Characterization and classification of tropical weathered shale in Ayer Hitam, Johor for excavation purposes

Abstract

Tropical weathered rocks exhibit a complex structure and difficult to be interpreted during earthwork excavation due to heterogeneity characteristics, degree of weathering, and structure formation. In fact, the weathering profile of problematic tropical sedimentary rocks of shale in Ayer Hitam, Johor is poorly understood and studied. This study aims to characterize and classify tropical weathered shale in Ayer Hitam, Johor based on qualitative and quantitative assessment for excavation purposes. An outcrop of weathered shale with inclined bedding of 30° to 50° located in Ayer Hitam, Johor was studied. The outcrop with 50 m length and 6 to 10 m high was divided into five sub-panels to map and classify the distribution of weathering grades based on the physical appearance and index properties. Point load test and jar slake index were conducted on various weathering grades. Result indicates the weathered shale profile in Ayer Hitam is an interbedded structure with various weathering grades of II, III, IV and V. The highest point load strength is 4.95 MPa recorded for grade II. The increase of weathering grade significantly decreased the point load strength up to 94.5% and shows reduction of jar slake value from index 2 to 6. The distribution grade of weathering of weathered shale profile in Ayer Hitam, Johor was successfully classified and mapped. The dominant weathering grades is highly and completely weathered (Grade IV and V), which can be used as a reference for excavation purposes.