Structural Engineering

Aerospace Biological Civil Geotechnical Mechanical


Sequential Excavation Method (SEM) for the San Diego Courthouse Commons Tunnel Project

Seminar Speaker
Tom Pennington, PE, P.Eng, M. ASCE
Seminar Date
Monday, Feb 28, 2022 - 12:00 pm
Seminar Location - Room
Warren Lecture Hall 2204
Speaker Bio

Tom Pennington is the Geotechnical Design Specialty Leader with Brown and Caldwell based in San Francisco. He has over 20 years of experience in geotechnical design and construction for a wide range of underground projects, including transit, water, wastewater, and power facilities. He is a registered civil engineer in California, New York, and Hawaii, and he holds MS and BS degrees in Civil & Environmental Engineering from the University of Illinois at Urbana–Champaign. Tom is also the current chair of the ASCE Geo-Institute’s Underground Engineering and Construction Technical Committee.

This seminar will present the recent application of Sequential Excavation Method (SEM) tunneling techniques used for construction of the Courthouse Commons (COCO) Tunnel in downtown San Diego. The COCO Tunnel is a component of the larger Courthouse Commons Development Project and involved construction of a 300-foot long, 28-foot diameter tunnel located directly beneath an existing multi-story building. Tunneling required strict controls on excavation methods to minimize the potential for ground settlement, and flexibility to adapt to variable conditions which are common to underground construction in congested urban settings. The tunnel was further challenged by crossing of an active fault zone which required an innovative design approach utilizing seismic joints to accommodate up to 18 inches of potential fault displacement. This presentation will discuss design and construction challenges for the project and will include a short video (“tunnel tour”) that will provide an in-depth look at the project’s construction.

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