Double Casing Helps Keep BART Tunnel Structures Safe and Operational

摘要

Each year, approximately 126 million trips are made on the Bay Area Rapid Transit (BART) system, which has served the San Francisco Bay area since 1972. To keep its tunnel structures safe and operational, BART has established certain guidelines for new construction within its proximity. One of the guidelines requires that permanent building loads be transferred below the BART "zone of influence" (ZOI) or "no-load zone," defined as the area above a line from the bottom of the tunnel at a slope of 1.5H:1V to the foundation element.