PREDICTION OF THAW SETTLEMENT AND SURFACE ROUGHNESS FOR HIGHWAYS IN PERMAFROST AREAS

The design of highways in permafrost areas is based largely on empirical methods developed over many years of experience. Such methods produce suitable highways; however, the long term performance and maintenance costs are seldom balanced against initial capital costs. Methods of predicting thaw settlement and associated highway roughness are essential components of a pavement management system to balance these costs.; A thaw settlement model is developed in this thesis as one component of roughness prediction. Several methods of calculating permafrost thaw based on analytical approximations are described. A simplified method of calculating settlement based on instantaneous release of some frozen water became the basis of settlement estimation after thawing. A finite element computer program is developed to provide an estimate of thaw settlement and thermal modelling for a variety of pavement structures.; The thermal model is developed and verified using data obtained from an insulated embankment near Chitina, Alaska. The match between measured temperatures and simulated temperatures is shown to be very good.; A Markov modelling procedure was used to link thaw settlement obtained from the finite element program to highway roughness. Extensive roughness data for Mays Meter surveys in Alaska were obtained; however, the data for thaw settlement prediction was not sufficient for complete calibration of the Markov model.; A brief introduction to a Bayesian method of calibrating the Markov model using both measured and subjective data is also described. Bayesian statistics provides an alternative method of formalizing empirical data. This process could be used to calibrate the Markov model and update it as measurements become available.