Rockfilling in Selahaddin Project and its long term stability control

The thesis study covers theoretical background and erection of a rockfill design in Salahaddin Mountain crossing highway. The superiority of limestone fill against the fill material borrowed from other rock types is due to its chief mineral which is calcite (CaCO3). Calcite is a soluble salt and it is mobile in moisture, precipitates in voids upon drying, and acts as mineral cement yielding rock with time. The rockfill under concern is adjacent to the deep portal excavation in limestone and volume of the excavated limestone is greater than that of designed rockfill. Moreover the upstream catchment area is barren and comprises highly pervious limestone whereas downstream of the rockfill consists of impervious clayey sedimentary rock unit. Consequently the specially designed limestone rockfill with clay core replaced the viaduct and acts as a groundwater recharge dam with spillway/underpass. The piezometric level in the existing deep wells at downstream area rose up around 100 m following the first wet period after the completion of the rockfill with 5 m wide dyke of clay core. Thus the project gained a rockfill of limestone, which turns into rock with time and a groundwater recharge dam instead of 1 km long viaduct. The prevailing various geological conditions along the project under concern forced the designer to suggest a new approach to classify earthfills and rockfills. In any case a rockfill is superior to earthfill if the material is borrowed from the same type of geological source. Calcareous rock sources are always preferable.