Boundary effects of a laminar container in centrifuge shaking table tests

Two dynamic centrifuge model tests were performed to simulate dry or saturated sand deposits subjected to 1 Hz base shaking. This experimental study investigated the boundary effects of a laminar container on the seismic response acquired from accelerometers and from pore pressure transducers, both of which were embedded in the sand bed at various depths and distances from the end walls. Under the tested configurations and the employed input motion used in the study, the test results revealed minimal boundary effects on the seismic responses. The measured maximum amplitude, main frequencies, phase lags of acceleration, and the profiles of the calculated RMS acceleration amplification factor were not affected by the boundaries if the instruments were positioned at a distance of more than one-twentieth of the model length from the end walls and were not positioned on the ground surface. No obvious discrepancies were observed in the time histories of excess pore water pressure, measured at a distance of one-fourth of the model length from the end walls. These results infer that variations in the seismic response at the end walls were minimal; hence the laminar container used in the study may be used effectively to simulate 1D shear wave propagation in centrifuge shaking table tests. However, for other testing configurations, a similar study should be undertaken for evaluating the boundary effect of the laminar container on the seismic responses.