CLOSURE ON ANALYSIS OF SOIL LIQUEFACTION: NIIGATA EARTHQUAKE

AN ARBITRARY CHOICE OF BASE MOTIONS WAS NOT MADE IN SELECTING THE RECORD OBTAINED AT TAFT AS THE BASE ROCK MOTION AT NIIGATA. THE CHOICE OF THIS RECORD AS A REASONABLE ESTIMATE OF THE BASE ROCK MOTION AT NIIGATA IS IN ACCORDANCE WITH RECOGNIZED SEISMOLOGICAL MEASUREMENTS AND OBSERVATIONS. THE NUMERICAL CORRELATION OF RELATIVE DENSITY TO STANDARD PENETRATION RESISTANCE MISTAKENLY ATTRIBUTED TO TERZAGHI AND PECK WAS ACTUALLY THAT REPORTED BY GIBBS AND HOLTZ, WHO PRESUMABLY ASSIGNED THE NUMERICAL VALUES TO THIS CORRELATION. DONOVAN SUGGESTED THAT A SUBSTANTIALLY LOWER DAMPING RATIO SHOULD HAVE BEEN USED. HOWEVER, HIS ESTIMATE OF THE DAMPING RATIO WAS BASED ON DATA FOR SATURATED CLAYS. AVAILABLE TEST DATA FOR BOTH CLAYS AND SANDS INDICATE THAT SANDS HAVE HIGHER DAMPING RATIOS THAN DO CLAYS UNDER THE SAME AVERAGE CYCLIC SHEAR STRAIN. SEVERAL APPROXIMATIONS HAD TO BE MADE BECAUSE OF LIMITED AVAILABLE DATA CONCERNING THE VARIOUS FACTORS INCORPORATED IN THE ANALYSES. THE GREATEST UNCERTAINTY EXISTED REGARDING THE MODULUS VALUES FOR SANDS AND THE ACCURACY WITH WHICH CYCLIC LOADING TRIAXIAL COMPRESSION TEST DATA WERE REPRESENTATIVE OF THE BEHAVIOR OF SOIL UNDER THE STRESS CONDITIONS DEVELOPED IN THE FIELD. IT HAS BEEN FOUND THAT BOTH THE DYNAMIC MODULI AND DAMPING RATIOS OF SOILS VARY WITH THE MAGNITUDE OF THE STRAINS TO WHICH THE SOIL IS SUBJECTED. THESE VARIATIONS HAVE BEEN ASCERTAINED FROM THE RESULTS OF VIBRATORY AND CYCLIC LOADING TESTS PERFORMED ON REPRESENTATIVE SAMPLES OF DIFFERENT SOILS. DATA ARE PRESENTED ON MODULI AND DAMPING RATIOS FOR MEDIUM SANDS RELATIVE DENSITY 75%. AN EQUIVALENT LINEAR ELASTIC LUMPED-MASS SOLUTION WAS USED TO CHOOSE APPROPRIATE MODULI AND DAMPING RATIOS THAT ARE COMPATIBLE WITH THE AVERAGE STRAINS DEVELOPED. THE SAND PROFILES IN BOTH THE HEAVY DAMAGE AND LIGHT DAMAGE ZONES WERE REANALYZED USING THIS METHOD OF ANALYSIS. EACH OF THESE PROFILES WAS SUBJECTED TO THE BASE MOTION AND THE TIME HISTORIES OF SHEAR STRESS AT VARIOUS DEPTHS WITHIN THE PROFILE WERE DETERMINED. THE METHOD OF CALCULATING THESE TIME HISTORIES AND THE FINAL STEP IN ASSESSING THE LIQUEFACATION POTENTIAL ARE PRESENTED. REFERENCES: ANALYSIS OF SOIL LIQUEFACATION: NIIGATA EARTHQUAKE, H. B. SEED, I. M. IDRISS, JOURNAL OF THE SOIL MECHANICS AND FOUNDATIONS DIVISION, PROCEEDINGS OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS, PROCEEDINGS PAPER 5233, MAY 1967.

  • Supplemental Notes:
    • Vol 94, No SM 6, PP 1367-1371, 2 TAB, 2 FIG, 3 REF, APP
  • Authors:
    • Seed, H B
    • Idriss, I M
  • Publication Date: 1968-11

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  • Accession Number: 00235431
  • Record Type: Publication
  • Files: TRIS
  • Created Date: May 5 1994 12:00AM