Rapid Excavation in Hard Rock: A State-of-the Art Report.
Proc Deep Tunnels in Hard Rock-a Solution to Comb Sewer Problems EPA PP 187-219 :187-219
This paper describes the evolution of present day tunnel-boring techniques. Emphasis is directed toward selected cases from the past decade which are discussed in some detail. The data presented has, in many cases, been generated by Bureau of Mines personnel during on-site studies of the particular job. Wherever feasible, samples of the rocks being bored were returned to the Twin Cities Mining Research Center for determination of the physical properties. This paper presents the significant problems and accomplishments for various actual operations. Wherever possible, it presents physical characteristics of the rock encountered to aid the reader in evaluating rock hardness.
Proc., Deep Tunnels in Hard Rock-a Solution to Comb. Sewer ... Problems. EPA, PP. 187-219