Frost heave and clay expansion in freshwater clays

The clays under investigation are freshwater clays of high plasticity because of the up to 39% montmorillonite content, a swelling clay phase. The main mineral components are illite, up to 48%, dhlorite and kaolinite. Quartz, carbonates and feldspars are the non clay constituents. According to the high swelling phase part, the CEC is relatively high: between 24.9 and 58.5 meq/100 g. The exchangeable cations, the grain size distribution, the mineral content and the presence of a shallow groundwater table have a striking influence on the freeze-thaw process. Because of the special state of tension of the waterfilm surrounding the clay. flakes r . the. clay freezes, only below. -4°Cz The. evaluation of the first winter measuring period at our test site in the Austrian Molasse region (Miocene clays) shows surprisingly high frost heave of up to 60%. The ice heave is caused by ice lense formation. The natural moisture content of the clay was measured between 28 and 34%, which is water saturation, so that no clay expansion is to be expected. The high ice expansion is only possible if suction from the groundwater table is enabled. The cl ay below the frost penetration line experienced a slight shrinkage during the freezing periods. The laboratory data, gained from freezer tests, with simulation of field conditions, are in fairly good accordance with the field results.