Comparative study of shear strength characteristics of dry cohesionless sands from triaxial, plane-strain and direct shear tests

ABSTRACT

Knowledge of strength properties and deformational behaviour of soils under different loading conditions is necessary in the analysis of most of the geotechnical engineering problems. This paper presents a comparative study of shear strength characteristics of sands as obtained from triaxial, plane-strain and direct shear test results. The experimental results on shear strength characteristics of dry sands obtained from triaxial, plane-strain and direct shear tests, were analyzed in order to investigate the effect of soil relative density or soil porosity on the angle of shearing resistance, dilatancy factor, particles interlocking, and volumetric strain and axial strain at failure. Furthermore, the results were used to develop correlations connecting between the angle of shearing resistance of triaxial condition test and the direct shear test, and between the angle of shearing resistance of plane-strain and triaxial compression conditions. The correlations developed take into account the interaction between soil relative density, dilatancy factor and particles interlocking. Good agreement has been obtained between the predicted results values using the proposed methods and the results of the present experimental investigation and those available in the literature

KEYWORDS:

• Shear strength
• triaxial
• plane-strain
• direct shear
• prediction
• comparison

NOTATION

${\bar{A}}_i,\overline{B_i,}\overline{C_i}and{\bar{D}}_i$ are coefficients, which depend mainly on D and OCR

D:	=	the dilatancy factor
Dx:	=	the diameter of the sand particles for which (X)% of particles are finer
dε1:	=	plastic component of the axial strain
dv:	=	plastic component of the volumetric strain
Gs:	=
K:	=	the material parameter;
ko:	=	coefficient of earth pressure at rest
OCR:	=	overconsolidated ratio
e:	=	the initial void ratio of the sand.
emax.:	=	maximum void ratio of sand
emin.:	=	minimum void ratio of the sand
R:	=	the principal stress ratio
Rd:	=	the relative porosity of the sand
Rps:	=	plane-strain principal stress ratio
RT:	=	triaxial principal stress ratio
Si:	=	sand ‘i’
β:	=	the angle of dilatancy
Δy:	=	Change of thickness at failure
φcv:	=	the angle of shear resistance at constant volume
φps:	=	angle of shearing resistance of plane-strain test,
φT:	=	angle of shearing resistance of triaxial test,
σ1:	=	major principal stress,
σ3:	=	minor principal stress
σ:	=	Normal stress applied on the plane of failure
τ:	=	shear stress on the plane of failure

Acknowledgments

The financial support from the Natural Science and Engineering Research Council of Canada (NSERC) and Concordia University are acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.