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The Influence of Biofilm on the Mechanical Behavior of Sand S. W. Perkins,1 P. Gyr,2 and G. James3 REFERENCE: Perkins, S. W., Gyr, P., and James, G., “The Influence of Biofilm on the Mechanical Behavior of Sand,” Geotechnical Testing Journal, GTJODJ, Vol. 23, No. 3, September 2000, pp. 300–312. ABSTRACT: The growth of microbes on the surface of an object results in the formation of a biofilm, which in sand can lead to a reduction of hydraulic conductivity and can be used for groundwater containment and remediation. Sample preparation and testing techniques for triaxial and oedometer experiments were devised for the purpose of examining the influence of biofilm on the stress-straintime properties of Ottawa sand. Results have shown that biofilm has a negligible influence on the strength and stiffness of the sand but increases time-dependent creep deformation. An elasto-viscoplastic constitutive model was calibrated for biofilm and non-biofilm sand and implemented into a finite-element code for the purpose of predicting creep deformation of a slope and a foundation resting on level ground. Numerical simulations showed that additional creep behavior of the biofilm sand had a negligible influence on the behavior of these geotechnical engineering facilities. KEYWORDS: microbial bacteria, biofilm, biobarrier, sand, triaxial testing, oedometer testing, mechanical behavior, creep, constitutive modeling, finite-element modeling GTJ11052J.6514.pdf