Influence of consolidation properties on the cyclic re-liquefaction potential of sands

The relative density can be used as the main indicator to assess the liquefaction resistance of clean sands. As relative density of the sand deposit increases significantly following the initial liquefaction, one should expect that the soil can improve its liquefaction resistance. However, earthquake records indicate that densified sand can be liquefied again (re-liquefied) at smaller cycles by the similar seismic loadings. This work aims to clarify the counterintuitive finding that, after the first liquefaction, the resulting significant increase in relative density (induced by settlements and variation of the water level) do not necessarily imply an increase in the number of loading cycles for re-liquefaction. In this paper, we present a series of experimental results concerning the cyclic liquefaction and the following re-liquefaction of clean sand deposits. The experimental setup is performed by a shaking table, transmitting one-degree of freedom transversal motion to the soil within the 1.5 m high laminar shear box. At four different seismic demands, the input excitation was imposed three times to examine the influence of the initial distributions of the relative density and the consolidation characteristics on the liquefaction potential of the sand. The re-liquefaction cycles of the sand, which previously experienced liquefaction under the same seismic loadings, show that post-liquefaction reconsolidation of the sand deposits affects the re-liquefaction resistance.