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Geotech students get in-depth view of tunneling project

1/22/2009 4:34:00 AM

Civil engineering students in a graduate-level geotechnical course got an in-depth look at one of the nation’s most unique tunneling projects, the Devil’s Slide Tunnels Project in California, when they took a class field trip to the Pacifica, Calif., area in December 2008.

The trip was the culmination of CEE598 TSR Tunneling in Soil and Rock.  Through a unique instructional arrangement, the class was taught by CEE Associate Professor Youssef Hashash and CEE Professor Emeritus Edward J. Cording, who took time out of his busy consulting practice to co-teach the class pro-bono.  Four times during the semester, Cording flew in from his home in Savannah, Ga., to present two four-hour lectures on Friday evening and Saturday morning. 

"It was really out of his dedication and commitment to Illinois that he did this," Hashash says.  "And the students benefited tremendously."

Located along the California coast between Pacifica and Montara, the geologically unstable Devil’s Slide region is notorious for rock- and land slides.  Where the Pacific Coast Highway, Route 1, crosses this region, there has been a long history of road closures.  In 1995, the road was closed for 158 days and cost almost $3 million to repair, according to the California Department of Transportation (Caltrans).

Caltrans' Devil's Slide Tunnels Project will allow Route 1 to bypass this region through two inland tunnels being constructed beneath San Pedro Mountain.  Each tunnel is 30 feet wide and 4,200 feet long.  A 1,000-foot bridge and a realignment of the roadway are also planned.  The project is scheduled for completion in 2011.

The complexity of the geology at the site, which includes various kinds of rock and several fault zones, makes the tunneling project uniquely challenging and an excellent one for students to study, Hashash says.

Cording is a National Academy of Engineering member and a world authority on tunneling in rock and soil, urban heavy construction, and the effects of excavation on building damage.  Through his consulting activities, he had contacts in the Devil's Slide project and was able to arrange for the unique field trip.

Hashash is an expert in numerical analysis techniques and the seismic response of tunnels, and he has years of experience in tunneling, both through industry practice and research.

Throughout the semester, the students, 17 in all, worked on group projects to develop both static and seismic designs for one of two real-life projects, the Devil's Slide project and the Beacon Hill Tunnel project in Seattle.  The class culminated with the field trip to California December 4-7.  There was no cost to most of the students for the trip; it was funded by the CEE department and a generous gift by Cording.

The trip was structured so that students were introduced to the project as practicing design engineers would view it, Hashash says.  First they examined rock cores from borings and hiked up the mountain to view the site.  Later they visited the tunnel itself and observed the sequential excavation method in progress.  They had meetings with geologists, Caltrans design engineers, and construction engineers for the contractor.  Finally, they presented their designs to an audience that included engineers on the project.

"It was really just a fantastic experience—a unique experience," Hashash says.  "It will be something the students will remember for many years.  We were able to offer our students a very unique perspective and hence, hopefully, an edge in engineering practice," he says.