Lessons learned in ELS design and construction

Synopsis

In Dec 2023, Geotechnical Engineering Office issued GEOPublication No. 1/2023 – Deep Excavation Design and Construction. It documented the experience gained, and advances in design and construction of deep excavations in Hong Kong since the publication of GCO 1/90. Recommendations given aim to achieve economic excavation and lateral support (ELS) works design, construction time saving, and ground deformation monitoring and control enhancements.

The ELS design for an ongoing project at Kwai Chung implementing the recommendations of GEO Publication No. 1/2023 was recently approved by the Buildings Department. This talk will present experience gained in the approval progress and cover two major aspects in the design: the revamped 5A monitoring scheme, and the design assumptions of ground water levels (GWL). Compared with the traditional 3A monitoring scheme with maximum 25mm settlement limit, the proposed 5A monitoring scheme on trigger level determination is more rational with excavation depth considered. Specific…