Adopting Underslab Drainage System to Tackle Groundwater Uplift Force: A Holistic Overview and Experience Consolidation

Groundwater uplift is one of the key factors affecting the foundation design of building works, especially for deep basements with limited building self-weight. In Hong Kong, it is common to use tension piles to resist groundwater uplift for building projects or provide additional counterweight to overcome the uplift with adequate safety factor. However, tension pile can be costly, which renders the initiatives to devise a more cost-effective and sustainable alternative. This paper presents a comprehensive review of the novel strategies for uplift control, aiming for producing a more economic foundation solution through a synthesis of theoretical frameworks, case studies, and practical experiences. The review focuses on the application of underslab drainage system beneath the basement slab in Hong Kong. The design principles of the system, the construction control and considerations, and the routine maintenance are discussed. Through a meticulous consolidation of experiences, the paper showcases a few successful applications of underslab drainage system from design prediction, through site verification and finally to implementation stage. In one of the case examples, prolonged groundwater monitoring has been carried out to demonstrate the reliability and the effectiveness of the system.