Near-fault velocity pulse effects on earthquake response of a dry sand site: Centrifuge modeling

Near-fault (NF) velocity pulses exhibit more damaging effects on structural performance, while their impacts on the seismic response of sand deposits remain unresolved. A centrifuge shaking table test was conducted on a stratified sand deposit consisting of: (1) a 12.5-m fine sand layer with 50 % relative density, and (2) an underlying 15.0-m coarse sand layer with 80 % relative density, forming a 27.5-m total soil column. A representative pulse-type acceleration time history was selected and processed using the Baker algorithm to extract out velocity pulse components. The selected original pulse-type record and the resulting residual non-pulse-like acceleration motion were employed as the shaking table inputs to investigate NF velocity pulse impacts on the seismic response of the dry sand deposit. The experimental results demonstrate that the centrifuge shaking table can effectively reproduce the primary characteristics of seismic pulses. The near-fault velocity pulses in ground motions enhance site amplification effects, generating greater shear stresses and shear strains, and consequently leading to permanent surface settlement. The above conclusions are derived solely from a ‌single typical pulse-like ground motion record, and thus require further validation‌ through more ‌physical model testing and numerical simulations.