A laboratory study on weak high porosity outcrop chalk has been performed in order to see how mechanical strength is affected when the material is strained beyond the elastic limit. Both tensile and compressive strength and Young's modulus are considerably reduced, although there is some strain hardening in compressive strength with increasing degree of deformation.

A second part of the study addresses the possibility of causing damage when the pore pressure is increased like in stimulation operations. Samples that were pressurized, when locked in an oedometer cell, became weaker than samples with no pressure cycle.

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