STUDIES OF SWELL AND SWELL PRESSURE CHARACTERISTICS OF COMPACTED CLAYS

FACTORS AFFECTING THE VALUES OF SWELL AND SWELL PRESSURE DEVELOPED BY COMPACTED SAMPLES OF AN EXPANSIVE SOIL ON EXPOSURE TO WATER UNDER CONTROLLED CONDITION ARE EXAMINED. DATA ARE PRESENTED AND DISCUSSED TO ILLUSTRATE SUCH FACTORS AS: (1) THE EFFECT OF TIME ON SWELL PRESSURE. IT IS SHOWN THAT CONSIDERABLE PERIODS OF TIME ARE REQUIRED BEFORE A SAMPLE DEVELOPS ITS FULL SWELL PRESSURE AFTER EXPOSURE TO WATER, (2) THE EFFECT OF SAMPLE SHAPE ON MEASURED SWELL PRESSURES. IT IS SHOWN THAT SAMPLE FACES MUST BE PERFECTLY PLAIN IF RELIABLE MEASUREMENTS ARE TO BE MADE, (3) THE EFFECT OF VOLUME CHANGE ON MEASURED SWELL PRESSURES. IT IS DEMONSTRATED THAT VOLUME EXPANSIONS OF AS LITTLE AS 0.1 PERCENT DURING SWELL PRESSURE MEASUREMENT MAY CAUSE AN ERROR OF LARGE MAGNITUDE IN THE VALUES OF SWELL PRESSURE OBSERVED, (4) THE RELATION BETWEEN SOIL STRUCTURE, AS DETERMINED BY COMPACTION METHOD, AND THE AMOUNT OF SWELL AND THE SWELL PRESSURE, (5) THE EFFECT OF STRESS HISTORY ON SWELL AND SWELL PRESSURE, AND (6) THE RELATIONSHIP BETWEEN SWELL AND SWELL PRESSURE. IT IS SHOWN THAT THE MAGNITUDE OF THE SWELL PRESSURE CANNOT BE RELIABLY PREDICTED FROM A KNOWLEDGE OF THE AMOUNT OF SWELL. EXPLANATION OF THE RESULTS IS OFFERED, WHERE POSSIBLE, IN TERMS OF THE FUNDAMENTAL ASPECTS OF THE SYSTEM COMPOSITION AND STRUCTURE. PRACTICAL IMPLICATIONS OF THE RESULTS ARE POINTED OUT WITH PARTICULAR REFERENCE TO PAVEMENT DESIGN. /AUTHOR/