To investigate the effect of water content on the mechanical behavior of fine-grained ‎sedimentary rocks three different types of shales; clayshale, mudshale and mudstone, from ‎different locations were studied. The samples were tested at different water contents ranging ‎from oven-dried to saturated condition. Preparing samples of standard size for testing was a ‎troublesome task. Many samples break during coring, cutting, grinding and storing because of ‎disintegration of these rocks when subject to change in water content. This nondurable ‎behavior of these rocks is responsible for numerous slope instability problems, underground ‎excavation problems and embankment failures.‎ Water content has been demonstrated to have a marked influence on the strength and ‎deformation properties. The uniaxial compressive strength and modulus of elasticity decrease ‎significantly as the water content increases. The results show a reduction of more than 90% in ‎uniaxial compressive strength from oven-dried to saturated condition. This strength reduction ‎due to moisture content for the rocks studied is significantly higher than the values reported ‎by other researchers. A general equation was developed for this type of fine-grained ‎sedimentary rocks that may be used for predicting uniaxial compressive strength from the ‎available information on water content.‎ ‎ ‎ Modulus of elasticity was found to be influenced by anisotropy, but the most significant ‎influence, regarding reduction of the modulus of elasticity, was the change from dry to ‎saturated condition. Test results show a significant reduction in the static modulus of ‎elasticity from oven-dried condition to saturated condition. The results of these tests show an ‎average reduction in modulus of elasticity, from that in dry state, of about 84% for the shales ‎studied. ‎

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