Closure to “Vibration Modulus of Normally Consolidated Clay”

THE WRITERS ARE GRATEFUL TO WHITMAN, HOLT AND MURPHY, AND DOBRY AND POBLETE FOR DEMONSTRATING THE GOOD AGREEMENT BETWEEN VALUES OF THE SHEAR MODULUS CALCULATED IN THE PRESENTED EQUATION AND SHEAR WAVE VELOCITIES MEASURED IN THE FIELD BY GEOPHYSICAL METHODS AT TWO DIFFERENT SITES. TEST RESULTS SHOW THE EFFECT OF VOID RATIO, AMBIENT STRESS, STRESS HISTORY, FREQUENCY, AND STRAIN AMPLITUDE ON THE VIBRATION SHEAR MODULUS OF THESE UNDISTURBED SAMPLES. INDEX PROPERTIES IN THE CLASSIFICATION OF VARIOUS UNDISTURBED COHESIVE SOILS TESTED ARE PRESENTED IN A TABLE AND THEIR PARTICLE SIZE DISTRIBUTIONS SHOWN IN A FIGURE. THE VALUES OF VOID RATIO ARE PRESENTED IN A FIGURE. ANOTHER FIGURE PRESENTS THE EFFECT OF ISOTROPIC COMPONENTS OF STRESS ON UNDISTURBED SAMPLES. THE EFFECT OF OVERCONSOLIDATION RELATIONSHIPS ARE PRESENTED. WHITMAN, HOLT AND MURPHY HAVE PRESENTED A FIGURE SHOWING A CURVE BY WHICH THE MODULUS FOR HIGHER STRAIN AMPLITUDES MAY BE COMPUTED FROM THE MODULUS AT SMALL STRAIN AMPLITUDES. RESULTS ARE PRESENTED IN A FIGURE OF (1) COHESIVE SOIL AND (2) DRY SANDS WHICH WERE TESTED AT DIFFERENT FREQUENCIES AND NUMBERS OF CYCLES. DATA FOR BOTH HOLLOW AND SOLID CYLINDRICAL SPECIMENS SHOWED THE EFFECT OF THE VARIATION OF STRAIN WITHIN THE SPECIMEN TO BE SMALL. THIS IS ALSO TRUE FOR LARGE STRAIN AMPLITUDES PROVIDED THE MEASURED PARAMETERS ARE CORRELATED TO THE AVERAGE SHEAR STRAIN AMPLITUDE IN THE SPECIMEN. THE RESULTS FOR TWO SENSITIVE CLAYS ARE SHOWN IN A FIGURE. THE SPECIAL STRUCTURE OF HIGHLY SENSITIVE CLAYS APPEARS TO INCREASE THE MODULUS ABOVE THAT FOR LESS SENSITIVE SOILS WITH SIMILAR VOID RATIO AND STATE OF STRESS. REFERENCES: VIBRATION MODULUS OF NORMALLY CONSOLIDATED CLAY, BOBBY O. HARDIN, WILLIAM L. BLACK, ASCE PROCEEDINGS PAPER 5833, MARCH, 1968.