For analytical and numerical calculations for the engineering feasibility assessment of a deep geological repository  for  disposal  of  nuclear  waste  in  the  Opalinus  Clay  and  its  maximum  depth  below  ground surface, NAGRA established geomechanical parameters that are based on a large number of laboratory test results. Results from uniaxial compression, triaxial compression and oedometer tests were used to quantify the effective strength properties, the undrained shear strength and both, drained and undrained elastic  properties  of  intact  Opalinus  Clay.  The  authors  of  this  report  were  commissioned  by  ENSI  to review and judge these geomechanical properties in terms of completeness and reliability.

This  review  report  addresses  the  conceptual  constitutive  framework  for  Opalinus  Clay  and  the simplifications  proposed  by  NAGRA,  provides  the  geomechanical  fundamentals  that  are  needed  to adequately judge the experiments on intact Opalinus Clay and their interpretation, and assesses in detail the various test series on intact Opalinus Clay utilized and interpreted by NAGRA.