RUI: Development of a Textural Weathering Classification for Limestone Using Signal Processing Techniques

Weathering has a negative effect on the strength and stiffness of rock. When tunnels and foundations for buildings and bridges are designed to be supported by weathered rock, it is important to understand the magnitude of the decrease in strength and stiffness. Currently weathering is assessed using visual descriptions of rock specimens. Previous studies have shown it is very easy to visually distinguish unweathered and highly weathered specimens but specimens with intermediate weathering states are often misclassified. This award supports fundamental research to develop a measurement based weathering classification system for limestone rock specimens. The measurement based system will be more accurate than the visual based system and lead to more economical and sustainable designs of infrastructure supported by weathered rock. This work can also be utilized for the assessment of rock joint roughness which can lead to safer and more economical rock slopes. Therefore, results from this research will benefit the U.S. economy and society. This research involves undergraduate students in both civil and electrical engineering. The multi-disciplinary approach will help broaden participation of underrepresented groups in research and positively impact engineering education at the undergraduate level.

This work will develop the first quantifiable textural based weathering classification system for limestone rock specimens. The system will be based on the percentage and size of fossilized shells in the specimens, the micro-topography determined through surface characterization, and roughness values quantified using signal and image processing algorithms. Surface characterization will be performed using an industrial profiler, a three-dimensional laser scanner, and close range photogrammetry. Roughness is typically characterized using two-dimensional magnitude based algorithms. This work will incorporate frequency based algorithms and extend roughness assessment to three-dimensions. The weathering classification system will be based on the familiar Geological Strength Index system used for rock mass classification.