In this thesis work to improve the Transport and Road Research Laboratory (TRRL) frost heave test is described along with a new indirect method of predicting the frost susceptibility of granular material. To determine the optimum TRRL test conditions temperatures in the Nottingham University cold room and prototype Self Refrigerated Unit (SRU) were automatically monitored. In a typical trial several thousand temperatures were recorded. These were reduced to just three independent parameters, each of which quantified a particular feature of the temperature regime. Temperature fluctuations in the water bath of the prototype SRU were excessive and so an improved Mk3 unit was developed . Road sub-base aggregates covering a wide variety of geological types and grading were tested. These had the same heave after 250 hours freezing in the Mk3 SRU and the cold room, at least within the working range. Rigorous statistical analyses revealed that frost susceptibility could be judged with equal precision after only 96 hours freezing. The variability of heave was the same in both units. This variability was attributed to intrinsic differences between nominally similar specimens. It is intended that a 96 hour Mk3 SRU, frost heave test will be specified in a new British Standard. The indirect method is based on the suction/moisture content characteristics of granular soils. These were determined using the osmotic suction technique although the specimen preparation procedure had to be improved to accommodate the hard, coarse aggregates. For all the materials tested, the volumetric moisture content at suction of pF2.5 (ϴ2.5) was strongly correlated with heave in the TRRL test. Calculations revealed that, for the TRRL test conditions, pF2.5 is a suction which must occur in the zone between the terminal ice lens and the limit of ice penetration. It is thought that ϴ2.5 reflects the overall permeability of this frozen fringe.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Nottingham University.