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Title: Effect of reservoir filling on stresses and movements in earth and rockfill dams : a report of an investigation
Authors: University of California, Berkeley. College of Engineering. Office of Research Services.
Nobari, E. S.
Duncan, J. M. (James Michael)
Keywords: Embankments
Hydrostatic pressure
Earth dams
Soil mechanics
Publisher: U.S. Army Engineer Waterways Experiment Station.
Engineer Research and Development Center (U.S.)
Description: Contract Report
Abstract: The primary objective of this research was to develop analytical procedures which may be used to analyze the effects of reservoir filling on the stresses and movements in earth and rockfill dams. This study also includes a review of the behavior of embankments during reservoir filling, and an experimental investigation of the effects of water on the properties of granular materials. Review of the published case histories indicates that reservoir filling has induced significant movements in many well-engineered large dams as well as in small dams. When these movements develop as differential movements in dams and foundations, cracking and consequent erosion and failures have been observed in a number of dams. One of the major factors contributing to the development of differential movements during reservoir filling is the compression due to wetting which occurs in a wide variety of different types of soils. An experimental investigation was undertaken to study the effects of wetting on properties of granular material similar to those used in rockfill dams. The study showed that moisture had a considerable effect on strength, compressibility, stress-strain and volume change characteristics of the materials tested. A new procedure was developed to analyze the effects of water on soil masses which "soften" and undergo movements and/or stress changes when wetted. This procedure employs the properties of the soil determined by laboratory triaxial tests conducted on specimens prepared at the pre-wetting water content and at the anticipated water content after wetting. This procedure may also be used to analyze the effects of "softening" caused by factors other than water, such as movements due to creep of soil. The procedures developed to analyze the effects of wetting were incorporated in a plane strain finite element computer program, which is also capable of representing other effects of water such as seepage and buoyant loads for soil masses with arbitrary shapes and boundary conditions. The capabilities and effectiveness of the procedures developed were evaluated by comparing the calculated results with the measured strains and stress changes induced in laboratory test specimens by wetting. Movements and stress changes in Oroville Dam caused by reservoir filling were also analyzed, and the calculated values were compared to the measured ones. These comparisons indicate that the procedures developed are capable of predicting the complex behavior of dams during reservoir filling to a reasonable degree of accuracy.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Contract Report

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