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Frost-heave induced interaction between buried pipelines and soils

Jun Hu

1996/01

This thesis investigates the interaction between frozen soil and a pipeline embedded in a discontinuous frost heat zone. The computational modelling procedures proposed in the thesis include the modelling of frost heave generation, the constitutive modelling of the frozen soil, the structural behaviour of the pipeline and the constitutive modelling of the soil-pipeline interface. The interactive thermo-hydro-mechanical processes encountered in the problem are generally time-dependent and non-linear. The frost heave modelling utilizes the three-dimensional form of a modified hydrodynamic frost heave model. A finite element implementation of the model is used to estimate the frost heave in a one-dimensional element. The comparison of the numerical results with an experimental result indicates that the prediction by computational modelling can reasonably simulate observations of one-dimensional experiments. Two-dimensional and three-dimensional simulations also indicate that the numerical modelling can predict trends of frost heave development which are consistent with the localized cooling at the base of a cuboidal element. In the development of the interaction effects, the mechanical behaviour of the frozen soil is represented by a complete creep model. The proposed complete creep model can take into consideration all three creep processes associated with frozen soils. Computations have also been conducted to calibrate the predictions of the creep model with observed experimental data. Extensive computations have been performed to investigate the general creep responses of a variety of geotechnical structures. To examine frozen soil-pipeline interaction problems, the pipeline is modelled either as a Bernoulli-Euler beam or as a cylindrical shell which accommodates both flexural and shear stiffness effects. The numerical procedures are applied to examine the pipeline freezing experiment conducted at the large scale facility in Caen, France. The temperature profiles, soil heave, pipeline deformation and flexural moments developed in the pipeline due to the generation of frost heave in the discontinuous frost heave region are documented.

McGill University

Department of Civil Engineering and Applied Mechanics

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