Characterizing Clay Shales

Abstract

Clay shales are a group of clay mineral rich, poorly lithified materials that have strength properties that straddle this boundary. Clay shales may cover up to 35% of the earth's surface and engineering ventures such as dam and tunnel construction, highway embankments, coal and oil shale mining, and oil exploration have all encountered difficulties with clay shales. Clay shales are also the major contaminant removed from coal in wash plants. Other terms such as mudrock, clayrock, and compaction shale are equally valid. No definite term for these materials is available because of the ambiguities of such simple terms as clay, mud, shale, etc. The essential problem is that, depending on their composition and the engineering environment in which they occur, clay shales may behave either as a soil ora rock. The clay shale may degrade on exposure to the atmosphere and take on the nature of an engineering soil. If the shale remains intact, it may be that pore pressures can develop so that effective stresses must be considered.