Amir Hamidi, Ali Dehghan,
Volume 9, Issue 2 (9-2015)
Abstract
This paper describes triaxial compression tests conducted to determine the effect of fiber inclusion on stiffness and deformation characteristics of sand-gravel mixtures. Tested soil was a mixture of Babolsar sand from the shores of the Caspian Sea and Karaj River gravel. Portland cement was used as the cementing agent and fibers 12mm in length and 0.023mm in diameter at 0%, 0.5% and 1.0% were added to the mixtures. Triaxial tests were performed on saturated samples in consolidated drained and undrained conditions at confining pressures of 100, 200 and 300 kPa. Deviatoric stress-axial strain, volumetric strain-axial strain, pore pressure-axial strain curves with deformation and stiffness characteristics were investigated. Tests results show that fiber addition increased peak and residual shear strength of the soil. Fiber addition resulted in an increase of the maximum positive and negative volumetric strains. In undrained condition, fiber inclusion caused increase in initial positive pore pressure and final suction. It has also been observed that fibers decreased initial tangent stiffness of the cemented sand-gravel mixture.
Dr. Ehsan Pegah,
Volume 17, Issue 1 (3-2023)
Abstract
The ratios of elastic shear stiffness anisotropy and fabric anisotropy in granular soils are of very important characteristics in soil mechanics, which can influence directly lots of geotechnical engineering attributes. The shear stiffness anisotropy in a soil mass is directly related to the soil fabric anisotropy, which in turn has a fundamental contribution in variations model of shear stiffness anisotropy ratio. The main objective of this study is to evaluate the variations ranges of shear stiffness and fabric anisotropy ratios in granular soils by developing a novel approach for estimating fabric anisotropy ratio from soil grading and particles shape properties. By presuming cross-anisotropy, the anisotropic shear stiffness values of 1042 conducted tests on 200 distinct sandy and gravelly soil specimens from 43 various soil types of diverse sites throughout the world were acquired from literature. Those were then integrated with their associated void ratios, stress conditions, grading parameters and particles shape specifications to produce a comprehensive database of anisotropic shear moduli with respect to testing conditions. The collected data were analyzed, from which the shear stiffness and fabric anisotropy ratios could be calculated for examined geomaterials. The resulting values for fabric anisotropy ratio were then depicted versus grading and particles shape information to inspect the level of dependences through deriving the respective correlations. The findings of this study may serve as a suitable technique to obtain first-order approximations for fabric and shear stiffness anisotropies from soil grading and particles shape characteristics.
