an official journal of: published by:
Editor in Chief: RAFFAELLO COSSU


  • Daniele Cazzuffi - CESI SpA , Italy
  • Piergiorgio Recalcati - TENAX SpA , Italy
  • Lidia Sarah Calvarano - TENAX SpA , Italy
  • Stefano Marelli - TENAX SpA , Italy

DOI 10.31025/2611-4135/2022.15219

Released under CC BY-NC-ND

Copyright: © 2022 CISA Publisher

Editorial History

  • Received: 25 Feb 2022
  • Revised: 17 Jun 2022
  • Accepted: 29 Aug 2022
  • Available online: 30 Sep 2022


One of the crucial aspects in design of a landfill capping is the interface behavior between the different layers of the cover system, from levelling layer above waste up to the topsoil. Design guidelines and international codes require a geotechnical stability analysis to be performed along every interface. The critical interface is the one which gives the minimum shear resistance, in terms of friction angle and adhesion. Evaluation of the correct values to be used is then essential. Shear resistance at the interface between different geosynthetics or between a geosynthetic and a soil can be measured through laboratory tests. Testing methods are EN ISO 12957-1 and ASTM D5321 (for direct shear test) and EN ISO 12957-2 (for inclined plane). The paper briefly describes direct shear and inclined plane testing methods and enhances pros and cons. In the last 25 years the authors have coordinated a great number of the above tests with different types of geosynthetics and soils. The main results of these tests are reported in the paper, summarizing the values obtained with contact interface between different products belonging to the same families. The purpose of this work is to validate the already big database of interface strength measured with direct shear tests and to evaluate the differences with the results obtained for the different types of tests. This can give to designers the chance to have a critical approach toward the most suitable testing method to be used according to the specific needs of a project.



ASTM D5321/D5321M, 2017. Standard Test Method for Determining the Shear Strength of Soil-Geosynthetic and Geosynthetic-Geosynthetic Interfaces by Direct Shear

ASTM D7702/D7702M, 2021. Standard Guide for Considerations When Evaluating Direct Shear Results Involving Geosynthetics

Atkinson, J. H., and Farrar, D. M.,1985. Stress path tests to measure soil strength parameters for shallow landslips. Proc., 11th Int. Conf. on Soil Mech. and Found. Eng., Golden Jubilee Volume, Taylor and Francis, London, Vol. 2, pp. 983– 986

Bacas, B.M., Cañizal, J., Konietzky, H., 2015. Shear strength behavior of geotextile/geomembrane interfaces. Journal of Rock Mechanics and Geotechnical Engineering, Vol. 7 , pp. 638-645

Baker, R., 2004. Non-linear strength envelopes based on triaxial test data. J. Geotech. Geoenv. Eng., Vol. 130 (5), pp. 498- 506

Bishop, A. W., Webb, D. L., and Lewin, P. I. , 1965. Undisturbed samples of London clay from the Ashford common shaft: strength-effective normal stress relationship. Géotechnique, Vol. 15 (1), pp. 1-31

BS EN 1997-1, 2004. Eurocode 7: Geotechnical design - Part 1:General Rules

BS EN 1998-5, 2004.Eurocode 8. Design of structures for earthquake resistance -Part 5: Foundations, retaining structures and geotechnical aspects

Cazzuffi, D., Recalcati, P., 2018. Recent developments on the use of drainage geocomposites in capping systems, Detritus. Multidisciplinary Journal for Waste Resources & Residues, CISA Publisher, Vol. 3, pp. 93-99

Das, B. M.,1990. Principles of Geotechnical Engineering, 2nd edition, PWS-Kent, Boston

Dixon, N., Jones, D. R. V., Fowmes, G. J., 2006. Interface shear strength variability and its use in reliability-based landfill stability analysis. Geosynthetics International, Vol 13, No. 1, pp. 1–14

Day, R. W., and Maksimovic, M., 1994. Stability of compacted clay slopes using a nonlinear failure envelope. Bulletin of the Assoc. of Eng. Geologists, Vol. 31 (4), pp. 516-520

Duncan, J.M., Brandon, T.L., VandenBerge, D.R., 2011. Report of the workshop on shear strength for stability of slopes in highly plastic clays, CGPR #67. Center for Geotechnical Practice and Research, Blacksburg

EN ISO 12957-1, 2018. Geosynthetics - Determination of friction characteristics - Part 1: Direct Shear Test. European Committee for Standardization, CEN, Brussels, Belgium

EN ISO 12957-2, 2005. Geosynthetics - Determination of friction characteristics - Part 2: Inclined plane test. European Committee for Standardization, CEN, Brussels, Belgium

Gamez, J.A., Stark, T.D., 2014. Fully softened shear strength at low stresses for levee and embankment design. J Geotech Geoenviron Eng, Vol. 140:1–6

Grossule, V., Stegmann, R., 2020. Problems in traditional landfilling and proposals for solutions based on sustainability. Detritus, Vol. 12, pp. 78–91.
DOI 10.31025/2611-4135/2020.14000

Holtz, W. G., and Gibbs, H. J., 1956. Shear strength of pervious gravelly soils. J. Soil. Mech. Found. Div., Vol. 82 (SM 1), pp. 1-22

Koerner, R. M., Koerner, G. R., 2007. Interpretation(s) of Laboratory Generated Interface Shear Strength Data. GRI White Paper #11,Geosynthetic Research Institute, p. 8

Koerner, G.R., Narejo, D., 2005. Direct Shear Database of Geosynthetic-to-Geosynthetic and Geosynthetic-to-Soil Interfaces. GRI Report #30, p. 112

Lancellotta, R. 1995. Geotechnical Engineering. CRC Press. Pp. 448

Lefebvre, G.,1981. Strength and slope stability in Canadian soft clay deposits. Can. Geotech. J., Vol.18 (3), pp. 420-442

Maksimovic, M., 1989. Nonlinear failure envelope for soils. J. Geotech.Geoenv. Eng., Vol. 115 (4), pp. 581-586

Mesri ,G., Shahien, M., 2003. Residual shear strength mobilized in first-time slope failures. J Geotech Geoenviron Eng, Vol. 129, pp. 12–31

Marsland, A., 1971. The shear strength of stiff fissured clays. Proc., Roscoe Memorial Symp., Cambridge University, Cambridge, England, pp. 59-68

Moraci, N., Cardile, G., Gioffrè, D., Mandaglio, M.C., Calvarano, L.S., Carbone, 2014. Soil geosynthetic interaction: design parameters from experimental and theoretical analysis. Transportation Infrastructure Geotechnology Vol.1, n. 2, pp.165-227, Ed. Springer

Noor, M.J.M., Hadi, B.A., 2010. The role of curved-surface envelope Mohr–Coulomb model in governing shallow infiltration induced slope failure. Electron J Geotech Eng, Vol. 15, pp.1–21

Penman, A.,1953. Shear characteristics of saturated silts measured in triaxial compression. Géotechnique, Vol 3 (8), pp.312-328

Ponce, V. M., and Bell, J. M., 1971. Shear strength of sand at extremely low pressures. J. Soil Mech. Found. Div., Vol. 97 (SM4), 625-637

Stark, T. D., Choi, H., 2003. Peak versus residual interface strengths for landfill liner and cover design, Geosynthetics. Harbin Inst. Technol. 46

Terzaghi, K, Peck, R.B., Mesri, G., 1996. Soil mechanics in engineering practice, 3rd edn. Wiley, New York

Vesic, A. S., and Clough, G. W., 1968. Behaviour of granular materials under high stresses. J. Soil Mech. Found. Div., Vol. 94 (SM3), pp. 661-688

Wright, S.G., 2005. Evaluation of soil shear strengths for slope and retaining wall stability analyses with emphasis on high plasticity clays. Center for Transportation Research, University of Texas at Austin