In 2018, DA Smith (formerly Agapito Associates, Inc.) conducted specialized around-the-clock core drilling inside the Caldecott heavy rail commuter train tunnel operated by the Bay Area Rapid Transit (BART) authority. Exploration drilling was conducted on behalf of Earth Mechanics, Inc. for the purpose of characterizing fault-related squeezing conditions affecting concrete liner stability. Careful coordination was required with BART and others to mobilize and operate inside the active tunnel. The drill and crews accessed the tunnel and drilled off the deck of a mobile BART rail car.
High quality HQ core samples were obtained through the reinforced concrete liner, fault gouge, and fractured rock mass. Texam pressuremeter tests were conducted in the boreholes to measure the in situ stiffness of the surrounding ground.