DISCUSSION OF HORIZONTAL MOVEMENTS RELATED TO SUBSIDENCE

THE DISCUSSER COMPLIMENTS THE AUTHORS ON THE INTERESTING REPORT OF MODEL STUDIES AND THEORETICAL STUDIES SIMULATING THE SETTLEMENT OF AN EARTH DAM ALONG ITS LONGITUDINAL AXIS. HOWEVER, IT IS POINTED OUT THAT CRACKS THAT DEVELOP AT LOWER ELEVATIONS IN THE EMBANKMENT, OR IN THE UPPER FOUNDATION, ARE FAR MORE DANGEROUS AS POTENTIAL CAUSES OF CATASTROPHIC FAILURE OF THE DAM. STUDIES SHOULD BE EXTENDED TO MEASUREMENT OF STRAINS THROUGHOUT THE MODEL EMBANKMENT AND CORRELATED WITH SIMILAR MEASUREMENTS IN REAL DAMS. SINCE THE DESIGN OF A DAM IS A THREE-DIMENSIONAL PROBLEM, THE TRANSVERSE HORIZONTAL STRAINS, INDUCED IN A DIRECTION PERPENDICULAR TO THE LONGITUDINAL AXIS OF THE DAM, MUST ALSO BE INCLUDED. THE WRITER DISCUSSES TWO ASPECTS OF THE SUBJECT: THE MECHANICS OF SUBSIDENCE AND THE CREDIBILITY OF THE BEAM ANALOGY. IN DEDUCING TRANSVERSE HORIZONTAL STRAINS, PERPENDICULAR TO THE LONGITUDINAL AXIS OF THE DAM, BOTH SHEAR STRESS AND POISSON'S RATIO ARE IMPORTANT FACTORS TO BE CONSIDERED. THE DESIGN OF THE EMBANKMENT AND APPURTENANCES REQUIRES CONSIDERATIONS OF STRAINS IN BOTH DIRECTIONS. THEORETICAL ANALYSES BY RUTLEDGE AND GOULD INDICATE THAT THERE ARE THREE PHENOMENA THAT INDUCE TRANSVERSE HORIZONTAL STRAINS AT THE EMBANKMENT-FOUNDATION INTERFACE: (1) DEFLECTION OF THE INTERFACE UNDER VERTICAL LOADS (AS DEFINED BY THE SHAPE OF THE SETTLEMENT PROFILE), (2) THE POISSON EFFECT CAUSED BY THE VERTICAL LOADS, AND (3) OUTWARD DIRECTED SHEAR STRESSES INDUCED BY THE EMBANKMENT LOAD. THE COROLLARY DEDUCTIONS THAT THE BEAM ANALOGY MAY BE USED TO ESTIMATE STRAIN DISTRIBUTION AT THE SURFACE OF THE FOUNDATION NEED SOME EXAMINING. THE LOGIC OF THE USE OF THE BEAM ANALOGY REQUIRES THE ASSUMPTION THAT TENSILE STRAINS ARE INDUCED AT THE EMBANKMENT-FOUNDATION INTERFACE WHEREVER THE LONGITUDINAL SETTLEMENT PROFILE IS CONCAVE UPWARD. THIS ASSUMPTION IS NOT COMPATIBLE WITH OBSERVED BEHAVIOR OF REAL EMBANKMENTS. HOWEVER, IT SEEMS REASONABLE TO ASSUME THAT THE LONGITUDINAL EFFECTS OF THE EMBANKMENT LOADING ON ANY HORIZONTAL PLANE THROUGH THE EMBANKMENT OR FOUNDATION ARE ANALOGOUS TO THOSE DEMONSTRATED IN THE FIGURE FOR POISSON'S RATIO EQUAL TO ZERO. A HYPOTHESIS IS PRESENTED APPLYING THIS ANALOGY. REFERENCES: HORIZONTAL MOVEMENTS RELATED TO SUBSIDENCE, KENNETH L. LEE, C.K. CHEN, ASCE PROC. PAPER 6336, JANUARY 1969.

  • Supplemental Notes:
    • Vol 96 No SM1, PP 310-317, 1 TAB, 4 FIG, 9 REF
  • Authors:
    • Cappleman, H L
  • Publication Date: 1970-1

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  • Accession Number: 00235617
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Mar 25 1970 12:00AM