Reuse of existing bored piles for high-rise building foundation

The Ochanomizu Sola City building1) is one of the largest redevelopments in which existing bored cast-in-place piles have been used in combination with new bored piles for the foundation of a new high-rise building in Japan. The building, completed in 2013, is a 110-m high-rise office building supported by 169 existing bored piles and 99 new bored piles. In addition to the existing piles, the existing foundation slab and pile caps were also reused. During the demolition of the old building, which was constructed in 1983, several types of investigations of the existing piles, including two pile load tests, were conducted to assess their integrity and performance. In the design stage, the safety of the mixed foundation system subjected to vertical and horizontal loads was verified using detailed analytical methods. It was also estimated that approximately 4,000 tons of CO2 were saved by reusing the existing piles. The measured settlements and vertical sharing loads of the existing piles were found to be in reasonable agreement with the predicted results.