Investigation of the Effect of Silt Content on the Dynamic Properties (Shear Modulus an‎d Damping Ratio) of Chabahar Carbonate San‎d

10/22/2026 12:00:00 AM

This experimental study investigates the dynamic behavior of carbonate san‎ds, silts, an‎d their mixtures from the Makran region. Using resonant column an‎d cyclic triaxial tests, soil response was eva‎luated across a wide range of shear strains. The results demonstrate significant deviations in the dynamic characteristics of Makran carbonate soils from conventional silicate soils. Increased confining pressure an‎d relative density were found to enhance stiffness properties, yielding a higher maximum shear modulus an‎d reduced damping ratio in san‎d-silt mixtures. However, this improvement coincided with more brittle behavior, characterized by steeper degradation of the normalized shear modulus an‎d accelerated increase in damping. The normalized shear modulus degradation in carbonate mixtures showed greater sensitivity to void ratio changes compared to silicate soils. This sensitivity progressively diminished with increasing silt content, becoming virtually negligible in pure silt samples where the normalized shear modulus remained largely independent of void ratio variations The results within the small-strain range indicate that an increase in silt content up to the 30% threshold leads to a decrease in the shear modulus an‎d threshold strain, an‎d an increase in the damping ratio. Furthermore, the slope of the decay in the normalized shear modulus curves an‎d the curve for the increase in the damping ratio becomes gentler. However, beyond this threshold (30% silt), with a further increase in silt content, the shear modulus continues to decrease. In contrast, the trends for the threshold strain an‎d the damping ratio reverse an‎d become decreasing. In this range, the slope of the decay in the normalized modulus curve an‎d the slope of the increase in the damping ratio become steeper. A predictive model developed for maximum shear modulus demonstrated high accuracy (error < 6%) with linear relationships between model coefficients an‎d silt content. This study underscores the necessity for developing specific design criteria for carbonate san‎d-silt mixtures, accounting for their fundamentally unique dynamic behavior compared to silicate soils.

ماسه كربناته , مدول برشي , مدول برشي بيشينه , نسبت ميرايي , مكران

Carbonate sand , Shear modulus , Maximum shear modulus , Damping ratio , Makran

Hamidreza Hamrang

Aliakbar Heshmati, Hossein Salehzadeh