The scope of the paper encompasses planar and compound sliding motions, which may exhibit creeping behaviour during a certain period but may evolve to a very rapid motion. Thermo-mechanical interactions, at the scale of the sliding surface, are accepted as a critical aspect to explain these motion phases and their relationship. The sliding kinetics and global equilibrium are described at a large scale and the evolving shearing strength at the sliding surface derives from the local analysis of the shearing band and its vicinity. Pore pressures, temperatures and related variables are calculated by resolving a set of balance equations. The paper describes the transition from creeping motions to a rapid event. Results are found in terms of dimensionless numbers. Calculation of the slide evolution requires special numerical techniques described in the paper. Band permeability is found to be the dominant property controlling the triggering of fast motions. The creeping stage and the eventual slide blow-up are intimately linked. This relationship is explored in the paper. The models presented can be readily used to back-analyse relevant case histories or, in principle, even to carry out predictive modelling, provided an adequate calibration is available for the material parameters.

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