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|Title:||Verification of empirical method for determining riverbank stability, 1960 data|
|Authors:||United States. Mississippi River Commission.|
U.S. Army Engineer Waterways Experiment Station.
|Publisher:||U.S. Army Engineer Waterways Experiment Station.|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Potamology investigations report ; no. 12-11.|
Summary: This report is the eighth of a series in which new data obtained from borings made for revetment construction are analyzed to determine the applicability of the empirical method for predicting riverbank stability with regard to flow failure. Data obtained in fiscal year 1960 are analyzed, and stability predictions are made for 11 new areas. Failures during 1960 at 11 sites previously analyzed also are discussed. Based on analyses made in 1958 of previous performance data, the classification criteria for overburden soils, zone A sands, and zone B sands were modified. The failures at sites previously studied, new site predictions, and current year performance are analyzed using the modified criteria. During 1960, 14 bank failures (6 flow failures and 8 shear failures) were reported along the Mississippi River near 15 boring locations at 11 sites for which stability predictions had been made. Four flow failures occurred near three boring locations predicted to be susceptible to flow failure. A fifth flow failure occurred near one boring location where the full thickness of zone A sand had not been determined and could not be used for verification of the stability criteria. A sixth flow failure was near two boring locations, one of which could not be used to verify the stability criteria because the full depth of zone A sand was not determined and one of which was predicted to be susceptible to flow failure. Seven shear failures occurred near seven boring locations predicted to be stable with regard to flow failure. An eighth shear failure occurred near two boring locations, one of which was predicted to be unstable and the other stable. Since 1954 when riverbank stability predictions were initiated, data have been studied from 674 boring locations at 78 revetment sites on the Mississippi River in the Memphis and Vicksburg Districts. Flow failures have occurred at 7 boring locations in the Memphis District and 23 boring locations in the Vicksburg District. Of the 30 locations where flow failures have occurred, 24 were predicted to be unstable according to the modified criteria. Five flow failures have occurred at boring locations for which no prediction can be made since the full depth of zone A sand was not determined during the field investigation. One flow failure occurred near a location predicted to be stable, but in this one case the failure was more than 800 ft from the boring and the boring data may not be representative of the soil conditions at the failure location. The modified classification criteria have proved reliable in predicting flow failure. However, many locations predicted to be unstable have not experienced flow failure, and it is possible that either the density of zone A sand may be such that flow failure will not occur, or that the severity of river attack has not been sufficient to initiate flow failure.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Potamology Investigations Report|
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|Potamology-Investigations-Report-No-12-11.pdf||7.51 MB||Adobe PDF|