A. Arab

H. Missoum

M. Belkhatir

N. Della

T. Schanz

Comptes Rendus Mécanique (CRM)

C. R. Mecanique 339 (2011) 63–66Contents lists available at ScienceDirectComptes Rendus Mecaniquewww.sciencedirect.comReply to the comment by M. Rahman on “Influence of inter-granular voidratio on monotonic and cyclic undrained shear response of sandy soils”by M. Belkhatir et al. [C. R. Mecanique 338 (2010) 290–303]M. Belkhatir a,∗, H. Missoum b, A. Arab a, N. Della a, T. Schanz ca Laboratory of Materials Sciences & Environment, University of Chlef, BP 151, route de Sendjes, 02000 Chlef, Algeriab Laboratory of Construction, Transports and Environment Protection, University of Mostaganem, Algeriac Laboratory of Foundation Engineering, Soil & Rock Mechanics, Ruhr University of Bochum, Germanya r t i c l e i n f oArticle history:Available online 26 January 2011The authors would like to thank M. Rahman for his comment on our work, and for trying to establish new correlationsin term of the equivalent void ratio for a range of 0–33% of fines content.In his commentary, the author focuses his discussion on the use of the equivalent void ratio instead of the inter-granularvoid ratio. Certainly, the equivalent void ratio cited and detailed by many researchers offers many advantages, especiallyin evaluating the determination of the fines fraction participating in force chain of the soil mixture. Moreover, a uniquefunction of dilatancy can be established for a certain range of fines content where the equivalent void ratio is a stateparameter.In our Note, three different types of samples (loose, medium dense and dense) are investigated with non-plastic finescontent ranging from 0 to 50%. In our tests, the undrained shear strength was evaluated from monotonic consolidatedundrained triaxial tests on reconstituted samples.Indeed, experimental tests on silty sands reported by Zlatovic and Ishihara [1], and Thevanayagam et al. [2] demonstratedthat deformation characteristics and pore water generated in samples with non-plastic fines content were quite differentfrom clean sands and the steady state decrease until 30% of fines content and the pore water generation is maximum atcritical fines content. It is recognized that the threshold fines content (Fthre) is evaluated from the turning point of thereverse movement of the steady state line (SSL).We may not agree with the author when he reported that our Fig. 11 (reproduced here) showed a reversal trend onshear strength at phase transition in between 30% to 40% fines content. Fig. 11 shows clearly that the undrained shearstrength at the phase transition decreases with the decrease of the global void ratio and the increase of the fines contentfor all densities (Dr = 12, 50 and 90%). Beyond Fc = 30%, the undrained shear strength at the phase transition continues todecrease with the increase of the global void ratio and fines content. Based on that, we can say that the global void ratio isnot a pertinent parameter to be used for liquefaction analysis of sand-silt mixtures. Therefore, the inter-granular void ratio(Kenny [3]; Kuerbis et al. [4]; Mitchell [5]) was introduced to explain liquefaction behavior of such soils and was consideredas a state parameter (Belkhatir et al. [6]).Contrary to what was written in the commentary, we think that the interpretation of the data up to 50% fines con-tents in terms of es is reasonable. They should be better interpreted with es provided that Fc  50%. The threshold finesDOI of original article: 10.1016/j.crme.2010.12.009.* Corresponding author.E-mail address: abelkhatir@yahoo.com (M. Belkhatir).1d631-0721/$ – see front matter © 2011 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.oi:10.1016/j.crme.2011.01.00164 M. Belkhatir et al. / C. R. Mecanique 339 (2011) 63–66Fig. 11. Undrained shear strength at the phase transition point versus global void ratio and fines content (σ ′3 = 100 kPa).Fig. 7. Influence of the fines content on the undrained response of the sand-silt mixtures (σ ′3 = 100 kPa, Dr = 12%).Fig. 8. Influence of the fines content on the undrained response of the sand-silt mixtures (σ ′3 = 100 kPa, Dr = 50%).M. Belkhatir et al. / C. R. Mecanique 339 (2011) 63–66 65Fig. 9. Influence of the fines content on the undrained response of the sand-silt mixtures (σ ′3 = 100 kPa, Dr = 90%).Fig. 13. Normalized undrained shear strength at the phase transition point versus inter-granular void ratio (σ ′3 = 100 kPa).content parameter introduced by the author in the commentary for Chlef sand (Fthre = 33%) is not consistent with Fig. 11.Indeed, our results (Figs. 7, 8 and 9, reproduced here) did not confirm the existence of the reversal trend up to 50% finescontent.Fig. 1 of Rahman [7] does not bring any new information concerning the tendency of the sand-silt mixtures comparedto our Fig. 13. Moreover, it fails to predict undrained shear strength at phase transition for higher fines contents.Formula (6) of [7] is questionable since there is not enough information on steady state, available in the publishedliterature.One of the advantages of our results is that the relationships obtained in term of inter-granular void ratio for undrainedshear strength at phase transition are valid till 50% fines content. However, the relationship expressed in term of the equiv-alent void ratio by the author seems to be valid till 33% of fines content. Also, it is important to notice that the undrainedshear strength is getting lower beyond the limiting value of fines content Fthre proposed by the author.In our future investigations, we are seeking Fthre (point of reversal trend) using the formula (6) of [7] with new fittingparameters in order to generalize our study for a wide range of fines contents.References[1] S. Zlatovic, K. Ishihara, On the influence of non plastic fines on residual strength, in: Proc. 1st Int. Conf. on Earthquake Eng., Tokyo, 1995, pp. 239–244.[2] S. Thevanayagam, K. Ravishankar, S. Mohan, Effect of fines on monotonic undrained shear strength of sandy soils, Geotechnical Testing J. 20 (4) (1997)394–406.[3] T.C. Kenny, Residual strengths of mineral mixtures, in: Proc., 9th Int. Conf. Soil Mech. and Found. Eng., Tokyo, vol. 1, 1997, pp. 155–160.66 M. Belkhatir et al. / C. R. Mecanique 339 (2011) 63–66[4] R. Kuerbis, D. Nagussey, Y.P. Vaid, Effect of gradation and fines content on the undrained response of sand, in: Proc. Hyd. Fill. Struc. Geotech. Spec. Publ.,vol. 21, ASCE, New York, 1988, pp. 330–345.[5] J.K. Mitchell, Fundamental of Soil Behaviour, 2nd ed., John Wiley Inter-science, New York, 1993.[6] M. Belkhatir, A. Arab, N. Della, H. Missoum, T. Schanz, Influence of inter-granular void ratio on monotonic and cyclic undrained shear response of sandysoils, C. R. Mecanique 338 (2010) 290–303.[7] M. Rahman, Comment on: “Influence of inter-granular void ratio on monotonic and cyclic undrained shear response of sandy soils” by M. Belkhatir,A. Arab, H. Missoum, T. Schanz [C. R. Mecanique 338 (2010) 290–303], C. R. Mecanique 339 (1) (2011) 58–62, doi:10.1016/j.crme.2010.12.009.

Reply to the comment by M. Rahman on “Influence of inter-granular void ratio on monotonic and cyclic undrained shear response of sandy soils” by M. Belkhatir et al. [C. R. Mecanique 338 (2010) 290–303]

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Reply to the comment by M. Rahman on “Influence of inter-granular void ratio on monotonic and cyclic undrained shear response of sandy soils” by M. Belkhatir et al. [C. R. Mecanique 338 (2010) 290–303]

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