Hysteresis Behaviour and Energy Dissipation of Niger Delta Soil under Cyclic Loading Conditions

Abstract

The dynamic properties of soils influence seismic site response and liquefaction susceptibility. The previous studies mostly worked on effect of natural fiber and synthetic fiber used in clayey soil to investigate its effect on the dynamic properties of modified soil.This research deepens our understanding of the dynamic behaviour of Niger Delta soils, which is important for evaluating the region's vulnerability to liquefaction and seismic response. By combining experimental data with well-validated empirical models for small to medium-shear strain behaviour in the area's common sandy soils.This study experimentally investigated the behavior of damping ratio and shear modulus under the effects of confining pressure of sandy soils collected from Igbogene Town in the Niger Delta region of Nigeria. Undisturbed samples were acquired from boreholes using thin-walled tubes and consolidated anisotropically under effective stresses of 100, 200, 300, and 400kPa in a cyclic direct simple shear apparatus as per standards. Shear modulus reduction curves were generated from hysteretic stress-strain behavior at shear strains ranging from 0.001% to 2%. The data correlated well with empirical exponential decay models, validating their applicability for Niger Delta region soils. The damping ratio increased nonlinearly with strain, aligning with trends for liquefiable soils. Empirical equations tied the pressure-dependent damping behavior to existing models. Results provided input parameters for seismic ground response analyses. However, wider confining pressure testing would better characterize variability with depth. This work enhances geotechnical seismic hazard evaluations through validated empirical characterizations of small to medium-shear strain behavior for sandy deposits prevalent in the Niger Delta.The findings can be directly used in seismic ground response analysis. These results are expected to improve geotechnical seismic hazard assessments and provide more accurate evaluations of seismic risk in the region.