Long-term stress-strain response of chalk: a micro-mechanical interpretation

A long-term laboratory test programme of conventional compression and extension tests was carried out with test durations from 8 to 22-months, in a purpose built environmentally controlled facility, with specially designed loading frames and modified triaxial cells. In addition, Scanning Electron Microscope (SEM) techniques were employed in an effort to investigate the micro-mechanical response. Creep strains appeared to trigger an ageing process that produces elevated post-creep strength and stiffness irrespective of the applied stress path.