Harlan, Kentucky Diversion Tunnels

Abstract

As a part of a local flood protection scheme, the Nashville District of the U. S. Army Corps of Engineers is planning to divert the full flow of Clover Fork of the Cumberland River around the central business district of the city of Harlan, Kentucky. This is to be accomplished by constructing four tunnels side by side through a meander ridge that has a maximum overburden above the tunnels of approximately 325 ft (99 m) and averages about 217 ft (66 m). The inverted “U” configured tunnels are 32 ft (9.8 m) high, 34 ft (10.4 m) wide and average 1,935 ft (590 m) in length. The rock through which they are to be constructed is Pennsylvanian age silt-stone with an average compressive strength of about 6,000 psi and containing about 57 percent quartz. As a part of the exploratory program, horizontal borings, each being more than 1,000 ft (305 m) in length, were made from each portal location. Most of the rock mass explored has RQD values in excess of 95 percent with zones in excess of 300 ft (91 m) in the horizontal holes being devoid of any discontinuities. Construction is to be accomplished with a road header mining machine with rock support being furnished by systematic rock bolting. Four inches of steel fiber reinforced shotcrete will be applied as the permanent lining for the tunnels.