Mineralogical and engineering properties of problematic expansive clayey beds causing landslides: Fid-Bau Portal

Mineralogical and engineering properties of problematic expansive clayey beds causing landslides

Al-Homoud, A. S. / Khoury, H. / Al-Omari, Y. A.

Abstract Many landslides have occurred at slope cuts-embankments adjacent to the Amman-Na'ur-Dead Sea and Irbid-Jerash-Amman highways in Jordan, especially during the last four years that were characterized by exceptional raifall during winter. Clayey beds found in the foundations of the failing areas were responsible for the occurrence of these landslides. This paper presents the results of research evaluating the chemical and engineering properties of the clayey beds in the Kurnub Sandstone Unit and the Ajlun Group of the Upper Cretaceous at twenty four landslide locations along the Amman-Na'ur-Dead Sea and Irbid-Jerash Amman highways. The clay minerals associated with the clayey beds were characterized and correlated with their engineering properties. The relationship between clay minerals, chemical and engineering properties of clayey beds and the foundation failures were also identified. The study included field visits to twenty four landslides sites to identify the problem, collect samples from the foundation along the slip surface, draw profiles and columnar sections. Chemical analysis was carried out for the whole rock sample and for clay samples. Tests were also conducted to evaluate the physical and engineering properties of the samples. Results showed that most of the landslides occurred within the upper part of the Kurnub Sandstone and the Na'ur formation. Quartz, calcite and dolomite are the non-clay minerals and Mixed-Layer (I/S) and kaolinite are the clay minerals identified for samples obtained from the studied areas. The jointed rocks allowed water to penetrate through the joints and reach the clayey beds. The ability of the mixed-layer (I/S) clays to expand in the presence of water resulted in the reduction of shear strength during rainfall, thus initiating the sliding process. The double-layer effect was noticed in samples with higher (I/S) content which gave the highest swelling potential, highest Liquid and Plastic Limits, and the lowest angle of friction.