Sinking a Large-Diameter Concrete-Lined Access Shaft: Harold D. Roberts Tunnel, Colorado Page: 1
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SINKING A LARGE-DIAMETER, CONCRETE-LINED ACCESS SHAFT:
HAROLD D. ROBERTS TUNNEL, COLORADO1
R. L. Bolmer2
This information circular describes the application of modern methods
and equipment in sinking a vertical, 916-foot-deep by 16-foot-diameter,
concrete-lined access shaft for the Harold D. Roberts tunnel near Montezuma,
Colo. Although the access shaft was merely a construction facility to
expedite completion of a 23-mile water-diversion tunnel, a circular shaft
of this type would be equally adaptable for mine development or other
purposes. Comparable sinking methods and equipment could be used for similar
shafts within a wide range of sizes and depths.
In addition to excavation and support of the basic access shaft to
tunnel grade, the overall sinking project involved initial preparation of a
surface site and plant, subsequent construction of a tunnel-level station
and loading pocket at the shaft bottom, and ultimate conversion of the basic
shaft into a hoisting and access facility for tunnel operations. The sinking
period for the basic shaft approximated one year. Actual tunnel operations
through the converted shaft began on April 3, 1958, approximately 19 months
after the project was initiated.
The shaft, which was collared October 11, 1956, was first extended to
a depth of 140 feet using preliminary methods, lightweight equipment, and
temporary facilities. Sinking was suspended between February 2 and March 6,
1957, while the headframe was erected and other permanent collar facilities
were installed. Completion of these facilities permitted the use of larger
equipment and more efficient sinking methods in the remainder of the shaft.
Subsequent operations continued without interruption until the ultimate
depth of 916 feet (tunnel grade) was reached on September 30, 1957.
1 Work on manuscript completed November 1960.
2 Mining methods research engineer, Denver Mining Research Center, Bureau of
Mines, Denver, Colo.
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Bolmer, R. L. Sinking a Large-Diameter Concrete-Lined Access Shaft: Harold D. Roberts Tunnel, Colorado, report, 1961; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc170737/m1/9/: accessed January 16, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.