Research Review Report on Effect of Specimen Size on Shear Strength of Soil in Laboratory Test

EasyChair Preprint 9599

Abstract

This Research Review report highlights the various specimen size in triaxial test from smaller to bigger diameter (i.e., 30 to 110 mm dia.) adopted by several international codes and standards to determine shear strength parameters under different drainage condition. The influence of specimen size and its scale effect studied by various researchers are presented and discussed in literature review. It cannot be disregarded that smaller specimen can achieve good amount of consolidation and higher compressibility as compared to bigger specimen. Consequently shear strength may increase with decrease in specimen size. The choice of bigger sample size is thus a more accurate representation of soil strength conditions with respect to field deformation. BIS codes has also provided flexibility to use four different specimen size from smaller to bigger diameter (D) i.e., 38, 50, 70, 100 mm to determine shear strength parameters in triaxial apparatus.

The lower deviator stresses in the bigger specimens is associated with the more intense strain softening resulting from shearing which may be due to smaller compressibility behavior as compared to smaller specimen.

Study on effect of specimen size on pre-peak, peak and post peak stress behavior with respect to strain can uncover major discrepancies when tested in smaller specimen. Smaller specimen may develop migration of pore water pressure quickly as compared to bigger specimen. Pore water pressure under shearing may differs by specimen size due to which, large difference in the effective stress paths can be observed. To reduce specimen size effect on smaller specimen with respect to shear strength parameters, a correction factor related to size effect can be proposed with extensive testing program. This will help to assign appropriate shear strength parameters for better representation of field soil behavior.

Keyphrases: Triaxial, diameter, shear strength

@booklet{EasyChair:9599,
  author    = {Maurya Suresh Seopal},
  title     = {Research Review Report on Effect of Specimen Size on Shear Strength of Soil in Laboratory Test},
  howpublished = {EasyChair Preprint 9599},
  year      = {EasyChair, 2023}}