USE OF FLOW-NET IN EARTH DAM AND LEVEE DESIGN

A BRIEF REVIEW IS PRESENTED OF MANY POSSIBLE APPLICATIONS OF THE FLOW-NET TO EARTH DAM AND LEVEE DESIGN SUGGESTING SOME TECHNIQUES OF CONSTRUCTING FLOW-NETS, PARTICULARLY THOSE HAVING AN INDETERMINATE PHREATIC LINE. FLOW OF WATER THROUGH SOIL MASSES IS BUT ONE OF THE NUMBER OF FORMS OF STREAM-LINE FLOW THAT CAN BE STUDIED WITH THE FLOW-NET. THIS STUDY IS CONCERNED ONLY WITH SEEPAGE THROUGH SOIL. THE FLOW- NET WHEN APPLIED TO SEEPAGE THROUGH SOIL IS BASED UPON THE ASSUMPTION THAT DARCY'S LAW IS VALID, THAT THE SOIL MASS IS HOMOGENEOUS AND THE VOIDS COMPLETELY FILLED WITH WATER AND THAT THE QUANTITY OF WATER CONTAINED IN ANY SMALL VOLUME DOES NOT CHANGE WITH TIME. THESE CONDITIONS PROVIDE THE BASIS FOR DERIVATION OF A LAPLACE DIFFERENTIAL EQUATION FOR STEADY SEEPAGE THROUGH SOIL. THE FLOW-NET MUST HAVE THE FOLLOWING GENERAL PROPERTIES: (1) IS COMPOSED OF FLOW-LINES AND EQUIPOTENTIAL LINES INTERSECTING AT RIGHT ANGLES TO FORM AREAS THAT ARE BASICALLY SQUARES, (2) THE HEAD LOSS BETWEEN ADJACENT EQUIPOTENTIAL LINES IS CONSTANT, AND (3) THE QUANTITY OF SEEPAGE BETWEEN ADJACENT PAIRS OF FLOW-LINES IS CONSTANT. THE FLOW-NET PROVIDES A MEANS OF ESTIMATING THE POSITION OF THE SATURATION LINE WITHIN EMBANKMENTS, AND THE DISTRIBUTION OF SEEPAGE FORCES AND UPLIFT PRESSURES THROUGHOUT. THREE FACTORS HAVE MAJOR INFLUENCE UPON THE POSITION OF THE SATURATION LINES AND THE DISTRIBUTION OF SEEPAGE FORCES AND PRESSURES IN EARTH DAMS AND LEVEES: (1) THE DISTRIBUTION OF SOIL MASSES WITHIN THE EMBANKMENT, (2) THE DEGREE OF STRATIFICATION OF THE EMBANKMENT AND FOUNDATION, AND (3) THE POSITION AND CHARACTER OF DRAINS, BLANKETS, ETC., IN FOUNDATIONS. RECOGNIZING THE LIMITATIONS OF THEORETICAL ANALYSIS METHODS, THE FLOW-NET CAN BE OF HELP IN STUDYING THE RELATIVE ADVANTAGES OF DIFFERENT DESIGN FEATURES, AND IN ESTABLISHING ECONOMICAL AND SAFE DESIGNS FOR EARTH DAMS AND LEVEES.

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Filing Info

  • Accession Number: 00204138
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 12 1994 12:00AM