Construction, Inspection and Lessons Learned for 3.81-m Diameter CIDH Piles – Richmond-San Rafael Bridge Seismic Retrofit-Article

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The Richmond–San Rafael Bridge seismic retrofit included 11 large-diameter cast-in-drilled-hole (CIDH) piles at five pier foundations. Installed between 2002 and 2004 in water up to 21 m deep, the 3.81 m diameter piles had permanent steel casings driven to the highly variable Franciscan bedrock, then 9.15 m rock sockets drilled below the casing. Reinforcing cages and tremie concrete completed the composite foundations.<br /><br />Construction required specialized marine equipment and careful planning to work beneath the bridge’s limited clearance and in strong currents. Contractors used a large barge-mounted crane and hydraulic hammer to install casings, followed by reverse-circulation drilling under polymer slurry. Divers assisted with casing positioning, inspection and repairs. Quality control included slurry testing, socket sounding, concrete-placement monitoring, and nondestructive testing; concrete anomalies in two piles were repaired by hydroblasting and permeation grouting.<br /><br />The main difficulties involved establishing a sound casing seat and stable rock socket. At Pier 38, casing deformation against uneven bedrock obstructed the drill assembly; relocating a stabilizer allowed drilling to finish. At Piers 49 and 48, weak or fractured material around the casing tip caused socket infill. Solutions included redrilling, enlarging and stabilizing the socket with lean or fiber-reinforced concrete, and—in one case—driving the casing deeper.<br /><br />The project’s lessons emphasize detailed planning, purpose-built equipment, coordination among designers, contractors and geotechnical specialists, and close observation during construction. Borings at every pile location were valuable, but bedrock elevation and quality remained uncertain. Drivability studies and monitoring blow counts helped assess casing seating; the authors note that pile-driving analyzer measurements might also have been useful.

Keywords

Richmond-San Rafael Bridge

seismic retrofit

CIDH piles

marine construction

steel casings

Franciscan bedrock

rock sockets

tremie concrete

quality control

pile foundation repair