However, rapid development and limited urban space in most cities means that deep excavations for underground metro stations are often very close to existing structures such as buildings, surface roads, underground facilities, tunnels and services.
Deep excavations in densely populated urban areas impose specific challenges, especially to the safety of and impact on adjacent structures through potential damage from induced ground and structural movement.
Effective risk management in the design and construction of deep excavations in the urban environment must consider a range of issues:
Deep excavation works in urban areas can also be a nuisance to adjacent property owners and the community with site entry and exit challenges, shoring, underpinning, alterations to operations, dust, noise, vibrations and traffic congestion.
Despite the considerable effort that goes into the design and construction planning and risk management, many urban deep excavation projects encounter problems such as damage to existing structures, interruption of services, delays and cost overruns.
Our experience in the design and construction of underground stations has taught us that a multidisciplinary approach and consideration of all major stakeholders is key to the early identification and resolution of critical issues.
Some innovative solutions that we have adopted to address the specific issues of constructing stations in urban environments include: