Soil improvement by jet grout method against liquefaction: Example of Samsun-Tekkeköy

This study comprises of the liquefaction evaluation of a site that is located in Tekkeköy district of Samsun province which is approximately 57 km distant from North Anatolian Fault Zone (NAFZ) and the implementation of soil improvement by jet grout method with the aim of increasing resistance against possible risk of liquefaction. For this purpose, peak horizontal acceleration at ground surface values belonging to scenario earthquakes with the magnitudes of 6.0, 6.5, 7.0 and 7.2 were determined through the use of attenuation relation of earthquake which was developed for Turkey's earthquakes. Through the use of these acceleration values and the blow counts that were obtained through Standard Penetration Tests (SPT) which were performed in 12 boreholes, liquefaction risk analyses were carried out with "Simplified Procedure" that was developed by Seed and Idriss (1971). Additionally, settlements which may occur on soil strata due to liquefaction were calculated in accordance with the methods of Tokimatsu&Seed (1986) and Ishihara&Yoshimine (1992). According to these methods, it was designated that the highest settlement values were obtained within the scope of scenario earthquake with the magnitude of 7.2. On the inspection site that was determined as having liquefaction risk and possibility of excessive settlements, the method of jet grout that has been commanly used in Turkey and that is able to be applied almost any type of soil was chosen with the aim of eliminating the effects of liquefaction. Within this scope, optimal solution was obtained with 616 pieces of 8 m and 12 m jet grout columns with the diameter of 0.65 m, and liquefaction risk was eliminated as well as a threefold improvement was obtained the bearing capacity of the foundation soil. Key Words: Liquefaction, Liquefaction Risk Analysis, Soil Improvement, Jet Grout.