STABILITY AND STIFFNESS OF CELLULAR COFFERDAMS

PAST EXPERIENCES WITH CELLULAR COFFERDAMS ARE DISCUSSED, PARTICULARLY THE DEFLECTION OF THE CREST OF COFFERDAMS, AND THE PERMEABILITY OF THE SHEET-PILE ENCLOSURES. CURRENT METHODS FOR DESIGNING CELLULAR COFFERDAMS ON ROCK, SAND, AND CLAY FOUNDATIONS ARE REVIEWED. THIS SURVEY SHOWS THAT THEORIES ON WHICH THE DESIGN OF THESE COFFERDAMS IS USUALLY BASED GIVE THE DESIGNER AN ADEQUATE CONCEPTION OF THE FACTORS THAT DETERMINE THE STABILITY OF COFFERDAMS. DISCUSSION IS LIMITED TO CELLULAR COFFERDAMS WHOSE CELLS ARE FILLED WITH SAND OR SAND AND GRAVEL. THE TRADITIONAL ASSUMPTION THAT A CELLULAR COFFERDAM CAN BE REGARDED AS A GRAVITY WALL LEADS TO ERRONEOUS CONCLUSIONS REGARDING THE DISTRIBUTION OF THE SOIL PRESSURE ON THE BASE OF THE DAM. IT IS CONCLUDED THAT THE LOCK FRICTION IN THE CROSS-WALLS ADDS MATERIALLY TO THE STABILITY OF THE COFFERDAM, AND IT REDUCES VERY CONSIDERABLY THE DEFLECTION OF THE CREST. THE REQUIRED DEPTH OF PENETRATION OF THE SHEET-PILES OF COFFERDAMS IS DETERMINED BY THE CONDITION THAT THE BEARING CAPACITY OF THE SHEET- PILES PER UNIT OF WIDTH SHOULD BE EQUAL AT LEAST TO 1.5 TIMES THE SHEARING FORCE WHICH ACTS PER UNIT OF WIDTH BETWEEN THE FILL AND THE LENGTH ROWS OF SHEET-PILES AT MAXIMUM OVERTURNING MOMENT. CELLULAR COFFERDAMS ON A SAND FOUNDATION REQUIRE, IN ADDITION TO ADEQUATE SHEET-PILE PENETRATION, A PROTECTION AGAINST THE FORMATION OF BOILS. THE PRINCIPAL DIMENSIONS OF CELLULAR COFFERDAMS ON STIFF CLAY CAN BE DETERMINED BY MEANS OF SEMI-EMPIRICAL EQUATIONS THAT ARE PROPOSED FOR THE DESIGN OF CELLULAR COFFERDAMS ON A ROCK FOUNDATION. THE DEGREE OF STABILITY OF THE COFFERDAM IS PRACTICALLY INDEPENDENT OF THE STRENGTH OF THE FILL IN THE CELLS. THE SHEARING RESISTANCE ON VERTICAL SECTIONS THROUGH THE FILL IN THE CELLS AND THE LOCK FRICTION CAN ONLY BE ESTIMATED. THEREFORE, THE PRINCIPAL SOURCES FOR INCREASED KNOWLEDGE ON CELLULAR COFFERDAMS ARE ACCURATE FIELD OBSERVATIONS.

  • Supplemental Notes:
    • Vol 110, PaPER 2253, PP 1083-1202, 39 FIG, 5 TAB, 45 REF,
  • Authors:
    • Terzaghi, K
  • Publication Date: 1945

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  • Accession Number: 00234432
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 5 1994 12:00AM