Frictional and Hydraulic Behaviour of Carbonate Fault Gouge During Fault Reactivation - An Experimental Study

We presents results from an experimental program designed to shed light on the effect of stress and deformation history on the permeability and slip behaviour of faults in carbonate rocks. We investigate the mechanical and hydraulic behaviour of experimentally created fault cores and damage zones in natural travertine rock samples and also explore the role of a sealing layer on the frictional and hydraulic response of the rock. Following direct shear testing on the blocks, cylindrical plugs with diameter of 38mm were drilled across the slip surface to be tested in a conventional triaxial configuration monitoring the permeability and frictional behaviour of the samples. The results indicate that the fault cross cutting the sample is acting as seal and its permeability is negatively affected by an increase in mean effective stress; slip on the fault plane does not improve the permeability of the fault. It can be therefore concluded that leakage along an un-cemented carbonate gouge cannot be achieved by movement on the fault plane alone, at least not within the range of slip measureable with our apparatus (; other mechanisms (e.g. cementation of the gouge) need to be explored to assess the possible leaking scenarios in faulted carbonate rocks.