Ground Improvement by Compaction Piling

Foundations for Units 1 and 2 of the first large steam power plant in Indonesia consist of concrete rafts supported on slender, end-bearing steelcased concrete piles. Soil investigation established the presence of layers and or lenses of locally loose silty fine sands at various depths. It was necessary to density these materials to ensure that unacceptable differential settlement did not occur between separate shallow foundations and to reduce the potential for liquefaction of the looser zones in the event of seismic disturbance. A design peak horizontal ground acceleration of 0.3 g was calculated and compaction piles used to improve the soil under structures. The principle of compaction piling is to forcefully compact loose soil by introducing significant quantities of additional granular fill throughout the soil mass. This method introduces a far greater quantity of fill material into the soil mass than the sand piling method, which it superficially resembles.