Structure transitions of clay fills in North-Western Bohemia

Laboratory investigations of a clayey material from a fill created during open-cast coal mining are presented. Standard laboratory experiments (direct shear box, oedometer) have been supplemented by large scale testing. The mechanical behaviour of the fragmentary soil is influenced by the presence of macrovoids and shows further size and time effects, which makes the description of the clay fill behaviour difficult. The initially fragmentary structured soil changes with time back to a homogeneous material, due to weathering processes and through geostatic load. Partial saturation of the fragments also contributes to the peculiar behaviour of the clay fill material.