New Unified Classification for Fine Grained Sedimentary Material Based on Atterberg Limits Hakim Erlangga Bernado Sakti (a*), Sari Bahagiarti Kusumayudha (a), M. Nurcholis (b), Joko Soesilo (a), Andang Bachtiar (c)
a) Geological Engineering Department, Universitas Pembangunan Nasional ^Veteran^ Yogyakarta, Sleman, Indonesia
*hakimerlangga[at]gmail.com
b) Soil Science Department, Universitas Pembangunan Nasional ^Veteran^ Yogyakarta, Sleman, Indonesia
c) PT. Geosains Delta Andalan, Jakarta, Indonesia
Abstract
Fine grained sedimentary material, which comprises mud and mudrock is the most abundant sedimentary material. The term mud is used to describe grain sizes, including silt and clay. It is also used to refer to loose sedimentary material and soil. Mudrock is further divided into mudstone and shale based on structure, and into siltrock and clayrock based on grain size. However, the nomenclature of these materials is frequently inconsistent, and there is no unified classification system for these materials. This is due to the difficulty and expense of particle size analysis (PSA), particularly in silt and clay fractions. AIPEA and CMS have proposed using plasticity parameters, i.e., plasticity index (PI) and liquid limits (LL), to differentiate between silt and clay, with clay defined as a fine-grained material with PI greater than or equal to LL/2. In engineering geology, a quantitative limitation on mud and mudrock is necessary. This is defined as the uniaxial compressive strength (UCS) value, which is mudrock with a UCS > 1.2 MPa. Mudstone and shale can be distinguished based on the ease with which a fissility plane structure can be formed with a maximum thickness of 1 cm. The term shale is defined as a sedimentary rock that is easily fissile, whereas mudstone is defined as a rock that is not fissile (massive). This article presents a new unified classification for fine-grained sedimentary materials, including loose sediments, soils, and sedimentary rocks. This new unified classification is expected to facilitate the naming of fine-grained sedimentary materials and the determination of clay and silt fractions based on their plasticity, as an alternative to using PSA.
