Field Measurements on Piled Rafts with Grid-Form Deep Mixing Walls on Soft Ground

Abstract

Piled raft foundations have been used for many buildings including tall buildings in excess of 150 m in height in Japan, since a piled raft was first used to the four-story building in 1987. This paper offers recent two case histories for an advanced type of piled rafts. The piled rafts combined with grid-form deep cement mixing walls were employed for a seven-story building and a twelve-story building to cope with liquefiable loose sand as well as to reduce consolidation settlements of soft cohesive soil below the loose sand. The high-modulus grid-form soil-cement walls confine the liquefiable loose sand so as not to cause excessive shear deformation to the loose sand during earthquakes. To confirm the foundation design, field measurements were performed on the foundation settlements and load sharing between raft and piles from the beginning of construction to 72 and 27 months after the end of construction for the former and the latter buildings.