Many uniaxial and diametrical compression tests have been performed by consecutively decreasing the moisture in the tertiary mudstone, the most typical of the “Nangan”, and the relation between the moisture content and the strength of the mudstone was examined. As a result of the test, it was found that the relation might be classified as coming under a change which systematically corresponds with the specified grouping system and its progress in the lithyfication process.
Moreover, since the internal friction angle is constant for the most part in the moisture content, it can be said that the cohesion giving the constituent grains the strength to bring about the change in the mudstone, has the greater influence on the strength change