Geotechnical Evaluation of California Hospital Sites


Slate Geotechnical Consultants has conducted geologic and geotechnical evaluations of more than twenty existing structures at more than 10 hospital campuses across California for HCAI (formerly OSHPD) Structural Performance Category-4D regulation. For each campus, Slate reviewed the existing subsurface information to characterize the site and subsurface conditions; assessed the potential for earthquake-induced geologic hazards (e.g., surface fault rupture, landsliding, liquefaction and related phenomena, and tsunami inundation); and developed geotechnical recommendations for the structural analysis of existing shallow and deep foundations. Response spectra were developed in accordance with the governing building code at the time of the project, for some sites the final response spectra include consideration of kinematic effects. Select sites required the development of scaled time history records for use in nonlinear structural analyses. Where buildings are supported by deep foundations, Slate provided an assessment of axial, uplift, and lateral capacities, including group effects where appropriate. Slate also developed geotechnical recommendations for proposed retrofit foundation elements and retaining walls.

To date, Slate has evaluated and provided recommendations for buildings ranging from single-story reinforced concrete structures founded on shallow footings, to steel moment frame towers with more than 10 stories that are founded below grade on deep foundations. Deep foundation pile types vary from drilled shafts to belled caissons to Raymond piles. Analysis methodologies were tailored to the complexity of the building and needs of our clients, from linear-elastic, perfectly plastic analysis for shallow footings to nonlinear-cyclic finite-element analysis for deep drilled shafts.

Slate has worked closely with the structural engineering team throughout the project to develop appropriate criteria given complex foundation configurations, subsurface conditions, and seismic settings. Reports documenting the evaluation at each site are submitted to HCAI and the California Geological Survey for review, as required by SPC-4D regulation.