Comprehensive treatment of loading and unloading of pile foundation with variable stiffnesses for a high-rise building accident

According to the correct analysis of the reasons for differential settlement of a high-rise building, the integrated reinforcement technologies and measures of the building are established especially. In order to stop the high settlement and inclination ratio and ensure that the deformation of the building meets the standard requirement, the project takes four measures: (1) to unload and reduce settlement at the one side, and to upload and increase settlement at the other side; (2) to take variable stiffness reinforcement by using concrete-filled steel pipe with post-grouting technology; (3) to add the foundation pressure of small-settlement side with post-cast strip cutting method so as to make the settlement be larger; (4) to arrange a scientific and reasonable sequence of construction to realize the expected results. Finally, the settlement ratio of the building decreases from 0.8 mm/d to 0.006 mm/d; the stable tilt value also decreases from 2.8‰ to 2.28‰, which both satisfy the requirements of the national standard. Problems happened during the process of building implementation of the project are also discussed. The research results and strengthening experience may provide reference for similar projects.