Abstract
The subway (metro) and tunnel excavation works are of high demand in today's large and urban cities. The use of tunnel boring machines resulted in huge quantities of crushed rock powder and generally treated as waste. This work is aimed at the characterization and assessment of Riyadh limestone powder and its possible use as a construction material. The environmental application of this powder as an additive to clay sand liners proved to be useful and efficient. Advanced testing indicated that this material can occupy part of the voids and help in reducing the high expansive nature of the liners and yet maintain a satisfactory hydraulic conductivity. Geotechnical characterization as well as SEM testing was performed. Soil water characteristic curves were established for selected mixtures. The introduction of this material was found environmentally friendly and can reduce the demand for bentonite and highly expansive additives.