Session Start Date

5-6-1984

Abstract

Landslides occurred in the Bearpaw shale slope adjacent to the powerhouses at Fort Peck Dam in the geologic past. Excavation of the slope toe for construction of reservoir outlet works in 1934 initiated progressive sliding of colluvium which continued to 1974. The active slide area had an average movement rate of 4 ft/yr from 1944-1945 and average movement rates of 1-2 ft/yr from 1953-1971. These movements caused no distress to the powerhouses or other facilities. In 1974, the slope was stabilized by excavating 1.6 x 106 cu. yd. of material, resulting in a 1 on 6 overall slope. A field residual strength given by c' = 0.1 ksf, Φ' = 10° or c' = 0, Φ' = 11.5° for effective normal stresses of 3-4 ksf was calculated from the slides using 1950's topography and groundwater levels.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

First Conference

Publisher

University of Missouri--Rolla

Publication Date

5-6-1984

Document Version

Final Version

Rights

© 1984 University of Missouri--Rolla, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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May 6th, 12:00 AM

Powerhouse Slope Behavior, Fort Peck Dam, Montana

Landslides occurred in the Bearpaw shale slope adjacent to the powerhouses at Fort Peck Dam in the geologic past. Excavation of the slope toe for construction of reservoir outlet works in 1934 initiated progressive sliding of colluvium which continued to 1974. The active slide area had an average movement rate of 4 ft/yr from 1944-1945 and average movement rates of 1-2 ft/yr from 1953-1971. These movements caused no distress to the powerhouses or other facilities. In 1974, the slope was stabilized by excavating 1.6 x 106 cu. yd. of material, resulting in a 1 on 6 overall slope. A field residual strength given by c' = 0.1 ksf, Φ' = 10° or c' = 0, Φ' = 11.5° for effective normal stresses of 3-4 ksf was calculated from the slides using 1950's topography and groundwater levels.