New weathering classification system of rocks based on the engineering properties

The purpose of this case study is to introduce a new weathering classification system of rocks based on the engineering properties. Even though several authors have suggested different classification systems worldwide, limited research has been conducted to propose a classification system that includes more than two engineering properties. To suggest a better system to classify the rock, four rock types belonging to different weathering grades were tested (around 150 tests) to determine the point load index ( I s (50) ), slake durability index ( I d2 ), density, mineralogy, and microstructure. The mineralogy and microstructure of fresh and weathered samples were observed by conducting X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests. The I s (50) , I d2 , and density appeared to decrease as weathering grade increased, albeit with relatively high correlation coefficient. The statistical analysis, including multiple linear regression, was used to identify the correlations between those parameters. The increase in clay mineral content, microcracks, and pore density was observed in the weathered samples when comparing to fresh samples. The obtained test results were used to develop engineering classification systems (ECS) which provide a quick estimation of engineering properties of the weathered rock. The proposed ECS are developed using the relevant published literature. Therefore, these classifications can be used generally to predict the engineering properties of basalt, argillite, sandstone, and greywacke.