Excavation-Induced Movement of Adjacent Foundations-Paper

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The paper analyzes excavation-induced vertical movements of adjacent foundations using data from 21 deep excavations in Boston and Cambridge. The excavations, 20–75 ft deep and supported by concrete diaphragm walls, were built using conventional or top-down methods. Nearly 1,000 survey points on 98 neighboring structures were monitored. The study compares movements by foundation type and against the empirical limits proposed by Clough and O’Rourke (1990).<br /><br />Most observed movements fell within the earlier limits for stiff to very hard clay, but many exceeded them. The authors attribute this partly to Greater Boston’s often softer soils, where basal heave and other global ground movements can extend an excavation’s influence farther than conventional 1:1 or 2:1 influence zones suggest. They propose broader movement envelopes for the region.<br /><br />Top-down construction generally produced smaller movements of adjacent shallow foundations than conventional construction. For deep foundations, construction method had less apparent influence. Most deep-foundation movements were within the Clough and O’Rourke limits, except for some caissons that settled substantially when tiebacks were installed beneath them. Structures supported by piles extending into glacial soils or rock, and by rock-founded slurry walls or load-bearing elements, showed negligible movement.<br /><br />The findings emphasize that movement predictions should account for local soil conditions, foundation type and depth, construction methods, and potential global soil response—not only wall movement. Historical project data and empirical relationships can support design estimates and help guide decisions during construction.

Keywords

deep excavations

adjacent foundations

excavation-induced movement

Boston and Cambridge

diaphragm walls

top-down construction

foundation settlement

basal heave

Clough and O'Rourke limits

survey monitoring