SYMPOSIA PAPER Published: 01 January 1965

Instrumentation for Movements Within Rockfill Dams


Methods of operating, installing, and obtaining field data with the slope indicator and the settlement torpedo are described. The slope indicator, a pendulum-activated inclinometer lowered inside a grooved extruded aluminum casing, can measure inclination to 1 min of arc. Vertical movements are detected with a settlement torpedo which measures the elevation of joints of the aluminum casing. Conclusions from field tests performed at several rockfill dams are: (1) vertical movements are 5 to 10 times as great as horizontal movements, (2) down-slope movements develop in the core parallel to the axis and are maximum at about the lower one-third point of the section, (3) there is no movement at the point of contact between a smooth rock abutment and a rockfill, (4) lateral spreading as well as down-slope movement develop in the shells of rockfills, and (5) the compressibility of a well-compacted rockfill is slightly less than that of a wellcompacted clay core, whereas a poorly compacted rockfill is considerably more compressible.

Author Information

Wilson, S., D.
Shannon & Wilson, Inc., Seattle, Wash.
Hancock, C., W.
Slope Indicator Co., Seattle, Wash.
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Developed by Committee: D18
Pages: 115–130
DOI: 10.1520/STP41282S
ISBN-EB: 978-0-8031-6011-8
ISBN-13: 978-0-8031-6165-8