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Geologic and geotechnical considerations for pressure tunnel design
The design of pressure tunnels for hydroelectric projects or other water conveyance systems requires the understanding of a number of geologic and geotechnical variables that include rock permeability, rock modulus, susceptibility of the rock to erosion or solution, and in-situ minimum rock stress. The definition of the groundwater table also is a key element for the design. Given the number of pressure tunnels constructed over the last 25 to 30 years that have not performed in a satisfactory manner, a review of the essential design requirements and geologic and geotechnical parameters is required and is given herein. Where the ground conditions have not been adequately addressed, excessive leakage of high pressure water has occurred during first filling and subsequent operation. The loss of water may be of such magnitude as to be financially unacceptable and the introduction of quantities of high pressure water into the rock mass may present hazards to adjacent facilities. The costs involved in tunnel lining repair as a result of an inadequate definition of the rock conditions have been substantial in terms of lost energy generation, interrupted water supply to major centers of population, and for repairs done under difficult conditions. Because the cost of tunnel linings represents a major percentage of the total tunnel investment, the optimization of the lining design is an essential element of any water conveyance project.
Geologic and geotechnical considerations for pressure tunnel design
The design of pressure tunnels for hydroelectric projects or other water conveyance systems requires the understanding of a number of geologic and geotechnical variables that include rock permeability, rock modulus, susceptibility of the rock to erosion or solution, and in-situ minimum rock stress. The definition of the groundwater table also is a key element for the design. Given the number of pressure tunnels constructed over the last 25 to 30 years that have not performed in a satisfactory manner, a review of the essential design requirements and geologic and geotechnical parameters is required and is given herein. Where the ground conditions have not been adequately addressed, excessive leakage of high pressure water has occurred during first filling and subsequent operation. The loss of water may be of such magnitude as to be financially unacceptable and the introduction of quantities of high pressure water into the rock mass may present hazards to adjacent facilities. The costs involved in tunnel lining repair as a result of an inadequate definition of the rock conditions have been substantial in terms of lost energy generation, interrupted water supply to major centers of population, and for repairs done under difficult conditions. Because the cost of tunnel linings represents a major percentage of the total tunnel investment, the optimization of the lining design is an essential element of any water conveyance project.
Geologic and geotechnical considerations for pressure tunnel design
Merritt, A.H. (author)
1999
16 Seiten, 8 Quellen
Conference paper
English
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