Effect of loading conditions and stress history on cyclic behavior of Kutch soil

Abstract

Cyclic behavior of cohesionless soils at cyclic strains and frequencies resembling strong ground motion is highly non-linear. Recent developments in numerical analysis tools for the non-linear dynamic response of soils necessitate the determination of soil properties at different cyclic deformations. In this study, liquefaction characteristics and dynamic properties of medium dense silty-sand at different cyclic loading conditions (frequency and amplitude) and various overconsolidated states are investigated. The soil was collected from Fatehgarh dam, located in high seismicity Kutch region of Gujarat (India). At given strain amplitude, increased cyclic shear strength response was observed at higher loading frequencies during the 1st cycle; after that, the strength was essentially similar at all the frequencies. However, at a given frequency, liquefaction resistance decreased with increasing amplitude. The stress history had a strong influence on the cyclic response of soil the soil. The findings revealed a significant increase in cyclic shear strength and a decrease in pore water pressure leading to increased liquefaction resistance at higher overconsolidation ratios. The gain in cyclic strength was observed to follow a power law relationship with the degree of overconsolidation. Heavily overconsolidated states displayed improved soil behavior exhibiting higher shear modulus, higher degradation index, and lower damping ratio.