Influence of Specimen Size in Engineering Practice

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Abstract
A combined laboratory experimental and numerical analysis is presented to investigate the influence of specimen size and scale effect on engineering analysis and design. Laboratory triaxial compression and direct shear tests show that the size of the specimen has a significant influence on the stress-strain behavior of sands with larger specimens mobilizing smaller shear strengths. Shear strengths measured in laboratory direct shear tests are incorporated in FEM and slope-stability analyses to evaluate and compare the shear stress distribution and deformational behavior of a slope case study. The numerical analyses are conducted using ABAQUS and Mohr-Coulomb failure criteria. The performance of the slope under load application due to staged highway embankment construction is also evaluated. The analyses results show that the shear stresses and performance of slope and highway embankment are influenced considerably by the size of the triaxial specimens. This would have significant implications on engineering design and the choice of a representative sample size. To apply the shear strengths in design, it is suggested to employ larger specimen sizes to achieve the critical state strengths of the soil and better representation of field deformations.

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