Stability of steel pile walls and tunnels excavated by shield machines in the urban areas: A case study

Placement of infrastructure and other facilities underground brings superior opportunities for long-term improvements in terms of the environmental impact of urban areas and more efficient use of underground space. However, underground construction in urban areas is a high-risk activity and has been considered a challenging problem for geotechnical and structural designers. Therefore, the evaluation of the stability of underground structures plays a vital role in structural and construction design. This paper presents a case study on analyzing the stability of steel piles walls and tunnels excavated by shield machines in the urban area in Vietnam in terms of the change in internal forces in the structures. The research results show that the excavated stages of the basement influence on the values of internal force in the tunnel lining. In the case of study using composite lining in the tunnel, the thickness of lining concrete 35 cm, steel frame type I-W1000×883 are applied for tunnel excavated before construction of nearby basement, and 30 cm and W1000×350 steel ribs for the opposite side. This research could be applied to evaluate the effects of tunnel excavation near the existing structures in urban such as in the geological conditions in the Ha Noi and Ho Chi Minh City in the near future. However, this analysis also has the disadvantage that it does not consider the construction time as well as the construction sequence of the works during tunnel excavation. The shapes of the tunnel only are circular tunnels and the only type of steel piles in this research. Further study, total evaluation for other types of tunnels and walls of basements should be considered.