Sedimentological model for underground tigris terraces channel in Sallahuddin Oil Refinery, Beji, Iraq

The study area is located structurally southwest Makhulplunge. Quaternary deposits overlying unconformably Fat'ha and Injanah Formations. The Quaternary deposits beneath Sallahuddin oil refinery display topsoil and the third stage of Tigris river terraces. The latter is represented by braided to meandering river channels composed of; conglomerates, sandstones, and siltyclaystones. The conglomerate reflects channel deposits and longitudinal bars, whereas the sandstones and siltyclaystones represent the channel levee with occasional crevasses play. From the available data of 81 boreholes and vertical pits and trenches, a depositional model was built for the main and subsidiary channels, the water flows during flood times only due to its relatively higher altitude compared with the main channel. During groundwater levels rise due to pipe leakage of industrial acid water and the infiltration of the surface runoff water, the foundations of the civil and industrial buildings of oil refinery could be affected. In conclusion, this impact will change the lithology by the dissolution of the cementing materials of the conglomerates and hence, the geotechnical characteristics of the conglomerate and other lithology will decline to result in building foundation disturbances.