Potrero Hill Slide and Correction

With the completion of construction of a 60-ft highway cut and a rock bolted retaining wall in the Potrero Hill area of San Francisco, surface and subsurface movements of sufficient magnitude to cause minor building and foundation damage were observed directly above and adjacent to the wall. Accompanying movements in an unreinforced masonry railroad tunnel 30 ft below the base of the wall indicated the need for immediate correction in order to forestall serious distress to a major passenger and freight facility. The corrective treatment selected was a system of 30 individual reinforced concrete portals or bents around and over the tunnel. Design of this system was based upon a finite element analysis. During construction, six of the portals were instrumented with SR-4 and vibrating wire type strain gages. The stresses and strains indicated by the portal instrumentation revealed reasonably good agreement with those predicted by the finite element analysis.