Petrographical and Geomechanical Properties of the Lower Oligocene Limestones from Al Ain City, United Arab Emirates

The Lower Oligocene limestones comprise most of the foundational bedrock of Al Ain city, situated in the south eastern part of the UAE. The limestone outcrops south of the city are folded, dissected by several sets of joints, and host abundant connected paleokarstic cavities of varied sizes. For this study, a number of rock samples were collected from different localities in the Lower Oligocene-aged rock units, for testing and analysis. The rocks are composed mainly of calcite with minor amounts of dolomite, quartz and clay minerals. The studied rocks have been affected by diagenetic processes including dissolution, dolomitization, compaction and cementation that partially control the mechanical behavior of the rocks. Investigating the physical and mechanical properties of the Lower Oligocene limestones lying at the foundation level beneath Al Ain city is an important step in dealing with the problem of foundation instabilities which have been reported in some parts of the city. The study clearly demonstrates the relation between lithologic properties and their corresponding strength. It revealed that dolomatization of limestones increases their strength, in contrary increasing the chalk percent decreases rock's strength. Consequently, there is a need to carefully categorize the local limestone rock properties as assistance to future infrastructural developments.