Proceedings of sessions of Geo-Congress 98, held in Boston, Massachusetts, October 18-21, 1998. Sponsored by the Geo-Institute of ASCE.

This Geotechnical Special Publication contains eight papers discussing the various testing programs undertaken to answer technical questions related to design and construction of the Central Artery/Tunnel (CA/T) in Boston. The CA/T is the largest urban highway construction project in the history of the Interstate system. The magnitude and complexity of the project, set in the variable and difficult subsurface conditions of the 350-year-old city of Boston, have required engineers to develop unique and innovative solutions.

Topics include:

• dewatering and injection testing;
• load testing of deep rock-socketed drilled shafts;
• evaluating various test methods for determining shear strength of marine clay;
• assessing effectiveness of different methods of grouting to prestabilize ground beneath railroad tracks prior to tunnel jacking;
• determining capacity of deeply anchored, tension elements to resist hydrostatic uplift on boat and tunnel structures; and
• evaluating different means for instrumenting old subway tunnels to evaluate impacts of overhead excavation.

Although the tests are specific to the CA/T project, the results have much wider implications for geotechnical design in many other situations.