SOIL TYPE INVESTIGATION OF THE DOĞANHİSAR CLAYS, CENTRAL ANATOLIA, TURKEY. İ.İnce* and A. Özdemir

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1 Ozean Journal of Applied Sciences 3(3), 2010 ISSN Ozean Publication SOIL TYPE INVESTIGATION OF THE DOĞANHİSAR CLAYS, CENTRAL ANATOLIA, TURKEY İ.İnce* and A. Özdemir Department of Geological Engineering, Selçuk University, Turkey * address for correspondence: Abstract: In this study, soil types of the clays knows as Doğanhisar clays located southeast of Doğanhisar (Central Anatolia) has been investigated. With this objective in mind, the clay samples collected from the Doğanhisar clay pit situated within the Ayaslar Formation have been analyzed at laboratory conditions in accordance with the specifications of TSE Following the experiments, soil properties such as grain sizes, Atterberg consistency limits, unit weights and activities have been ascertained. Afterwards, the soil type of the Doğanhisar clays was determined and compared by using the obtained index parameters and Casagrande and Polidori plasticity charts. It has been found out that the soil type in the Doğanhisar clay would be classified as CL type and ML types soil based on Casagrande and Polidori plasticity charts, respectively. Keywords: Doğanhisar clay pit, Casagrande plasticity chart, Polidori plasticity chart, Clay, Ayaslar Formation INTRODUCTION The classification of soil types is important by using the data obtained from the soil analyses as well as establishing a communicative language connecting the engineers from the field. Establishment of a common language in this subject facilitates the flow of information, experience transfer and interdisciplinary communication among various fields of engineering. Although the classification of the soil type is an insufficient criterion on its own, it is significant with respect to the estimation of the earth s behavior during construction operations and also under structural loads (Holtz and Kovacs, 2002). In this study, it has been aimed to identify the soil types of the 5 separate clay samples collected from different levels of the surface mined Doğanhisar clay pit formed in the Ayaslar Formation, which is located to the south of Ayaslar town (Figure 1). Grain size analysis (sieve analysis, hydrometer analysis) and consistency limit tests (liquid limit, plastic limit, shrinkage limit) have been conducted on the samples collected. In addition to these analyses, material properties such as specific weight, void ratio, porosity, degree of saturation etc. have also been measured. As a result, the soil type has been identified from the calculated index values. Two distinct types of plasticity charts (Casagrande s and Polidori s) have been used in order to specify the soil type and conduct comparisons. 357

2 Figure 1: Location map of the study area. GENERAL GEOLOGY The Ayaslar Formationis one of the widely exposed formation in the study area. The Miocene age this formation had originally been named by Umut et al. (1987). The formation displays unconformably over lies the Paleozoic basement rocks. It is compared of red conglomerate, conglomeratic sandstone, mudstone and claystone (İnce, 2004; Aksoy et al., 2008). It is overlain by the Doğanhisar Formation with angular unconformity (Umut et al., 1987; İnce, 2004). MATERIAL AND METHODOLOGY Disturbed and undisturbed samples were collected to determine the natural water contents, grains size, Atterberg consistency limits, densities and specific weights of the clays in accordance with TSE The soil type has been identified as a result of the grain size analyses and consistency limit tests and the Unified Soil Classification System (USCS) (ASTM D standard) has been utilized concurrently. Furthermore, a revised plasticity chart developed from the original Casagrande and Polidori plasticity charts has been employed to identify the soil type as well. INDEX VALUES OF THE DOĞANHİSAR CLAYS As a result of the grain size analysis, it has been found that the grain sizes of the 5 samples are distributed within the following ranges; 32-59% silt, % sand, % clay and 5-21% gravel (Figure 2, Table 1). The liquid limit, plastic limit, shrinkage limit and plasticity index values representing the soil types were found to be in the range of %, %, and %, respectively (Table 1). Using the data obtained from the grain size analysis, the consistency limit tests and the Casagrande Plasticity chart employed in the Unified Soil Classification System (USCS) (ASTM D ), all of the clay samples taken 358

3 from Doğanhisar clay pit have been classified as low plasticity or medium inorganic clay (CL) (Figure 3). It has also been determined that the same soil type of the same set of samples should be specified as inorganic silt and very thin sand (ML) according to plasticity chart proposed by Polidori (2003) (Figure 4). As a result of the grain size analysis, the excessive silt concentration in the soil (32-59%) supports its specification as ML type soil assigned from the Polidori s plasticity chart (Figure 2, Table 1). According to the liquid limit classification by Sowers (1979), sample 2 has been found to belong to the slight compressible plastic soil category and rest of the samples into the medium compressible plastic soil group. In the light of the plasticity index values, samples no. 1, 3 and 4 have been identified as medium plastic and to have medium dry strength, sample no.2 as slightly plastic and slight dry strength, and finally sample no.5 as highly plastic and high dry strength (Sowers, 1979). The liquidity index (I L ) was found to be I L <0 and the consistency index (I c ) was found to be I c > 1 and therefore, they fall into the category of semi-plastic solid or solid soils. On the other hand, the samples have been evaluated by using the clay content-plasticity index chart proposed by Van Der Merwe (1964) and it has been ascertained that samples no.1, 2, 3 and 4 possess medium swell potential whereas sample 5 bears high. Table 1: Certain soil properties of the clay samples from Doğanhisar clay pit Number of samples Properties Water content (w -%) Liquid limit (LL-%) Plastic limit (PL-%) Rötre limit (w r -%) Natural unit weight ( -kn/m 3 ) Dry unit weight ( d -kn/m 3 ) Specific gravity (Gs) Degree of saturation (S-%) Void ratio (e -%) Porosity (n -%) Plasticitiy index (PI-%) Liquidity index (LI) -0, ,51-0,10-0,21 Consistency index (I c ) Activity (A) 1, Grain size Gravel -% 21, Sand- % 31, ,00 17,00 24,00 Silt -% 32, ,00 48,00 36,00 Clay- % 16, ,00 30,00 24,00 According to Casagrande Plasticity Chart CL CL CL CL CL According to Polidori Plasticity Chart ML ML ML ML ML 359

4 The activity (A) values of the samples have been determined in accordance with Skempton (1953). As a result, samples no.1 and 5 have been categorized as active clays (A>1.25), samples no. 2 and 3 as normally active (0.75<A<1.25) and sample no.4 as inactive clay (A<0.75). In a study conducted by Aksoy et al., in 2008, it was determined that the clays in the region were mostly composed of illite, kaolinite and chlorite type of clay minerals. It is known that there is a medium/high level of correlation between the type of clay mineral and its activity value. according to the activity values, the classification performed in this study exhibit partial conformity with results obtained in the study conducted by Aksoy et al. (2008). Figure 2: Particle-size distribution curve for Doğanhisar clay samples 360

5 Figure 3: Exhibition of Doğanhisar clay samples on Casagrande plasticity chart (ASTM D ) Figure 4: Exhibition of Doğanhisar clay samples on Polidori plasticity chart (Polidori, 2003) CONCLUSIONS As a result of the obtained data and conducted evaluations, it has been determined that the geological units at the investigated region generally consist of silt, sand and clay particles. The soils from investigated area were classified into the group of CL type of soils based on Casagrande plasticity chart which is employed in the Unified Soil Classification System (USCS) and into ML type soil group based on Polidori plasticity chart. The geological unit has been deemed to belong into semi-solid (very hard) soil group according to its liquidity and consistency indices. Finally, the analyzed soil samples were found to possess medium swell potential in consideration of the classification as per the unit s clay content and plasticity index. REFERENCES Aksoy R., İnce İ., Bozdağ A. and Hüseyinca M.Y., 2008, Geology and Mineralogy of The Doğanhisar Clay Beds (Central Anatolia, Turkey); International Scientific Conference SGEM 2008 Conference Proceeding Vol.: 1, p. ASTM D , 2003, Standart Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System), In: Annual Book of ASTM Standards. Volume 04.08, West Conshohocken, PA., pp Holtz,R.D. and Kovacs,W.D., 2002, Geoteknik Mühendisliğine Giriş, (Çeviren: Kayabalı, K.), Gazi Kitabevi, Ankara, 723s. (in Turkish) İnce, İ., 2004, Doğanhisar killerinin jeoteknik özellikleri, Selçuk Üniversitesi Fen Bilimleri Enstitüsü Jeoloji Mühendisliği Anabilim Dalı Yüksek Lisans Tezi(yayımlanmamış), Konya,89 s. (in Turkish) 361

6 Polidori,E., 2003, Proposal for a new plasticity chart, Geotechnique, Volume 53, No:4, pp Skempton, A.W.,1953, The Colloidal Aktivity of Clays, Proceedings of The Third İnternational Conference on Soil Mechanics and Foundation Engineering, Vol.I, pp Sowers, G. F., 1979, Introductory soil Mechanics and foundations: geotechnical engineering, 4th edition, copyright, Macmilan Publising Co., Inc., New-York, TS 1900, 1975, İnşaat Mühendislerinde Zemin Deneyleri, Türk Standartları Enstitüsü birinci baskı, Saim Toraman Matbaası, Ankara, s.172. (in Turkish) Umut, M., Karabıyıkoğlu, M., Saraç, G.,Bulut, V., Demirci, A.R., Erkan, M., Kurt, Z., Metin, S. ve Özgönül E.,1987, Tuzlukçu-Ilgın-Doğanhisar-Doğanbey (Konya ili) ve dolayının jeolojisi, MTA Enst., Arşivi, Rapor No:293, Ankara, s.51. (in Turkish) Van Der Merwe, D.H., 1964, The Prediction of Heave from The Plasticity Index and Percentage Clay Fraction, Trans SAICE, Vol.6, No.5, pp

4. Soil Consistency (Plasticity) (Das, chapter 4)

4. Soil Consistency (Plasticity) (Das, chapter 4) 1 What is Consistency? Consistency is a term used to describe the degree of firmness of fine-grained soils (silt and clay). The consistency of fine grained