A hydraulic model, constructed at an undistorted scale of 1:120, reproduced about 1 mile upstream of the dam and about 1200 ft downstream of the dam for the purpose of determining the magnitude of wave heights, runup, and overtopping of the dam for four potential landslides. These potential landslides were located from 160 to 2100 ft upstream of the dam and contained potential landslide volumes of about 900,000 to 4,750,000 cu yd. The model reproduced contours to a maximum elevation of 2700 ft msl and had an adjustable mechanical inclined plane to support the landslide material above el 2700. The model landslide material primarily consisted of 1/18-cu-ft bags of iron ore and lead mixed to reproduce the correct rock mass density. These bags were hand-stacked up the inclined plane slope to obtain the correct elevation-volume-shape relationship, held in place mechanically, and then released to slide into the model under the influence of gravity. A few tests also were conducted with gravel and concrete cubes as the landslide material for comparison with the results of the bag tests. Results of the model study showed the wave amplitudes, runup, and downstream water expected at various reservoir pool elevations as a function of landslide parameters. It was concluded from the model study that: (A.) full volume landslides caused unacceptable conditions at the dam for pool elevations tested, depending on the landslide velocity; (B.) partial landslide failures (both upper and lower portions) also generated unacceptable conditions at the dam; (C.) the use of small concrete cubes and gravel as model landslide material in general generated higher and lower wave characteristics, respectively, than the landslides of bagged material; (D.) wave suppressors at the right abutment were not completely effective; and (E.) buttressing of the landslide toe area reduced the velocity of the potential landslide, thus resulting in a significant decrease in wave amplitude (however, larger wave heights were generated than for the normal rock rib with a comparable velocity). It is recommended that additional basic research be conducted to provide analytical methods of predicting landslide-generated waves. Details and results of the model friction tests are described and reported in Appendix A. Detailed wave data for all tests are reported in Appendix B. The location and elevation of maximum runup for each test are reported in Appendix C._x000D_ _x000D_ NOTE: This file is large. Allow your browser several minutes to download the file.


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    Title :

    Potential Landslide-Generated Water Waves, Libby Dam and Lake Koocanusa, Montana : Hydraulic Model Investigation



    Published in:

    Publication date :

    1974


    Size :

    13569201


    Type of media :

    Report


    Type of material :

    Electronic Resource


    Language :

    English



    Classification :


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