Abstract
Construction of major civil engineering works in the weatherable Piraeus marl, Greece, raised several questions focusing on its "rock-like" or its "soil-like" behaviour. The research in this paper presents a method of verifying the degradation mechanism of the marl due to assumed weathering processes. For this purpose, a large number of laboratory tests have been reevaluated using correlations between selected index properties of the material. It is shown that the Piraeus marl is controlled by the degree of solution of diagenetic calcite bonds. The remaining amount of calcite, probably infiltrating downwards, is the key factor over large variations in strength, deformability and dry density, and over minor variations in mineralogy and plasticity. On weathering, the marl has increased in voids and in water content, with a general reduction in the intensity of particle bonding, mainly in the upper 15m. In that zone, strength can be attributed mainly to the effects of overconsolidation. On a rock engineering basis, the Piraeus marl can be classified at best as a very low strength-low modulus ratio material.
