Study on the Method of Filling Pit Foundation Treatment in Beijing Area

The original site was a sand and gravel pit, which was partially backfilled at a later stage. In order to accommodate urban development, engineering construction was undertaken in the sand and gravel pit. However, due to inadequate consolidation, collapsibility, non-uniformity, low bearing capacity, and significant deformation of the fill soil, soil filling foundation treatment was deemed necessary. For a specific project, based on the geotechnical engineering investigation report and subsequent foundation treatment design, the author employed FLAC3D numerical analysis to assess the effectiveness of dynamic compaction combined with CFG (cement flyash gravel) pile composite foundation. This analysis was conducted considering the foundation pressure specified by the design. Based on the numerical analysis, different foundation treatment designs were implemented for various buildings. Subsequently, standard penetration tests and load tests were conducted upon completion of the foundation treatment. The test results demonstrated that the treated foundation’s bearing capacity met the design requirements. Furthermore, settlement observations indicated that the buildings experienced settlements ranging from 12.00 to 36.40 mm, which aligns with the design value of 50 mm.