**1. Introduction**

Complexity of large civil engineering projects such as dams necessitates extensive reconnaissance. Particularly, the construction of dams and reservoirs in karstified rocks with known high perviousness due to dissolution faults and conduits intensifies the risk of water loss and

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

instability [1]. Water seepage and loss through dam foundation and abutments, especially those constructed in karstic regions lead to considerable costs, sometimes postpones dam construction targets. Although this is of less importance regarding dam instability, current experience shows that there could be a fair relationship between instability and water seepage, where fault and fracture systems are the main conduits for water flow. Thus, the study of geological relationships is of major importance, with main emphasis on the characteristics of the structural features and recent tectonic movements [2]. The structural geology has a great deal in contributing to the engineering projects, and knowledge of structural geology setting is essential for safe design of these projects [3]. A detailed study with focus on the analysis of fault and fracture systems, their activities, movement types, and position ought to be done. The evaluation of stress relationships and possible temporal and spatial deformations are also necessary.

due to actively growing of structures [6]. In the Zagros fold belt, superimposed drainage was found to be related to structural associations leading to transverse drainage pattern [7]. The position of the folded structures had a decisive role in the formation of the pre-karstic drainage network, that is, directions of the main surface outflow. As a result of the new tectonic activity, the homogeneous anticlinal structure has been fractured transversely and huge separate blocks have been formed [8]. Accordingly, challenges regarding the relationship between geologic structure and dam behavior are described and discussed for four dam cases, namely Karun-1 concrete dam, Karun-3 concrete dam, Marun earth dam, and Gotvand earth dam,

Influence of Geological Structure on Dam Behavior and Case Studies

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The Zagros fold-thrust belt (briefly named as Zagros mountains) being located to the northeast of the Persian Gulf extends for about 1800 km between northern Iraq and the Strait of Hormuz and comprises the deformed part of the Arabian plate following its continental collision with central Iran almost since the Miocene [9]. It is a branch of the Alpine-Himalayan Orogenic belt [10, 11]. The mountain range can be divided into two distinct zones say, the northeastern High Zagros (**Figure 2**) and the southwestern Simply Folded Belt (SFB) based on topography, geomorphology, exposed stratigraphy, and seismicity [12]. The Simply Folded Belt extends from the High Zagros Fault to the Persian Gulf [13]. Topographic highs are typical of the anticlines and synclines form the topographic lows. The existing landforms graphically reveal the geologic structure. Anticlines show remarkable regularity in relief over long distances and the rivers which cut them usually do so at sharp angles to the strike of the anticlines. The SFB is a fold belt characterized by NW-SE trending parallel anticlines and synclines and is composed of elongated whaleback or box-shaped anticlinal mountains. From a geomorphological view point, the anticlines can be divided into two sets; plain anticlines and mountain anticlines [12].

which are located in Khuzestan Province, southwest of Iran (**Figure 1**).

**Figure 2.** Seismotectonic features of the study area in the Khuzestan Province [14].

**2. General geology and seismicity**

On a regional scale, structural relationships have an important role in forming the hydrogeological properties in karst regions. Although the possibility for karstification perpendicular to the geologic structures is considerably reduced, where an anticlinal structure exists between the reservoir and the lower erosion base level [4], in young orogens such as the Zagros belt, where transverse and antecedent drainage pattern is of particular importance [5], reservoir water tightness is highly risky due to dissolution fractures and conduits. One of the structural controls in the development of drainage in modern orogens is fault and fracture systems,

**Figure 1.** Locations of Karun-1 dam (1), Karun-3 dam (2), Marun dam (3), and Gotvand dam (4) considered for this study.

due to actively growing of structures [6]. In the Zagros fold belt, superimposed drainage was found to be related to structural associations leading to transverse drainage pattern [7]. The position of the folded structures had a decisive role in the formation of the pre-karstic drainage network, that is, directions of the main surface outflow. As a result of the new tectonic activity, the homogeneous anticlinal structure has been fractured transversely and huge separate blocks have been formed [8]. Accordingly, challenges regarding the relationship between geologic structure and dam behavior are described and discussed for four dam cases, namely Karun-1 concrete dam, Karun-3 concrete dam, Marun earth dam, and Gotvand earth dam, which are located in Khuzestan Province, southwest of Iran (**Figure 1**).
