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Book Chapter

Trenching as an exploratory method

By
Allen W. Hatheway
Allen W. Hatheway
Haley & AIdrich, Inc., 238 Main Street, Cambridge, Massachusetts 02142
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F. Beach Leighton
F. Beach Leighton
Haley & AIdrich, Inc., 238 Main Street, Cambridge, Massachusetts 02142
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Published:
January 01, 1979

Abstract

The critical nature of siting nuclear power plants has led to increased emphasis on exploratory trenching. Trenching is the most definitive of all subsurface exploratory methods; it permits inspection of a continuous geologic section by both geologists and regulatory authorities and makes possible the preparation of a graphic log that delineates both obvious and subtle geologic features. About one of every two nuclear plant licensing efforts utilizes exploratory trenching. Many geologic hazards, such as "capable" faults, can be detected from trench exposures; they may otherwise remain undetected.

Trenches must be judiciously located, survey-controlled, excavated safely and adequately shored, logged in detail, and properly diagnosed. Useful techniques of trench logging include thorough cleaning of the trench walls, teamwork between geologist and recorder, logging against a carefully surveyed baseline and vertical reference grid, and panoramic photography. Soils, including paleosols, and glacial and glaciofluvial deposits present some of the most difficult media to log.

Trench logs must be thoroughly interpreted and correlated so that they document the geologic conditions governing suitability of the site. Age-determination techniques utilized in exploratory trenching include petrographic analyses, quartz inclusion studies, clay mineralogic analyses, and radiometric methods.

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Contents

GSA Reviews in Engineering Geology

Geology in the Siting of Nuclear Power Plants

Allen W. Hatheway
Allen W. Hatheway
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Cole R. Mcclure
Cole R. Mcclure
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Geological Society of America
Volume
IV
ISBN electronic:
9780813758046
Publication date:
January 01, 1979

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