Experimental design for a pilot study on bedrock weathering near the permafrost table

An experimental design is described to test the hypothesis that ice segregation near the top of permafrost and in the lower part of the active layer can brecciate frost-susceptible bedrock. Seasonal temperature cycles in the active layer and the top of permafrost were simulated to a first approximation within a block of chalk measuring 30 m × 31 m wide and 33 m high and insulated around the sides to minimize lateral heat transfer. The block, moistened first by capillary rise, was initially frozen from the surface downwards, simulating permafrost aggradation. Thereafter, the upper half of the block was cycled above and below 0°C (simulating seasonal freezing and thawing of the active layer) while the lower half remained below 0°C (simulating permafrost). During thaw cycles water was supplied to the surface and base of the simulated active layer. Temperature, unfrozen water content, surface frost heave and porewater pressure within the chalk were monitored during the experiment.