Discussion of Foundation Design of High-rise Building on Old River Bed

摘要

The paper presents the foundation design of a high-rise building on old river bed. As the geological structure of half of the site is soil and half is rock, it is difficult to design the foundation of the building. No high-rise building example has been found on such soils with completely different mechanics performance. Based on lots of site investigation, research and calculation, the combination of pile supporting box foundation is designed as the foundation type. "Short" rock-socket piles and "long" piles enveloped in soil are laid out in the site on much comparison. Full-scale load tests including 3 excavating-hole piles are made to get piles bearing capacity before construction. Tests indicate the piles bearing capacity is 4000kN. Box foundation can adjust the uneven ettlement effectively with its magnitude stiffness and totality. During the intercourse with piles, box foundation works as a cantilever beam. In light of China criteria of foundation design, piles and box foundation are designed with some detailing measurements and integrality. In addition, some strengthening measurements, 135 CFG short piles being added along 4 long horizontal axis, were made to improve foundation soil bearing capacity. In order to strengthen rigidity of upper structure, the cast-in-place slabs beside the boundary are thickened to 150mm. And slabs bar run through slabs as possible as it can. Additionally, latish-cast belt are laid every layer from foundation plate to top of the building. The foundation settlements surveys are taken from beginning construction until the building is in use for 2 years. The foundation settlements survey results indicate that the foundation scheme is feasible and successful.