**1. Introduction**

Geotechnical engineering is a broad discipline consisting of soil mechanics and foundation engineering. Geotechnical engineering is also called geotechnique engineering or geomechanics. Geotechnical engineering addresses the application of engineering mechanics to soil and rock problems. The properties, behavior and performance of soils are addressed by engineering mechanics. Subsequently, the obtained data are processed and interpreted [1]. Geotechnical engineers consider landslides and earthquakes when planning and designing structures for buildings, roads, embankments and landfills. Geotechnical engineers also examine billions of years of geological history through soils. Therefore, examinations of the heterogeneous nature of soils require the resolution of complex problems. All types of

© 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. © 2018 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.

engineering structures such as residential buildings, service buildings, bridges, dams, roads and airports are located on or in the ground. As Richard said in 1995, "is supported by almost every construction ground or rocks. Unsupported are either fly or float or fall" [2]. Even when they are well designed, the safety of an engineering structure cannot be ensured when there is inadequate bearing capacity, high swelling/shrinking potential and settlement (compression) of the soil. For this reason, geotechnical applications in soils have become obligatory. Many studies were carried out in the 1910s due to the large number of landslides and docks that occurred in Sweden. The recommendations that resulted from these studies are now being applied as a landslide analysis method known as the Swedish slice method. With an increasing number of wall demolitions, Skempton presented calculations in 1979 [2]. Today, the latest technologies used in geotechnical soil applications are problematic for transportation power with the increase in industrialization and different kinds of construction.

Looking at the history of geotechnical engineering, Turkey is an important place. Karl von Terzaghi, who is the founder of geotechnical engineering or the father of soil mechanics, investigated Haliç clay in Turkey and laid the foundation of geotechnical science. In his investigations of a clay-rich ground, which is abundant today, Terzaghi managed to obtain clay samples from the Black Sea coast (Kilyos) with the assistance of two brave students who endured many difficulties, including bandits, and being 20 km from the nearest motorway. The clays in Terzaghi's study in 1925 are numbered II and IV in the book, which is entitled "Erdbau Mechanic." This book is accepted as the foundational document of modern soil mechanics. The mathematical formulation of clay consolidation under constant pressure over time was investigated in this book, and it was discovered that there may be an analogy between heat conduction and the damping of additional void water pressure. Thus, the "clay consolidation problem" has been solved in all its aspects. In 1925, the results of Terzaghi's research in Turkey were published in the book "Soil Physics Fundamentals of Soil Mechanics" by the Franz Deutick Publishing House in Vienna. This book is recognized by the World Society of Civil Engineers as the foundational document for modern ground engineering [3].

dams, slurry walls, airports and waste landfills, it becomes even more important to address. Clays generally have low strength, high compressibility and high volumetric changes. Because of clay's high plasticity, permeability, bearing capacity and settlement characteristics, it is a material that has been studied and is still being studied in geotechnical engineering. In this study, the characteristics of clay are discussed and its importance in geotechnical engineering practices is noted. This chapter is composed of five main sections. In the first section, the importance of clay in geotechnical engineering is presented. In Section 2, clay is defined and its properties are discussed. Section 3 presents the use of clay in geotechnical engineering practices. In Section 4, previous, related studies are summarized. Finally, in Section 5, the

The Importance of Clay in Geotechnical Engineering http://dx.doi.org/10.5772/intechopen.75817 85

Clay minerals are called secondary silicates, because they are formed from the weathering of primary rock-forming minerals. Clay minerals occur in small particle sizes (<0.002 mm) and are very fine grained and flake shaped; they are separated from sand, gravel and silt due to the negative electrical load on the crystal edges and positive electrical load on the face. Clay

subject of clay is summarized and conclusions from this chapter are provided.

**2. Clay definition and properties**

**2.1. Clay definition**

**Figure 1.** Pisa tower [2].

The first building which comes to mind regarding soil problems is the Pisa Tower. Its construction began in 1173 and took approximately 200 intermittent years to complete. The tower began to lean during construction and the leaning has continued after the construction was completed. In 1982, the hill was 58.4 m long and deviated by 5.6 m from the plumb (**Figure 1**). This soil problem is explained by clay soil settlement of up to 11 m from the surface [2]. The soils of interest in geotechnical engineering are formed from rock degradation. This process consists of physical and chemical weathering. Clay is largely composed of chemically altered and different materials of bedrock. The change in contents and structures due to physical, chemical and biological processes that occur in rocks is called weathering. Physical weathering is the mechanical disintegration of rocks by heat exchange and the effects from glaciers, waves and wind. Biological weathering results from the activities of plants and animals within a rock. Chemical weathering is caused by the effects of oxidation, reduction, hydrolysis, carbonation and organic acids in rocks. As a result of weathering, all kinds of soils are formed. In physical weathering, blocks of rock, gravel, sand and silt materials are formed, whereas clay minerals are formed by chemical weathering [4]. In geotechnical engineering practices, clay is generally seen as a problematic soil. When these soils are seen during the construction of road

**Figure 1.** Pisa tower [2].

engineering structures such as residential buildings, service buildings, bridges, dams, roads and airports are located on or in the ground. As Richard said in 1995, "is supported by almost every construction ground or rocks. Unsupported are either fly or float or fall" [2]. Even when they are well designed, the safety of an engineering structure cannot be ensured when there is inadequate bearing capacity, high swelling/shrinking potential and settlement (compression) of the soil. For this reason, geotechnical applications in soils have become obligatory. Many studies were carried out in the 1910s due to the large number of landslides and docks that occurred in Sweden. The recommendations that resulted from these studies are now being applied as a landslide analysis method known as the Swedish slice method. With an increasing number of wall demolitions, Skempton presented calculations in 1979 [2]. Today, the latest technologies used in geotechnical soil applications are problematic for transportation

Looking at the history of geotechnical engineering, Turkey is an important place. Karl von Terzaghi, who is the founder of geotechnical engineering or the father of soil mechanics, investigated Haliç clay in Turkey and laid the foundation of geotechnical science. In his investigations of a clay-rich ground, which is abundant today, Terzaghi managed to obtain clay samples from the Black Sea coast (Kilyos) with the assistance of two brave students who endured many difficulties, including bandits, and being 20 km from the nearest motorway. The clays in Terzaghi's study in 1925 are numbered II and IV in the book, which is entitled "Erdbau Mechanic." This book is accepted as the foundational document of modern soil mechanics. The mathematical formulation of clay consolidation under constant pressure over time was investigated in this book, and it was discovered that there may be an analogy between heat conduction and the damping of additional void water pressure. Thus, the "clay consolidation problem" has been solved in all its aspects. In 1925, the results of Terzaghi's research in Turkey were published in the book "Soil Physics Fundamentals of Soil Mechanics" by the Franz Deutick Publishing House in Vienna. This book is recognized by the World Society of Civil Engineers as the foundational document for modern ground engineering [3]. The first building which comes to mind regarding soil problems is the Pisa Tower. Its construction began in 1173 and took approximately 200 intermittent years to complete. The tower began to lean during construction and the leaning has continued after the construction was completed. In 1982, the hill was 58.4 m long and deviated by 5.6 m from the plumb (**Figure 1**). This soil problem is explained by clay soil settlement of up to 11 m from the surface [2]. The soils of interest in geotechnical engineering are formed from rock degradation. This process consists of physical and chemical weathering. Clay is largely composed of chemically altered and different materials of bedrock. The change in contents and structures due to physical, chemical and biological processes that occur in rocks is called weathering. Physical weathering is the mechanical disintegration of rocks by heat exchange and the effects from glaciers, waves and wind. Biological weathering results from the activities of plants and animals within a rock. Chemical weathering is caused by the effects of oxidation, reduction, hydrolysis, carbonation and organic acids in rocks. As a result of weathering, all kinds of soils are formed. In physical weathering, blocks of rock, gravel, sand and silt materials are formed, whereas clay minerals are formed by chemical weathering [4]. In geotechnical engineering practices, clay is generally seen as a problematic soil. When these soils are seen during the construction of road

power with the increase in industrialization and different kinds of construction.

84 Current Topics in the Utilization of Clay in Industrial and Medical Applications

dams, slurry walls, airports and waste landfills, it becomes even more important to address. Clays generally have low strength, high compressibility and high volumetric changes. Because of clay's high plasticity, permeability, bearing capacity and settlement characteristics, it is a material that has been studied and is still being studied in geotechnical engineering. In this study, the characteristics of clay are discussed and its importance in geotechnical engineering practices is noted. This chapter is composed of five main sections. In the first section, the importance of clay in geotechnical engineering is presented. In Section 2, clay is defined and its properties are discussed. Section 3 presents the use of clay in geotechnical engineering practices. In Section 4, previous, related studies are summarized. Finally, in Section 5, the subject of clay is summarized and conclusions from this chapter are provided.
