Stress-Dilatancy for Soils. Part III: Experimental Validation for the Biaxial Condition

Abstract

Abstract:The validation of the general stress-dilatancy relationship is shown based on biaxial compression test data presented in the literature under drained and undrained conditions. Rowe's and Bolton's relationships can be treated as simplified forms of the general stress-dilatancy relationship. The stress ratio values are a function of not only the dilatancy but also the intermediate principal stress, the non-coaxiality angle defined by Gutierrez and Ishihara and the stress-strain path. For many granular soils, the critical frictional state angle of the shearing resistance  o = υ c Φ and parameters  and  are functions of the drainage condition, the stress level and the stress and strain paths.

Direct Shear Test for Coarse Granular Soil

“…Note that using a different approximation method may produce slightly different values of these parameters [17,18]. Using the small size box for direct shear, identical prepeak and post-peak relationships between τ/σ n and δh/δs were obtained and α = 0, β = 1.4 [16]. This proves that higher non-homogeneity deformation in the shear band is in the large box apparatus, compared with the small one.…”

“…where Φ° is the critical frictional state angle, and α and β are the parameters of frictional state theory. For direct shear, as a special case of plane strain conditions (biaxial compression), the Lode angle for stress may be assumed to be θ = 15° [11,16], h is the growth of sample height during shear, and s is the displacement of the lower part of the shear box. An example of the stress-dilatancy relationship is shown in Fig.…”

“…For the tested coarse granular soil, Φ°= 41.2°. The parameters α and β represent the mode of deformation [11,16] and the level of soil destructuration in the shear band. For almost all tests, at the initial phase of shearing, the relationship between τ/σ n and δh/δs was not linear and parameters α and β cannot be accurately calculated.…”

Stress-Dilatancy for Soils. Part IV: Experimental Validation for Simple Shear Conditions

“…The simple shear condition is treated as a special case of the plane strain condition [33]. Because the stress and strain during shear are unknown in the conventional simple shear test, additional assumptions are introduced.…”

Rate effect on the shear resistance of sandy clay in direct shear tests

“…Almost in all tests the point at which stress ratio significantly changes was observed. Therefore, the Frictional State Theory (Szypcio, 2016(Szypcio, , 2017a used for the analysis gave new possibilities of direct shear tests results interpretation.…”