Discussion of “An Analysis of Consolidation Theories”

MR. VIGGIANI SUGGESTS MODIFICATIONS TO THE AUTHOR'S COMPARISON WITH THE THEORY OF TERZAGHI-RENDULIC. THE EQUATIONS OF BIOT-MANDEL MUST BE CAST INTO A SLIGHTLY DIFFERENT FORM. THESE EQUATIONS ARE PRESENTED, WITH CORRESPONDING ONES OF TERZAGHI-RENDULIC. THE MAIN DIFFERENCE BETWEEN THE TWO THEORIES IS THAT BIOT-MANDEL MAKES ALLOWANCE FOR TOTAL STRESS CHANGES DURING CONSOLIDATION WHILE THE TERZAGHI-RENDULIC ASSUMPTION IS THAT TOTAL STRESSES ARE TIME-INDEPENDENT. MESSRS. DAVIS AND POULOS FEEL THAT THE METHOD OF PRESENTATION USED BY THE AUTHORS OVEREMPHASIZES THE DIFFERENCES BETWEEN THE APPROXIMATE DIFFUSION SOLUTION AND THE CORRECT BIOT SOLUTION IN REGARD TO PORE PRESSURES. THEY PRESENT A DIFFUSION-TYPE EQUATION CONSISTENT WITH THE BIOT THEORY FOR THREE-DIMENSIONAL CONDITIONS DERIVED BY GIBSON AND LUMB. IT IS SHOWN THAT UNDER REASONABLY LOGICAL INTERPRETATION, THE APPROXIMATE DIFFUSION THEORY IS CAPABLE OF PREDICTING CONSOLIDATION BEHAVIOR UNDER TWO- AND THREE-DIMENSIONAL STRAIN CONDITIONS WITH AN ACCURACY SUFFICIENT FOR ENGINEERING PURPOSES. REFERENCES: AN ANALYSIS OF CONSOLIDATION THEORIES, ROBERT L. SHIFFMAN, ALBERT T-F. CHEN, JANE C. JORDAN, ASCE PROC. PAPER 6370, JANUARY 1969.