Seismic Design Guidelines of Cut-and-Cover Tunnel

The objective of the research project is to develop improved and validated rational guidelines for seismic design of cut-and-cover tunnels to overcome the drawbacks in the existing Caltrans design specification and tools. The research work involves intensive dynamic tests for the 1/9 scale steel tunnel specimen (4 ft height, 6 ft width, and 9 ft long in model scale), that is adopted from the Doyle Drive Battery Tunnel (reinforced concrete structure, San Francisco, CA). The tunnel model is fully buried at shallow depth (2 ft) in dry soil using a large scale laminar soil shear container, funded by the California Department of Transportation. The container consists of 31 steel laminar frames, each separated by a steel roller system to allow for uni-directional displacement. Dimensions of the container are a length of 22 ft, a width of 9.6 ft, and a height of 15.2 ft. The tunnel and soil will be extensively instrumented to acquire measurements of accelerations, displacements, strains, earth/soil pressures, etc, during the shaking. Each soil-foundation system will be tested under a series of earthquakes starting with slow motions with low amplitude and culminating with severe earthquake motions (e.g., Northridge record, M=6.7). The outcome of this research will ensure that future cut-and-cover tunnels are designed to a higher performance standard and existing systems are upgraded to offer satisfactory performance.