Liquefaction potential of horizontal layers in successive earthquakes

It is believed that successive earthquakes result in densification of the soil layer decreasing the liquefaction risk. While there is some evidence on re-liquefaction potential of sandy layers in successive earthquakes, very little experimental data exists. In order to investigate this aspect further a series of centrifuge tests was conducted using fine silica sand which is susceptible to liquefaction due to its grain-size distribution. The centrifuge tests were performed at 50g in the ESB model container with accelerations and pore pressures monitored during each test when the sinusoidal ground shaking was applied. This paper presents the results of dynamic centrifuge tests on saturated horizontal sand layers to show the changes between soil layers with different relative densities and during successive earthquakes. It will be shown that with successive earthquakes the loose sand layers densify and are less susceptible to liquefaction. The strength of soil with liquefaction or partial liquefaction varies and therefore it is important to distinguish this in geotechnical design.