Please use this identifier to cite or link to this item: https://hdl.handle.net/11681/20631
Title: Seepage in Mississippi River banks. Report 1, Analysis of transient seepage using a visous-flow model and the finite difference and finite element methods
Authors: United States. Army. Corps of Engineers. Lower Mississippi Valley Division
Desai, C. S. (Chandrakant S.), 1936-
Keywords: Finite difference method
Finite element method
Seepage
Numerical models
Mathematical models
Mississippi River
Parallel plate model
Riverbanks and earth dams
Transient unconfined seepage
Revetments
Levees
Publisher: Soils and Pavements Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Technical Report
Abstract: The stability of the banks of the Mississippi River is dependent in part upon seepage conditions induced by variations in the river level. Specifically, the drawdown conditions be come significant for the design of stable riverbank slopes and protective structures. Conventionally, the slopes are designed on the basis of sudden drawdown conditions, which have often been found to be conservative. For realistic design analysis, it is necessary to evolve methods that permit computations of the timewise fluctuations of the phreatic surface as a consequence of the variations in the river level. Closed-form solutions for the transient, unconfined seepage posed by the foregoing situation are suitable only for simplified geometries and physical conditions. Such numerical techniques as the finite difference and finite element methods can provide general solutions for complex geometries and material properties. These methods were employed in this research. A parallel-plate, viscous-flow model was designed and constructed at the WES for the purpose of conducting tests that simulate seepage conditions and variations of external water levels in the field. This report presents a description of the viscous-flow model and the theory governing fluid flow through the model. Various experiments were performed using the model, and a special finite difference scheme was developed for solving approximate equations governing one- and two-dimensional fluid flow. Comparisons were made between the numerical and experimental solutions. A study was performed to examine the numerical characteristics of the finite difference solution scheme. The finite element method for analysis of one- and two-dimensional fluid flow situations was developed. The one-dimensional flow situation was based on an approximate equation, and the two-dimensional situation was based on the division of the transient problem into a number of steady-state problems governed by the Laplace equation. The numerical solutions were compared with typical experimental results and with field observations along typical sections of the Mississippi River. Analyses were also performed to arrive at the conclusions regarding discretization of infinite soil media as occurring in riverbanks. Applications of the proposed techniques for obtaining head distribution and flow nets in the domain of fluid seepage are presented in the report. Work to be performed and to be included in the final report (Report 2) is briefly described.
Rights: Approved for public release; distribution is unlimited.
URI: http://hdl.handle.net/11681/20631
Appears in Collections:Technical Report

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