Shear Strength Of Weathered Soft Rock – Proposal of Test Method Additions

One of the main soft (weak, clay-bearing) rocks characteristic is relatively rapid deterioration and degradation of strength when soft rock is exposed to atmospheric agents (i.e. weathering). In the investigation of strength degradation caused with weathering, wetting – drying process as a part of weathering, can cause problems even with preparation of samples for testing. In contact with water, moisture of the material is changed and deterioration process is initiated. In order to overcome problem with sample preparation, additions to test procedure are proposed. Additions are tested on marl samples from Eocene flysch formation. Before immersion into the plaster for testing, samples were covered with a thin metal net and subjected to weathering. Purpose of the net is to hold sample as one unit, because during the weathering sample break into smaller peaces. Weathering of samples was simulated with wetting-drying process in laboratory conditions. Acquired results on weathered samples are compared with shear strength of unweathered samples.