Foundation design of cryogenic tanks in Taiwan: Settlement computation by classic geotechnical and by Plaxis FEM method compared to the measurements obtained during hydrotests

Since 1995, a huge petrochemical plant is under construction on a 24 km² artificial reclaimed island on the West coast of Taiwan. Foundation design is governed by the poor geomechanical characteristics of the hydraulic backfill and of the alluvium soft soil.

Due to high seismic level of the region, the cryogenic tanks have been founded on shallow raft without piles. To avoid liquefaction risk and to decrease the settlements, the soil has been, in a first step, improved by dynamic compaction. Nevertheless cryogenic tanks must follow very strict settlement criteria provided by international standards. Additional soil improvement using stone columns has been therefore requested before the raft foundation construction.

The settlements of flexible raft have been computed by classic geotechnical method. The results of this computation have then been introduced in a Plaxis model to calibrate the soil data. In a last step, the rigidity of the structure has been applied to compute the final raft deformations.

After tanks erection, settlements of the tank raft have been measured during hydrotests. The measured values of the deformation are consistent with the computed values.