Please use this identifier to cite or link to this item: https://hdl.handle.net/11681/4976
Title: Empirical study of behavior of clay shale slopes. Volume 1
Authors: Fleming, Robert W.
Spencer, G. S.
Banks, D. C. (Don Charles)
Keywords: Nuclear construction engineering
Nuclear cratering
Nuclear construction technology
Slope stability
Clay shale
Publisher: U.S. Army Engineer Nuclear Cratering Group
Engineer Research and Development Center (U.S.)
Description: Technical report
Abstract: This study was undertaken to determine the factors that lead to instability in clay shale to provide a basis for assessing the probable long-term stability of high crater slopes in clay shales. The chief features contributing to the engineering behavior of clay shales are degree of overconsolidation and lithology, both of which reflect geologic history. Local geologic structure and hydrologic conditions affect individual slopes. Weak layers may present slope hazards, while conversely a few stronger layers may materially strengthen an entire clay shale slope. Time-dependent phenomena are important in clay shale slopes, which may fail after standing apparently stable for many years Intensive studies were conducted of natural slopes in five clay shale units in the upper Missouri Basin. The Claggett, Bearpaw, and Pierre formations, all marine deposited shales of Late Cretaceous age, showed extensive slope failures; high slopes generally stood at overall inclinations of only 5 to 10 degrees, which are comparable to the residual angles of internal friction of the materials. The Cretaceous Colorado group and Lower Tertiary Fort Union group showed steeper slopes with fewer failures. Intensive laboratory testing of physical properties of all materials indicated that only gross differences in slope behavior can be related to any specific test or series of tests. Engineering practice in clay shale materials is customarily based on an empirical approach, attention being given to local site conditions and to the observed behavior of existing nearby slopes. Limited observations of experimental crater slopes in clay shale are available. The conclusion is reached that future design crater slopes must be based on experiences with conventionally excavated slopes. Furthermore, the design of cratered slopes must be conservative, although no experience indicates that the slope inclination needs to be as flat as the residual angle of internal friction of the site materials.
Rights: Approved for public release; distribution is unlimited.
URI: http://hdl.handle.net/11681/4976
Appears in Collections:Technical Report

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