A Study on Tensile Strength of Compacted Fine-Grained Soils

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ORIGINAL PAPER

A Study on Tensile Strength of Compacted Fine-Grained Soils Volkan Dagar

. Erdal Cokca

Received: 26 November 2018 / Accepted: 17 August 2020 Ó Springer Nature Switzerland AG 2020

Abstract The tensile strength of clay is a major mechanical parameter and the main controlling parameter of tensile crack development which is generally encountered in geostructures. In this experimental study, 8-shaped direct tensile test and split tensile test were used to measure the tensile strength of compacted clay soil. Unconfined compression tests on the same clay samples were also carried out. Tensile strength and unconfined compression test results were compared. Laboratory tests were performed on Ankara clay and Kaolin clay with the addition of various proportions of synthetic polypropylene fiber, pulverized rubber, metal swarf, and bentonite. The data between the results of 8-shaped direct tensile tests, split tensile tests, and unconfined compression tests were correlated. This usage of different stabilizing agents enabled the authors to observe the reliability of the tensile strength measurement methods when soils’ mechanical properties were significantly changed and to develop universal equations which also can be applied to stabilized soils. The ratio of 8-shaped tensile strength to split tensile strength and to unconfined compressive strength was calculated to be 1.9 and 0.4, respectively. Also, the ratio of split tensile V. Dagar (&)  E. Cokca Department of Civil Engineering, Middle East Technical University, Ankara, Turkey e-mail: [email protected] E. Cokca e-mail: [email protected]

strength to unconfined compressive strength was calculated to be 0.2. Three equations were developed according to the Ankara clay and Kaolin clay mixtures’ tensile strengths, index properties, and compaction characteristics and proposed to estimate the tensile strength of fine-grained soils from their index properties. Keywords Tensile strength  Direct tensile test  Split tensile test  Unconfined compressive strength  Clay  Kaolin clay Abbreviations LL Liquid limit (%) PL Plastic limit (%) SL Shrinkage limit (%) PI Plasticity index (%) CC Clay content (%) List of Symbols Gs Specific gravity qdmax Maximum dry density (Mg/m3) w Water content (%) wopt Optimum water content (%) qu Unconfined compressive strength (kPa) Es Modulus of elasticity of soil (MPa) rt8 8-Shaped direct tensile strength (kPa) rtsplit Split tensile strength (kPa) Tmax Maximum tensile load (kN) P Compressive load on the cylinder (kN)

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Geotech Geol Eng

D L A

Diameter of the cylindrical specimen (m) Length of the cylindrical specimen (m) Cross-sectional area (m2)

1 Introduction The tensile strength of soil has generally been considered to be zero or insignificant compared to the soils’ compressive or shear strength. The general idea that the soils’ tensile strength is insignificant originates from the relatively low value of the tensile strength of the soil and limited geotechnical laboratory

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