1 Introduction
1.1 Previous Studies
2 Materials and Methods
3 Necessary Steps in Geological Investigation
- To correct the drilling depths of the penetrated rocks.
- To indicated the mechanical properties of the penetrated rocks.
- To indicate cavities, voids, fractured and/or sheared zones in the borehole.
4 Mosul Dam: A Case Study
4.1 History of Mosul Dam Project
4.2 Details of Mosul Dam
4.3 Geology of the Mosul Dam Site
- Pila Spi Formation (Late Eocene): small outcrops of the Pila Spi Formation are exposed in the extreme northwestern side of the reservoir (Fig. 6). The formation consists of well bedded, dolomite, dolomitic limestone, limestone and rare marl. The exposed thickness of the formation is few meters only.
- Euphrates Formation (Early Miocene): the Euphrates Formation is exposed in the core of some anticlines in the reservoir area (Fig. 6), as well in the foundations of the dam. The formation consists of well bedded, hard limestone, marly limestone and dolomitic limestone. Some of the limestone beds are karstified as indicated by the presence of sinkholes. The thickness of the formation in nearby areas ranges from (15–50) m.
- Jeribe Formation (Middle Miocene): the Jeribe Formation is not recorded to be exposed in the dam site and reservoir area. However, the formation is recorded in the foundations of the dam (Sissakian et al. 2014). The formation consists of well bedded, hard limestone. The thickness in near surroundings is about 60 m.
- Fatha Formation (Middle Miocene): the Fatha Formation is widely exposed in the dam site and reservoir area (Fig. 6). The formation is characterized by cyclic sediments, the thickness of the formation is variable; in Butmah is 392 m, in Ain Zala 325. The formation consists of two members; these are:
- Lower Member the Lower Member consists of cyclic sediments, each cycle consists of green marl, limestone and gypsum. The abutments of the dam are located within this member. The rocks of this member are highly karstified, not only in the dam site and the reservoir area, but else-where in Iraq.
- Upper Member the Upper Member consists of cyclic sediments, each cycle consists of green marl, red claystone limestone and gypsum; in the uppermost part reddish brown sandstone is present. This member covers majority of the reservoir area.
- Injana Formation (Late Miocene): the Injana Formation is exposed in the eastern, northeastern and some parts of the northern banks of the reservoir (Fig. 6). The formation consists of fining upwards cyclic sediments of reddish brown sandstone, siltstone and claystone. The thickness of the formation is variable ranges from (200–330) m.
- Mukdadiya Formation (Late Miocene–Pliocene): the Mukdadiya Formation is exposed in the eastern bank of the reservoir (Fig. 6). The formation consists of fining upwards cyclic sediments of grey sandstone, siltstone and claystone; some of the sandstone beds are pebbly. The thickness of the formation is variable ranges from (100–230) m.