Maximum shear modulus of calcareous sand in Dejebel Dahar, Tunisia and its dependency on applied stress

Abstract

The present experimental investigation aims at investigating the small strain stiffness of calcareous sand as a function of applied stress. The calcareous sand was sampled at Tunisia's Dejebel Dahar region, and the shear wave velocity (Vs) of calcareous sand was measured using modified oedometer cell equipped with bender elements. The results of this study demonstrate that the Vs of the tested calcareous sand is smaller than that of silica sand with minimal crushable particles at relatively low applied stress (σ); however, Vs of calcareous sand is greater than that of silica sand at high σ, reflecting strong dependency of calcareous sand on σ. The applied stress dependency of soils can be expressed as a power function of applied stress (Vs = α (σ / 1 kPa)β, where α = Vs at σ = 1 kPa and β = stress exponent). Generally, the single α-β can capture the dependency of Vs on σ, and the typical β value for sand is around 0.25. The measured β of tested silica sand was around 0.20; while, Tunisia calcareous sand shows β of greater than 0.32, and the dependency of Vs on σ cannot be captured by single α-β. This can be attributed to the fact that the variation of Vs of tested calcareous sand with increasing σ reflects not only fabric change but also particle crushing.

Experimental investigation on dynamic behavior of silt-rich fly ash using cyclic triaxial and bender element tests

“…There exist discrepancies in the threshold strain reported in the past studies below which no change in stiffness has been observed and above which it responds nonlinearly. The threshold strain reported by different researchers is < 10 -3 [101,102], 10 -1 to 10 -2 [103] and 10 -6 [104]. The response analysis of a layered soil system is directly or indirectly dependent on G max , density, excitation frequency, confining pressure, thickness of layer, etc.…”