Verification of empirical method for determining riverbank stability, 1966 data
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Calhoun, Charles C., 1946-
Potamology ReportSummary: This report is the fourteenth 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 1966 are analyzed, and stability predictions are made for 12 new areas. Failures during 1966 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 1966, six bank failures along the Lower Mississippi River at four revetment sites occurred within 500 ft of boring locations for which stability predictions had been made. Two flow failures occurred at one site near two boring locations predicted to be stable with regard to flow failure. The other four failures were classified as shear failures in areas predicted to be stable with regard to flow failure . Four flow failures and numerous small shear failures were reported in areas where no borings were located within 500 ft. In addition, one failure location had been graded before a survey could be made and consequently the failure could not be classified. Since 1954 when riverbank stability predictions were initiated, data from 1212 boring locations at 101 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 37 boring locations in the Vicksburg District. Of these 50 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 five boring locations predicted to be stable. The modified criteria have proved reliable, with only five exceptions, 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 the severity of river attack has not been sufficient to initiate flow failure.
U.S. Army Engineer Waterways Experiment Station.Engineer Research and Development Center (U.S.)
Potamology; Mississippi River; Soils; Soil mechanics; Soil testing; Soil tests; Soil sampling; Soils data; Slope stability; River banks; Bank erosion; Methodology; Methods; Flow failure; Soil liquefaction; Revetments; Revetment failure; River banks
Potamology investigations report ; no. 12-19.
Approved for public release; distribution is unlimited.