Strain-dependent dynamic properties of Bushehr siliceous-carbonate sand: Experimental and comparative study

Mixtures of calcareous and siliceous sediments are found in extensive areas of the earth including the seismic-prone regions. However, a few experimental studies on dynamic properties of such soils have been conducted, compared with the siliceous soils. The investigations presented in this paper include: (1) experimental study on shear modulus (G) and damping ratio (D) of Bushehr siliceous-carbonate sand under various stress-density states, (2) comparison of the results with the available models of siliceous sands, and (3) development of a modified-hyperbolic model for the studied siliceous-carbonate sand. Cyclic triaxial and resonant column tests were conducted on reconstituted samples of the Bushehr sands, retrieved from the northern coast of the Persian Gulf. The results indicate that dynamic properties of the sand are less affected by the initial stress anisotropy compared with the initial mean confining pressure (σ'm) and relative density (Dr). The effect of Dr and stress anisotropy on the shear modulus is more pronounced in higher values of σ'm. Noticeable discrepancy has been observed between the experimental results of the Bushehr siliceous-carbonate sand and the previous models basically developed for the siliceous sands. Modified hyperbolic models are presented as the shear modulus and damping curves (i.e., G/Gmax-γ and D-γ) of the tested sand. The hyperbolic models presented in this study can be used for site response analysis of the regions with similar siliceous-carbonate deposits.