Proposed Classification of Degradable Muddy Rocks Using Physical and Chemical Properties

It is well known that muddy rocks such as mudstone and shale are susceptible to degradation over time, as symbolized by slaking, which can cause problems in the maintenance and management of earthwork structures such as cut slopes. In addition to the chemical properties of the clay minerals contained in the mudstone, which have been shown in many previous studies, the accelerated deterioration may be due to the effects of heavy rainfall, earthquakes, and stress release during and after construction. However, while there are cut slope faces with similar mudstone distribution that have achieved long-term stability without any measures, there are also cases in which the cut slopes have collapsed over time. Against this background, the authors have been conducting research on “classification of mudstone susceptible to deterioration using physical and chemical properties,” “effect of stress release on shear strength of mudstone discontinuities, “and” evaluation of the soundness of cut slope surfaces” for mudstones distributed in Miyazaki. This paper presents the physical and chemical properties and unconfined compression strength of mudstones, summarizes the relationships among them, and proposes a classification method of mudstones susceptible to degradation that reflects these results and discusses its usefulness.