Abstract: The Pliocene epoch mudstone in the XiheTianshui Section of Shitian Expressway in Gansu Province has the characteristics of newly geologically deposited, less degree of sedimentary and containing large amount of clay minerals so that this mudstone has the special engineering properties. This paper presents of the index, slaking, expansive and low strength properties of the mudstone and these properties provide the geotechnical bases for the design of roadways and structures in the area. The recommendations from this study can effectively reduce the geological related hazards induced by the adverse effect of mudstone.

Key words: Pliocene Epoch, Mudstone, Clay Minerals, Expansive Properties, Slaking