Rigid and Flexible Bracing Systems on Adjacent Sites

Design, construction, and performance case histories are presented for rigid and flexible bracing systems supporting 45 ft deep basement excavations in soft soil (San Francisco bay mud). The rigid bracing system was a soldier-pile tremie-concrete wall braced with tiebacks and inclined rakers. The flexible bracing system was a sheet-pile wall supported by diagonal struts and inclined rakers. The slurry wall system, designed in accordance with conservative pressure criteria, limited adjacent ground movements to small magnitudes; pavements and utilities were undamaged. The sheet pile bracing system, designed in accordance with less conservative criteria, experienced moderately large deformations that caused minor to moderate damage to pavements, sidewalks, and buried utilities.