In 2010, DA Smith (formerly Agapito Associates, Inc. Field Services) completed core drilling in support of rehabilitation of Cross Passage 5 in the Colorado Department of Transportation’s Hanging Lake Tunnel near Glenwood Springs, Colorado. DA Smith mobilized core-drilling equipment to characterize the ground conditions behind the shotcrete lining and to provide a basis for design of the remediation of the cross passage.
A total of 15 continuous core holes were drilled horizontally into the rib, at +45° into the spring line, and vertically into the roof of the tunnel cross passage. The coring tools used were NW conventional, 2.06-inch-diameter core, and 2.985-inch-diameter borehole.
Drilling was completed with zero discharge of drilling fluids. A summary report was prepared which included full descriptions of the core, videologs, and recommendations for rehabilitation of the tunnel.
DA Smith later conducted additional core drilling to confirm the effectiveness of remediation grouting. DA Smith installed RMT Telltales in the confirmation drill holes to measure tunnel convergence and monitor the stability of the tunnel.