Please use this identifier to cite or link to this item: https://hdl.handle.net/11681/20664
Title: Verification of empirical method for determining riverbank stability : report 12-24, 1974-1977 data
Authors: Soils and Pavements Laboratory (U.S.)
United States. Mississippi River Commission
Gann, Albert R.
Keywords: Bank stability
Soil liquefaction
Waterways
Riverbanks
Embankments
Revetments
Mississippi River
Borings
Empirical method
Publisher: Geotechnical Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Miscellaneous Paper
Abstract: This report is the nineteenth of a series in which new data obtained from borings made for revetment construction are analyzed to determine the applicability of an empirical method for predicting riverbank stability with regard to flow (liquefaction) failure. Boring data obtained from 1974 through 1977 are analyzed, and stability predictions are made at 47 new areas. Failures that occurred from 1974 through 1977 at sites previously analyzed also are discussed. Based on analyses made in 1958 of previous performance data, the classification criteria for zone A and zone B sands were modified in 1959. The failures at sites previously studied, new site predictions, and current year performance are analyzed using the modified criteria. From 1974 through 1977, 52 bank failures (29 flow-type and 23 shear-type) occurred along the lower Mississippi River at 37 revetment sites within 50 ft of boring locations for which stability predictions with regard to flow failure had been made. There were 23 flow failures near 23 boring locations predicted to be unstable, two flow failures near two boring locations predicted to be stable, four flow failures occurred near four boring locations for which no prediction was possible because the thickness of zone A sand had not been determined. Fourteen shear failures were reported near 13 boring locations predicted to be stable, seven shear failures were reported near seven boring locations predicted to be unstable, and two shear failures were reported near two boring locations for which no prediction was possible because boring depth was not sufficient and zone A sand had not been penetrated. In addition, 30 failures occurred that could not be classified as to type of failure and were judged to be the direct result of severe local scour. Also, 18 flow failures and 28 shear failures were reported in areas where no borings were located within 500 ft. From 1954 (when riverbank stability predictions were initiated) through 1977, 2312 boring locations at 264 revetment sites on the Mississippi River have been studied. The majority of the borings were in the Vicksburg and Memphis District areas. Data on sites in the New Orleans District were included only in the first report of this series (Report 12-3) . However, boring data beginning in 1968 from the New Orleans District are included herein. Flow failures reported through 1977 have occurred within 500 ft of 27 boring locations in the Memphis District and 177 boring locations in the Vicksburg District; of these, 164 occurred near locations that had been predicted to be unstable according to the modified criteria, 26 occurred at boring locations predicted to be stable, and 14 occurred at boring locations for which no prediction had been made because the thickness of zone A sand had not been determined. The modified criteria have proven reliable in predicting stability with regard to flow failure. Of the total of 204 flow failures recorded since 1954 within 500 ft of analyzed borings, 26 failures (19 violations of criteria or 9 percent) were near boring locations predicted to be stable. However, many locations predicted to be unstable have not experienced flow failure, and it is possible that either the density of the zone A sand may be such that flow failure will not occur or the severity of river attack has not been sufficient to initiate flow failure.
Rights: Approved for public release; distribution is unlimited.
URI: http://hdl.handle.net/11681/20664
Appears in Collections:Miscellaneous Paper

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