A STUDY OF SECONDARY CONSOLIDATION IN CLAYS

Abstract

An experimental study of secondary consolidation has been carried out for two plastic clays. Tests have con- firmed the quasi-preconsolidatipn behaviour of clays Lateral pressure was also measured in the consolidometer with the help of_ strain gauges fixed on the consolidometer ring. It was found that pressure during the process of secondary consolidation increases, sometime decreases with fluctuations and the cause for this behaviour of pressure is not yet known. Lo's method of plotting has been used o determine the value of secondary compressibility which may help in predicting secondary consolidation in the field. Merchant's Coeffi- cients M and N are also determined by knowing the secondary compressibility. The variation Of these coefficients with different increment ratio has also been determined from experimental tests. etrological study of soil showed that the structure of clay gets dispersed if the soil is subjected to long duration of secondary consolidation. A graphical method has been attempted to predict the total amount of the secondary consolidation in the laboratory on the basis of ultimate settle-ment. Crawford's method of plotting of time--settlement on log-log scale has not been found so satisfactory for separating primary consolidation from the secondary consolidation because of the very slow settlement compared to the long duration. Secondary compression has been reduced considerably by the use of Hydrogen Peroxide, Sodium Hexametaphosphate and Silicon grease.