[en] Because of the long design life, elevated temperatures, and the location at depth (high stresses), time-dependent aspects of the mechanical properties of crystalline rock are potentially important for the design and the long term safety of the radioactive waste repository at Olkiluoto. However, time-dependent effects in rock mechanics are still one of the least understood aspects of the physical behaviour of rock masses, this being partly due to the fact that it is difficult to conduct long-term experimental tests - either in the laboratory or in situ. Yet, the time-dependent mechanical behaviour needs to be characterised so that it can be included in the modelling studies supporting repository design. The Introduction explains the background to the literature survey and includes definitions of the terms 'creep' (increasing strain at constant stress) and 'stress relaxation' (decreasing stress at constant strain). Moreover, it is noted that the rock around an in situ excavation is loaded by the adjacent rock elements and so the timedependent behaviour will depend on the unloading stiffness of these and hence will not actually be either pure creep or pure stress relaxation. The Appendix contains the results of the literature survey of reported time-dependent research as it applies to crystalline rock. A summary of each of the 38 literature items is presented in tabular form covering document number, subject area, document reference, subject matter, objectives, methodology, highlighted figures, conclusions and comments. It is concluded that the time-dependent failure strength of all rocks observed may be interpreted by sub-critical crack growth assisted by the stress corrosion mechanism. Also, certain parameters are known to affect the long-term properties: mineralogy, grain size, water/water chemistry, confining stress and loading history. At some point in the loading history of rock, the state of crack development reaches a point whereby the continued generation of damage results in a magnified effect in terms of coalescence of propagating cracks and reduction in the cohesion of the rock. The combined effect of heat (produced by the high-level waste) and groundwater is assumed to accelerate the time-dependent behaviour of rock. The results of the long-term loading tests have shown that σ_cd (crack damage strength) may be a reasonable estimate of the long-term rock strength, particularly at low confinement. Several attemps have been made to model the long-term behaviour of rock. For example, using the PFC (Particle Flow Code) model, the strength degradation model was consistent with the mechanism of stress-corrosion in crystalline rock. The activation stress was found by calibrating the model to static fatigue test data and corresponded to approximately 60% of the laboratory compressive strength. (orig)