Shaking table tests on buried pipelines in inhomogeneous soil under longitudinal non-uniform seismic excitation

The seismic response of buried pipelines is primarily affected by the spatial variation characteristics of earthquake motion and the soil inhomogeneity. To investigate the seismic performance of pipelines buried in inhomogeneous soil under longitudinal non-uniform seismic excitation, two multi-point shaking table tests are carried out on model pipelines: one model is buried in homogeneous soil, and the other is buried in inhomogeneous soil. The test results are analyzed and discussed in terms of the strains of the pipelines buried in both homogeneous and inhomogeneous soils under different earthquake intensities, and the influences of longitudinal inhomogeneous sites on the seismic response of the pipelines are studied. The test results indicate that the peak strain of the pipelines in the transient zone where the soil properties change in the inhomogeneous soil model is higher compared with the response in the homogeneous soil model under longitudinal uniform seismic excitation. The maximum strain along the pipeline axis occurs in the transient zone. However, under the longitudinal non-uniform seismic excitation, although the magnitude of the strain peak is decreased compared with the homogeneous soil case at lower loading intensity, similar magnitudes of strain are observed at higher loading intensity, and there is a sharp increase in the strain peaks. Unlike the longitudinal uniform excitation case, the maximum strain peak may appear in the transient zone or soil changed zone due to the combined action of longitudinal non-uniform excitation and inhomogeneous soil. The results may provide insights into the site effects of inhomogeneous soil conditions on the seismic response of buried pipelines.