Water-Rock Interaction Mechanisms and Ageing Processes in Chalk - Advances in Data, Methods, Models and Their Applications in Geoscience - page 175

a) b)

c) d)
Fig. 13. a) and b) fracture opening in chalk specimen during drying, c) and d) fracture
closing following the second saturation

allow the quantification of the Young's modulus. The latter is clearly influenced by the
various states of saturation that follow; Young's modulus for dry chalk was E dry = 1.1 GPa, as
compared with that of saturated chalk, where E sat = 0.71 GPa. The ratio E dry / E sat = 1.6 is of
the same order as that obtained by other researchers by means of standard laboratory
unconfined compression tests (e.g. Raffoux & Ervel, 1980). At a suction level, s o , of 4.2 MPa
the value of Young's modulus, E o , is between E dry and E sat , with a value of 0.78 GPa.
In relation to material strength, the comparison between the unconfined compression
strength (UCS) values obtained at saturated and dry states gives a ratio UCS dry /UCS sat  2 in