Improving planning in congested sites using 3D and 4D modelling: A case study of a pile-supported excavation project in Chile

IT use in construction has grown lately and it has helped project teams to better understand and improve sizing of work packages. This supports decision making when selecting construction strategies, which is one of the main problems associated to projects late completion and cost overruns. Large excavation projects can benefit from the use of 3D and 4D models to improve efficiency of construction processes. In this study we wanted to demonstrate how the use of these technologies in the planning stage helps in the reduction of the project schedule and resource use. We developed a 3D model for a discontinuous pilesupported excavation project (56,000 m3; 18 m deep; 89 piles with up to three anchor levels). Then, we prepared two 4D models: one used to show the asbuilt excavation, while the other showed an improved process. The improved process included considerations such as the level of detail for the 3D model geometry, placement of key design elements (e.g., excavation access ramp); analysis of excavation strategies; etc. Both 4D models were compared to check schedule reduction (and indirectly resource use). To validate the 4D modelling of civil works, the project team was interviewed and surveyed regarding both 4D models. Results showed that 4D models used in excavation processes help the project team to better plan and select construction strategies due to a better understanding and sizing of the excavation work. The result is an improved process which is shorter, and more resource efficient than the base case (as-built model).