Development of Tunneling Methods and Controls

Improvements in equipment and methods during the past 15 years have kept tunnel excavation costs from appreciable increases while the general construction cost index has doubled. Tunnel drilling rates have increased from 20 ft per week 100 year ago to 100 ft per week 50 years ago and to about 300 ft per week today. A milestone in tunnel driving was the 3-1/2-mile-long Fucinus Tunnel (19 ft wide and 9 ft high) started in A.D. 41 and requiring 30,000 slaves 11 years to complete. The concept to boring machines to drill tunnels goes back to 1882, but the greatest advance has been made in the last 5 years. A table lists the major completed mole tunneling project. Cost savings up to 40 % over conventional drill-shoot-muck cycle methods can be proven. The requirement for and types of tunnel supports being used are analyzed. A laser beam is an excellent control method for precision drilling with a boring machine. Tunneling safety has progressed to a satisfactory level. During a million man-hours at Blanco Tunnel, CO., only six minor list-time accidents occurred.