Abstract: This paper presents a case history of a deep excavation secondary excavation supporting system design and monitoring in Haizhu District, Guangzhou City. The original excavation support structure design, adjacent environment, excavation depth, and subsurface conditions are introduced, and the secondary supporting system design options are also presented. The reinforcement design option adopted is as follows: high-pressure jet grout + cast-in-place reinforced concrete piles (already installed and accepted by the construction inspection) + prestressed ground anchors (secondary improvement installations). The correspondent excavation monitoring system are also designed and the excavation process as well as the adjacent structures are monitored. The results show that: 1) the horizontal displacement of the soldier pile top and the vertical cumulative horizontal displacement increase with the excavation depth, but within the  allowable range defined by the design and specification; 2) the surface settlement of the edge excavation is firstly increasing and then decreasing and finally tends to a stable state; 3) the soldier pile and ground anchor support secondary reinforcement program is more reasonable, and the results of the study can provide a reference for the subsequent design and construction similar projects.

Key words: Deep Excavation, Soldier Pile and Ground Anchor Support, Secondary Improvement, Construction Monitoring, Displacement