Abstract:
Geotechnical engineering projects in confined urban environments present a unique array of complexities and challenges. These projects often involve working in close proximity to neighboring buildings, historic landmarks, subway tunnels, bridges, utilities, and other critical infrastructure. Additional layers of complexity arise from the need to coordinate with community boards, public agencies, and building owners whose requirements and concerns must be balanced with the technical, logistical, and cost demands of the project. This paper reviews lessons learned and best practices from several challenging geotechnical projects in dense urban settings and will highlight the challenges, successes, and look back on what could have been done differently knowing what we know now. This will include emphasizing the importance of stakeholder engagement, meticulous planning, and adaptive problem-solving.
Projects examples will discuss (1) encountering historical sheeting installed “over the property line†on a zero lot line construction project requiring modification and redesign of the proposed shoring system, (2) design and installation of an enabling shoring system for slurry wall installation including support of utilities, sensitive historical structures, transit lines, and removal of thick reinforced concrete slabs supported by timber piles from a previous building on the site, (3) enabling support of excavation required to remove an existing 100 plus year old granite block wall, establishment of movement criteria for bridge piers adjacent to the granite block wall, and mitigation measures used during construction to reduce movements of the bridge piers, (4) movement of adjacent buildings due to enabling and slurry wall installation prior mass excavation and mitigative measures taken during construction to reduce future adjacent building movements (5) removal of existing concrete caissons to enable sheeting installation against an existing brick building, construction dewatering mishaps, and building movement during excavation along with mitigation measures employed, and (6) movement associated with the installation of a solider pile and lagging system with tiebacks adjacent to and below a concrete retaining wall.
These project examples will provide food for thought for future work in confined urban environments to achieve successful projects by taking into consideration stakeholders concerns, meticulous planning and design, construction means and methods, and adaptive problem-solving.