Abstract:

With the acceleration of urbanization and continuous expansion of underground space, anti-floating design has become a core issue in ensuring the safety of underground structures. Based on a review of theoretical and experimental methods for the anti-floating performance of underground structures both domestically and internationally, we systematically summarize the research progresses on water buoyancy calculation methods, buoyancy model testing of underground structures, and anti-floating measures for underground structures. We also review the common scientific challenges and technical bottlenecks in current studies on the anti-floating performance of underground structures. The results show that: (1) the selection of anti-floating water levels requires comprehensive consideration of hydrogeological conditions and monitoring data, while there is currently no unified standard for multi-layer groundwater conditions. Anti-floating design for slope buildings is more complex due to significant differences in upstream-downstream water levels. Additionally, seepage significantly impacts buoyancy, particularly the overflow effect of confined water caused by vertical seepage, which can increase buoyancy to more than twice the hydrostatic pressure. Considering seepage effects, nine water buoyancy calculation models for different aquiclude structures were established based on Darcy’s law and seepage equilibrium equations, providing theoretical support for buoyancy calculations under complex geological conditions. (2) Researchers worldwide have derived buoyancy reduction coefficients for specific conditions through theoretical analysis, numerical simulation, and model box testing. Water buoyancy in sandy soils requires no reduction, while in cohesive soils, the reduction coefficient ranges from 0.41 to 0.85. (3) Anti-floating measures for underground structures can be divided into passive and active anti-floating types, with five common measures and their applicable conditions summarized. Passive anti-floating mainly increases the self-weight of the structure or the anchoring force, including methods of anti-floating (uplift) piles and anti-floating anchors (cables). Among these, floating beam capping and counterweight methods are widely used due to their convenient construction and simple operation. Anti-floating piles are suitable for deep excavations but have higher costs, while anti-floating anchors offer economic and flexible solutions but require leakage prevention at connections. Active anti-floating measures reduce water levels through interception and drainage decompression, offering quick results and low cost, though excessive drainage may cause ecological issues and foundation settlement. Practical engineering requires comprehensive consideration of geological conditions, structural characteristics, and cost-effectiveness to achieve balance between safety and efficiency.

Key words: water buoyancy calculation, anti-floating water level, buoyancy reduction coefficient, buoyancy model test, anti-floating measures