Characteristics of Crushed Rocks in a Landslide Body

—An Example of a Landslide Located in the Shimanto Belt—

Abstract

 Recently, observation of the detailed constituent geology and geological structure of landslide bodies has become possible by high-quality drilling techniques using surfactants. However, geological information was not obtained from high-quality drilled cores, and it was difficult to distinguish crushed rock due to landsliding and fault breccias. Therefore, detailed geological observations of the fault shear zones and high-quality cores drilled from a landslide body located in the Shimanto Belt, Kyushu, were performed. As a result, some planar fabrics were found in fault breccias around the landslide body, whereas random fabric were found in the breccias of the landslide body; therefore, randomly structured breccias may be an index for geological determining a landslide body. The difference between fault breccias having a planar fabric and a random fabric from the landslide body is attributed to the difference of confining pressure when each breccia was formed. Fault breccias were formed under high confining pressure, Whereas randomly structured breccias of a landslide body were formed under low confining pressure. When geological determining of a landslide body, it is important to classify the degree of crushing, to identify planar fabrics of the rocks and to identify position and frequency of random structured breccias.