Abstract: A deep excavation supporting in the soft peaty cohesive soils for the metro project in Shaoxing has the characteristics of poor geotechnical subsurface conditions and complex surrounding environments. The informative monitoring system was established during the process of the excavation. The lateral deflection of the supporting structure, axial loads in the strut structure and ground subsidence data are collected and evaluated. The results show that: 1) a relatively large lateral deformation within the supporting structure was observed. Especially, an obvious lateral deflection in the supporting structure occurred when the last excavation at the bottom was observed; the spatial effect at the corners of the excavation controlled the lateral deflection. 2) The deformation characteristics of the supporting structure in different parts of the deep excavation in the soft peaty cohesive soils are obviously different under the joint action of eccentric pressure from adjacent soils. At the same time, the pressure of the first reinforced concrete beam supports decreases instead of increasing with the increasing depth of excavation, and the axial force in each layer of support on horizontal and vertical planes shows obvious joint movement. 3) The distribution of the surrounding ground subsidence approximates the Perk ground subsidence shape. The value of xmax of the distance between the maximum subsidence point and the edge of excavation retaining structure is 8~13 m (0.5h~0.9h), and the inflection point σ of the curve in Perk formula is 4 m~7 m.

Key words: Soft Peaty Cohesive Soils, Deep Excavation, Deformation Characteristics, Eccentric Pressures