On the high stress compression of Canadian oil sand

High stress oedometric compression tests (maximum 65 MPa) were carried out on samples of oil sand from Athabasca. X-Ray microtomography observation suggested that the initially dense interlocked grain fabric of the natural specimen has been altered by extraction, stress release, temperature change, storage, transport and sample trimming, resulting in a clearly apparent micro-crack network. Some time dependent effects that overestimated sample compressibility were observed when using the standard step loading procedures and a procedure with short steps (5 mn instead of 24 h) appeared to be better adapted. At low stresses, the sample disturbance appeared to overestimate the sand compressibility and it is suggested that better parameters could be obtained once submitting the sample to the maximum stress supported during its geological history (here 24 MPa). Grain crushing at high stresses was also evidenced and the role of grain crushing during the history of the deposit was also commented.