PORE PRESSURE MEASUREMENTS DURING FREEZING OF AN OVERCONSOLIDATED CLAYEY SILT

Frost heave tests on overconsolidated clayey silt specimens have been conducted with and without applied back-pressure. Frost heave characte ristics are, at first approximation, independent upon the magnitude of applied back-pressure provided that the unfrozen soil remains saturat ed. For the soil studied the critical suction at which desaturation oc curs is about 40 kPa. Pore pressures were also measured in the unfroze n soil during freezing. The experimental results confirm steady state flow conditions in overconsolidated soil specimens even during the ear ly stage of freezing. However, suctions in excess of 100 kPa can be ge nerated at the frost front depending upon the freezing conditions. Thi s, in turn, may lead to desaturation of the unfrozen soil near the fro st front and render the analysis of a frost heave test even more compl ex. It is suggested to conduct frost heave test using a back-pressure equal to the hydrostatic pressure in the field and with a value of suc tion at the frost front close to that in the field in order to assess the relevant segregation potential.