsaturated porous media for steady rainfall. Soils Found 56(6):1073–1083, (2016).
[8] Ma T, Li C, Lu Z, Bao Q.,”Rainfall intensity–duration thresholds for the initiation of landslides in Zhejiang Province”,China. Geomorphology 245:193–206, (2015).
[9]Khalili, N., Khabbaz, M. H.,"A uniquerelationship for χ for the determination of theshear strength of unsaturated soils";Geotechnique; 48, No .5, pp.681-687,(1998).
[10] Alonso, E.E., Gens, A., josa, A., "A constitutive model for partially saturated soils" Geotechnique;40, pp.405-430, (1990).
[11]M.Isabel,M.Pinto,T.W.Cousens.,“Geotextile Reinforced Brick Faced Retaining Walls”,Geotextiles and Geomembranes, 14 - 449-464,(1996).
[12] Wu LZ, Selvadurai APS .Rainfall infltration-induced groundwater table rise in an unsaturated porous medium. Environ EarthSci 75(2):1–11,(2016)
[13]Graeme,D.Skinner,R. Kerry Roweb,”Design and behaviour of a geosynthetic reinforced retaining wall and bridge abutment on a yielding foundation”, Geotextiles and Geomembranes,23( 3), pp.234-260,(2005).
[14] Jorg G. Zornberg, Nicholas Sitar, James K. Mitchell, Honorary Member.,“ Perfprmance of Geosynthetic Reinforced Slopes at Failure ”, Journal of Geotechnical and Geoenvironmental Engineering, (1998).
[15]Jorge,G.Zornberg,M.ASCE,Fabiana Arriag.,“Strain Distribution with in Geosynthetic-Reinforced Slopes”,Journal of Geotechnical and Geoenvironmental Engineering, 129(1),32-45,(2003).
[16]Lazhar, B., Hacene B., Jarir Y. “Internal Stability Analysis of Reinforced Earth Retaining Walls”,Geotech Geol Eng, 29:443–452,(2011).
[17]Chen,R.H.,Chiu,Y.M."Model Tests of Geocell Retaining Structures",Geotextilesand Geomembranes 26(1),pp.56-70,(2008).
[18]Chen,R.H., Huang, Y.W., Huang, F,C. ," Confinement Effect of Geocells on Sand Samples Under Triaxial Compression",Geotextiles and Geomembranes,37(1), pp. 35-44,(2013).
[19] Fakher A. and Jones C.J.F.P.,"When the bending stiffness of geosyntheticreinforcement is important". Geosynthetics International, 8, No. 5, 445–460,(2001)
[20] Zhang L, Zhao MH, Zou XW, Zhao H., "Deformation analysis of geocellreinforcement using winkler model". Comput Geotech;36:977–83,(2009).
[21] Zhang, L., Zhao, M.H., Zou X.W. and Zhao, H., “Analysis of geocellreinforcedmattress with consideration of horizontal vertical coupling” .ComputGeotech, 37, 748–56,(2010).
[22]Dash, S.K., Rajagopal, K., Krishnaswamy, N.R," Behaviour of geocellreinforced sand beds under strip loading". Canadian Geotechnical Journal 44,905–916, (2007).
[23]Yang, X. M., Han, J., Parsons, R. L., and Leshchinsky, D., "Threedimensional numerical modeling of single geocell-reinforced sand." Front.Archit. Civ. Eng. China, 4(2), 233–240,(2010).
[24]Van Genuchten MY.,” A closed form equation for predicting the hydraulic conductivity of unsaturated soils”. Soil Sci Soc Am J 44:892–898,(1980).
[25]Sreedeep S, Singh DN., “ Nonlinear curve-fitting procedures for developing Soil-water characteristic curves”. Geotech Test J 29(5):409–418,(2006).
[26] Y.M. Cheng a, T. Lansivaara b, W.B. Wei."Two-dimensional slope stability analysis by limit equilibrium and strength reduction method"s. Computers and Geotechnics 34, 137–150,(2007).
[27] Madhavi Latha, G., Rajagopal, K. and Krishnaswamy, N.R.“Experimental and theoretical investigations on geocell supported embankments” International Journal of Geomechanics. ASCE, Vol.6, pp.30-35,(2006).
[28]Mehdipour, I., Ghazavi, M., Moayed, R.Z. "Numerical study on stability analysis of geocell reinforced slopes by considering the bending effect". Geotext. Geomembr. 37, 23e34,(2013).
