**4. Previous related studies**

Clay soils are important in the construction of buildings, dams, roads, airports, pavements and highways [25–34]. Soil problems encountered in geotechnical engineering need to be solved. Because of its double layer, clay can absorb water 10–500 times its own weight. In addition, it is considered to be a problematic soil that can show settlement under loading, with swelling or compression when it receives water. Karmi et al. [26] investigated two case studies of embankment dams in Iran. Researchers indicated that for large dams, the internal friction angle plays a more critical role in stability analyses than the cohesion parameter. Çabalar [28] investigated various fine contents and their effects on the triaxial behavior of coarse sand. Consequently, the high compressibility and other clay-like behaviors of mixtures were attributed to the particle characteristics (size and shape). Shanyoug et al. [31] investigated the effects of fine contents on the mechanical behavior of completely decomposed granite during dynamic compaction grouting. Consequently, researchers indicated that the compaction efficiency increases with the increasing fine content.

at different depths were largely influenced by the pore-size distributions, which vary in accor-

The Importance of Clay in Geotechnical Engineering http://dx.doi.org/10.5772/intechopen.75817 97

Dananaj et al. [46] investigated the microstructural formation and geotechnical properties of Ca-bentonite and Na-bentonite by XRD, chemical analysis and scanning electron microscopy (SEM). Researchers suggested that the differences in bentonite quality and smectite quantity influence the permeability. Dimitrova and Yanful [47] examined the factors affecting the shear strength of mine tailings. These researchers suggested that adding clay to mine tailings would cause a decrease in the frictional strength, but the magnitude of this decrease was greater when the clay was bentonite and lower when it was kaolinite. The stabilization of clays generally requires sand, lime, cement and fly ash as additive materials. Soil stabilization using additives comprises the oldest and most common method of soil improvement. Known applications date as far back as ancient Greek, Egyptian and Roman times [48]. In clayey soils, sand is preferred due to its ease of application and economy. Some researchers have observed clays with sand stabilization to investigate the mechanical and microstructural changes of the soils [49–56]. Other researchers have used chemical additives (lime, cement, fly ash and bitumen) in the stabilization of clayey soils [57–62]. Chemical stabilization may be the most economical and practical method of soil stabilization techniques, as well as for problematic soils under existing structures.

Al-Mukhtar et al. [61] examined the effect of the lime stabilizers on the geotechnical properties of highly plastic clay using microscopic data. These researchers suggested that the treatment of the expansive soil behavior in the geotechnical properties was primarily due to pozzolanic reaction. Al-Mukhtar et al. [62] examined lime consumption by 10% lime improvement, kaolinite, illite, smectite-kaolinite, smectite-illite and smectite, using X-ray diffraction and thermogravimetric tests. These researchers suggested that the amount of lime consumed during the short-term reaction varies from nothing for kaolinite to the maximum with sodiumsmectite. Khemissa and Mahamedi [63] examined improvement with a mixture of various ratios of cement and lime on expansive over-consolidated clay. These researchers observed an increase in soil strength and durability due to the reaction between the soil and additive materials. In chemical stabilization, cation exchanges, flocculation and agglomeration, carbonation reactions and pozzolanic reactions occur. The soil workability affects the cation exchange, flocculation and agglomeration mechanisms, and in addition, the bearing strength affects the

Also, clay is desirable in many cases due to its properties, which may be used to benefit a geotechnical engineer's design. Clay provides impermeability in fill dams, and waste landfill clay provides effective support in the form of gellable slurry for the untreated soils when excavated for pond water retention. Clay also becomes a binding material when it joins a

Geotechnical engineering is one of the most important parts of any kind of construction. No matter how well the superstructure is projected, there is no sense in beginning construction

dance with the degree of weathering.

carbonation reactions and pozzolanic reactions [64].

certain ratio to coarse-grained soils.

**5. Conclusions**

Naik et al. [32] investigated the settlement of an institutional building located in South Goa, India. This building developed cracks when the construction reached the beam level. Some foundations were located in unconsolidated filled ground, according the standard penetration test, and thus, differential settlement was observed in the foundations. Dafalla [34] investigated the cohesion and angle of internal friction for granular soils using the direct shear test for different clay contents and different moisture contents. Consequently, researchers observed a steep drop in both cohesion and angle of internal friction in a moist, clay-sand mixture when the clay content was high. In addition, many researchers have studied the geotechnical engineering behavior of clays and their microstructure [35–39]. Rajasekaran et al. [35] investigated the influence of lime and sodium hydroxide on the microchanges in two marine clays using scanning electron microscopy (SEM). These researchers suggested that the addition of lime and sodium hydroxide created an optimal pozzolanic reaction.

Horpibulsuk et al. [36] investigated the strength development and microstructural changes of stabilized, silty clay. SEM, mercury intrusion and thermal gravity analyses for qualitative and quantitative analyses of the sample microstructures were conducted in this research. Researchers suggested that the volume of large pores increased due to the presence of coarser particles in a short period, whereas the volume of small pores decreased due to the solidification of the hydrated cement. Some studies indicated that Atterberg's limits and grain-size distribution are indicators of the soil mineralogy and for the determination of many fine-grained soil properties [37–38]. Simultaneously, Atterberg's limits affect grain-size distribution and mineral composition. For example, an increase in the surface area is observed with increased liquid limits [37, 40–43]. Grabowska-Olszewska [44] investigated the relationship between the colloidal activity and the specific surface area of model soils of kaolinite and bentonite mixtures. Researchers observed that when the clay fraction increases, the total surface area also increases. Rahardjo et al. [45] investigated the index property and engineering property tests on residual soils from two major geological formations in Singapore. These researchers suggested that that the variations in the index and engineering properties of the residual soils at different depths were largely influenced by the pore-size distributions, which vary in accordance with the degree of weathering.

Dananaj et al. [46] investigated the microstructural formation and geotechnical properties of Ca-bentonite and Na-bentonite by XRD, chemical analysis and scanning electron microscopy (SEM). Researchers suggested that the differences in bentonite quality and smectite quantity influence the permeability. Dimitrova and Yanful [47] examined the factors affecting the shear strength of mine tailings. These researchers suggested that adding clay to mine tailings would cause a decrease in the frictional strength, but the magnitude of this decrease was greater when the clay was bentonite and lower when it was kaolinite. The stabilization of clays generally requires sand, lime, cement and fly ash as additive materials. Soil stabilization using additives comprises the oldest and most common method of soil improvement. Known applications date as far back as ancient Greek, Egyptian and Roman times [48]. In clayey soils, sand is preferred due to its ease of application and economy. Some researchers have observed clays with sand stabilization to investigate the mechanical and microstructural changes of the soils [49–56]. Other researchers have used chemical additives (lime, cement, fly ash and bitumen) in the stabilization of clayey soils [57–62]. Chemical stabilization may be the most economical and practical method of soil stabilization techniques, as well as for problematic soils under existing structures.

Al-Mukhtar et al. [61] examined the effect of the lime stabilizers on the geotechnical properties of highly plastic clay using microscopic data. These researchers suggested that the treatment of the expansive soil behavior in the geotechnical properties was primarily due to pozzolanic reaction. Al-Mukhtar et al. [62] examined lime consumption by 10% lime improvement, kaolinite, illite, smectite-kaolinite, smectite-illite and smectite, using X-ray diffraction and thermogravimetric tests. These researchers suggested that the amount of lime consumed during the short-term reaction varies from nothing for kaolinite to the maximum with sodiumsmectite. Khemissa and Mahamedi [63] examined improvement with a mixture of various ratios of cement and lime on expansive over-consolidated clay. These researchers observed an increase in soil strength and durability due to the reaction between the soil and additive materials. In chemical stabilization, cation exchanges, flocculation and agglomeration, carbonation reactions and pozzolanic reactions occur. The soil workability affects the cation exchange, flocculation and agglomeration mechanisms, and in addition, the bearing strength affects the carbonation reactions and pozzolanic reactions [64].

Also, clay is desirable in many cases due to its properties, which may be used to benefit a geotechnical engineer's design. Clay provides impermeability in fill dams, and waste landfill clay provides effective support in the form of gellable slurry for the untreated soils when excavated for pond water retention. Clay also becomes a binding material when it joins a certain ratio to coarse-grained soils.
