Liquefaction Mitigation

Stone Columns to prevent soil liquefaction

Soil liquefaction can cause the total loss of shear strength below the foundation of structures.
The well known photo from the Niigata, Japan (1964) earthquake shows buildings that structurally were so sound that even after sinking into the liquefied ground and tilting under an angle of over 45 degrees did hardly develop any cracks in the structure.

No other example could more clearly deliver the message that structural design must closely link to geotechnical design or the overall product is in danger.

The below two sketches show the physics behind the well known positive effect that stone columns have in preventing soil liquefaction during an earthquake.
No other ground improvement system has an as long and well documented track record  in the prevention of soil liquefaction.

Dubai’s Palm Island trilogy (Palm Jumeirah, Palm Jebel Ali, Palm Deira) and the island group named “The World” are a superlative in many liquefaction_3disciplines but they are also the world’s largest lique-faction prevention project. All islands are compacted to strict compaction requirements based on mini-mum required post treatment CPT resistance (example see below) as well as a minimum required subsidence of relevant soil layers during compaction.  

As for embankment settlement simulations, the deformations in-duced by earth-quake shaking can be simulated. The software of choice  for such liquefaction_4liquefaction analysis is FLAC.

The graph on the bottom of this pages shows the deformation of a dike subjected to a 6.0 magnitude earthquake. The deformation of 5 m at the liquefaction_5toe of the dike suggests the need for either a less steep slope (possibly with several berms) or ground improvement to fortify the given geometry.