Studying the Impact of Continuous and Multiple Earthquake Ground Motions on Pore Pressure in Saturated Sandy Deposits.

The occurrence of a series of earthquakes of different magnitudes or multiple mainshocks has been reported recently. This leads to the liquefaction of sand due to excess pore pressure generation under undrained loading conditions, which alters the stable structure of the soil to an unstable form. The response of saturated sandy deposits under these conditions is rarely experimented by researchers and the present study highlights this issue. Here six shake table test results are analyzed to understand the initiation of liquefaction in the sand at varying base accelerations (0.15 g, 0.2 g and 0.3 g) at continuous and series of identical shaking events. Multiple shaking events were provided to simulate earthquakes at closely spaced time intervals. The surface settlements and response of excess pore water pressure at various depths within a saturated sand bed due to these shaking events are investigated. The results showed that the soil layer near the surface of the soil is most likely to be liquefied. Also, the re-liquefaction resistance of the sand remains constant for the first few shakings, but the dissipation time of excess pore water pressure decreases with increasing density. [ABSTRACT FROM AUTHOR]