3D Laser Scanning for Tracking Supported Excavation Construction

The increase in urbanization, population density and traffic congestion in major metropolitan centers around the world has led to greater demand for underground space. Development of underground space in a timely and cost effective manner while maintaining a safe environment onsite and in the surrounding areas poses tremendous challenges. Open cuts and tunnels have long been used to create underground space, but with the increasing usage of underground space, new constraints on the design and construction of such projects are added. One of the major concerns when constructing underground space is the impact of ground movements related to construction activities. These ground movements can be critical to adjacent sensitive buildings and utilities. Hence, it is very important to predict and control the magnitude and distribution of ground movements, which result from building underground space. Significant progress has been made in the development of automated systems to monitor ground deformations due to excavation activities. However, often enough there is a lack of similar records for the construction activities and excavation geometry. Without information about the corresponding excavation configuration, data on ground deformations will be of very limited use. The engineer will be unable to correlate the movements to the corresponding excavation stage. This paper introduces the use of a promising technology, 3D laser scanning, to significantly enhance collection of as-built data to monitor construction progress for deep supported urban excavations. The paper presents experiences on a recent project currently underway in the Chicago area. It summarizes the processes of conducting 3D laser scanning in the field, along with the lessons learned from the field trials.