Effects of the Soft Rock Pre-consolidation on Time-dependent Deformations around the Tunnel Excavation

Original scientific paper Time-dependent deformations in soft rocks represent an important part of total deformations which occur after excavation of the tunnel opening. In the light of this, comprehensive laboratory uniaxial creep tests were performed on marl rock monolits. The testing used marl as a chosen representative rock samples of the group of soft rocks which exhibits creep behaviour. Analysis of test records of total and time-dependent deformations in initially nonpreconsolidated and pre-consolidated samples indicates differences in the magnitude of total deformation and the shape of recorded creep curve. A limited experimental evidence is argument in favor of the thesis that the primary creep is actually a delayed elastic deformation that is not significantly affected by the pre-consolidation stress history. Phenomenology of behavior identified in the tested marl samples can be associated with the records of the convergence measurements on a tunnel contour being excavated in soft rocks.