Pipe Jacking in a Complex Urban Environment - Boston, Massachusetts

A 224m (735-ft) long segment of steel casing was successfully installed using conventional pipe jacking methods in complex ground conditions located in a highly congested section of downtown Boston. The 1370mm (54-in.) outside diameter permalock steel casing, was installed in two reaches with lengths of 133m (435 ft) and 91m (300 ft) located at depths of 10.7m (35 ft) and 7.6m (25 ft), respectively. Ground conditions ranged from hard clayey soils with boulders to fine sand to sand and gravel below the water table to silt to stiff clay. The installation passed beneath both an active transit station and numerous near surface utilities. This paper will present the successful installation of the steel casing and include a discussion of the many challenges faced during construction. Challenges included siting of jacking and receiving pits, running ground that was stabilized by chemical grouting, unanticipated ground and coordination with various City Agencies. All construction activity was conducted at night and required that this critical thoroughfare be open to all stakeholders during daylight hours.