Construction Monitoring for the Transbay Transit Center Excavation in San Francisco, California

摘要

Underground space development in large metropolitan areas has become a way to accommodate rapid population growth while sustaining and enhancing the quality of urban lifestyle. A common challenge to urban underground construction is in developing such a space in a heavily built environment with minimal impact on adjacent structures and limited disruption to economic activity. This challenge is exacerbated when soft-to-medium soil conditions are encountered. Hence, urban deep excavations are usually coupled with extensive instrumentation plans and continuous monitoring to evaluate performance and detect deviations from anticipated behavior. The massive Transbay Transit Center (TTC) excavation in San Francisco is a unique excavation of unprecedented scale in soft soils characteristic to the Bay Area. It is approximately 1500 feet long, 85 feet wide and 60 feet deep. Novel technologies were employed to support and enhance the construction control process and monitor ground deformations. This paper will highlight the key features of the field instrumentation program used for the TTC project along with a description of the developed and installed sensors. In addition, it will discuss the data storage and monitoring methods, including the display of construction progress and ground and building movements in a virtual reality environment. The evaluation of ground response to excavation activities will be the subject of future publications.