Key Techniques and Applications of Underground Space Development and Functional Upgrading for Heritage Buildings on Soft Soil Foundations

The Red Mansion at No. 106 Huangpu Road， Shanghai， was constructed in 1911. It is a three-story brick-wood structure. In its comprehensive protective renovation project， three major challenges were encountered： the simultaneous construction of a complex group of adjacent deep foundation pits， the overall ultra-high jacking by 6.55 m to restore its historical appearance， and the synchronous development of underground space together with the improvement of the building’s seismic performance. To address these challenges， a complete set of key techniques was proposed， integrating underpinning， active deformation control， synchronous high-position jacking， and seismic isolation with story addition. Using an adjustable active underpinning system， the cumulative additional deformation of the Red Mansion during the construction of the surrounding deep foundation pits was controlled within ±5 mm. A relay lifting technique combining "lifting + jacking" was adopted to achieve the ultra-high jacking of 6.55 m， along with the simultaneous high-position rectification of 300 mm. The addition of a seismic isolation layer significantly enhanced the structural seismic performance. After three rounds of whole-process load transfer， the maximum inclination ratio of the building foundation was reduced from the initial 9.12‰ to below 2.5‰， with no new structural cracks generated. This project realized the in-situ preservation， jacking with story addition， and functional upgrading of an outstanding historical building in Shanghai under the condition of simultaneous construction adjacent to a group of deep foundation pits， setting a record for the highest overall jacking height of modern outstanding historical buildings in China.