Presidio Parkway Project Phase 1

摘要

The project is located in the 200 year-old Presidio, a National Park, in San Francisco, California. An integrated team consisting of Caltrans Geotechnical Services and the joint venture (JV) of Arup and Parsons Brinckerhoff provided geotechnical engineering services. Originally constructed in 1936, the existing Doyle Drive needs design, seismic and traffic safety improvements. The project faces several significant challenges: highly variable and poor geologic conditions in a highly active seismic setting, preserving the natural and historical Presidio resources, providing extensive public outreach and inter-agency coordination for a large group of stakeholders and removing and replacing the existing facility while maintaining traffic during construction. The many innovative ideas utilized in this project include: an integrated team of Caltrans drilling crews and local drilling subcontractors used for the subsurface exploration, a foundation contractor feedback meeting held for the Southbound Presidio Viaduct Bridge, a bridge foundation system design that includes a 12 foot diameter steel casing over a rock socket, a Cement Deep Soil Mixing and Cast in Drilled Hole Test Project, using separate excavation pay items for the different ground conditions, a special subdrain that maintains groundwater flow to the wetlands below a bluff while meeting the project needs of draining a tunnel, a soldier pile tangent beam retaining wall with steeply inclined heavy duty tiebacks used to avoid instability to adjacent facilities, and a lightweight fill combined with a retaining wall used for a temporary detour over soft soils in order to maintain traffic during the 3 to 4 year construction period.