GROUND FREEZING FOR THE EAST SIDE ACCESS NORTHERN BOULEVARD CROSSING- BALANCING SETTLEMENT AND HEAVE CONTROL

摘要

One of the most challenging elements of the MTA Capital Construction Project's East Side Access Project was the Northern Boulevard Crossing which required an SEM tunnel between two 85-ft deep access shafts which extended to as deep as 55 ft below the water table. Tunneling was accomplished beneath a frozen ground arch connecting the two deep excavations, and within very close proximity of the overlying, active subway and elevated transit lines. The work required significant measures to permit installation of freeze pipes and grout pipes through highly variable subsurface conditions below the water table, as well as two critical ground improvement requirements: settlement control and heave control. This paper discusses the pipe installation, the pre-grouting, settlement and heave control, monitoring and instrumentation, and their integration with the overall program.