Geotechnical investigation and preliminary design underway for $150 million Austin Formation limestone twin 3-lane tunnels of 3 km and 2.4 km beneath junction of LBJ Freeway with Dallas North Tollway to provide additional high occupancy vehicle lanes to relieve traffic congestion. Cross-section of 146 sq m will be supported by rockbolts and fibre-reinforced shotcrete finished with a 300 mm-thick reinforced concrete lining with waterproof membrane. Client is Texas Department of Transportation, lead consultant is HNTB, and tunnel designer is Lachel & Associates, Denver, CO. Visit www.lachel.com June 2000.
