Densification is commonly used under shallow foundations to improve their performance during earthquake loading in liquefiable deposits. Centrifuge tests of level ground deposits of sand with different relative densities under seismic loading confirm that densification considerably reduces the settlement of the improved ground, although it can still be relatively large (155 mm in real scale). On the other hand, densification seems to increase the dynamic loading transmitted to the structure and does not prevent considerable loss of soil stiffness, as soon as the cyclic loading is strong enough. Since the influence of the structure on the ground initial stress state and the dynamic behaviour of the soil-foundation system is expected to be important, future research is expected to include a foundation in the tests. This future research should clarify the potential benefits and drawbacks of densification, especially on the likely adverse effects of observed large acceleration spikes on shallow foundations.
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