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|Title:||Verification of empirical method for determining riverbank stability, 1965 data|
|Authors:||United States. Mississippi River Commission.|
Caldwell, W. K.
Calhoun, Charles C., 1946-
|Publisher:||U.S. Army Engineer Waterways Experiment Station.|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Potamology investigations report ; no. 12-18.|
Summary: This report is the thirteenth 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 in 1965 are analyzed, and stability predictions are made for 14 new areas. Failures during 1965 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. During 1965, 21 bank failures along the Lower Mississippi River at 12 revetment sites occurred within 500 ft of boring locations for which stability predictions had been made. Nine flow failures occurred near nine boring locations predicted to be susceptible to flow failure. Two flow failures occurred near two boring locations predicted to be stable with regard to flow failure. The other ten failures were classified as shear failures. Of the shear failures, two occurred near boring locations predicted to be unstable with regard to flow failure, and eight near boring locations predicted to be stable with regard to flow failure. Since 1954 when riverbank stability predictions were initiated, data from 1108 boring locations at 99 revetment sites on the Mississippi River in the Memphis and Vicksburg Districts have been studied. Flow failures have occurred within 500 ft of 13 boring locations in the Memphis District and within 500 ft of 35 boring locations in the Vicksburg District. Of these 48 locations where failures have occurred, 39 had been predicted to be unstable according to the modified criteria. Six flow failures have occurred at boring locations for which no prediction could be made because of insufficient data on the depth of zone A sand. Flow failures have occurred at only three boring locations predicted to be stable. The modified criteria have proved reliable, with only three exceptions, in predicting flow failure. However, many locations predicted to be unstable have not experienced flow failure, and it is possible that the density of zone A sand may be such that flow failure will not occur, the severity of river attack has not been sufficient to initiate flow failure, or the influence of other factors which could prevent such failures has not been taken into account.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Documents|
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