Analisis Potensi Likuifaksi Menggunakan Metode Seed Et Al. (1985), Cetin Et Al. 2004) Dan Hyperbolic Fuction (2012) Berdasarkan Data N-Spt Akibat Pengaruh Variasi Magnitudo Gempa Analysis Of Liquifaction Potential Using Seed Et Al. (1985), Cetin Et Al. (2004) And Hyperbolic Fuction (2012) Methods Based On N-Spt Data Due To The Effect Of Earthquake Magnitude Variations (Studi Kasus Proyek Jembatan Kretek Ii Di Bantul, Daerah Istimewa Yogyakarta)

Abstract

Bantul Regency is part of the Special Region of Yogyakarta which is located in the south and borders the Indian Ocean. Lowlands in the middle of south coast often pose a threat of disasters with varying levels, one of which is earthquake. Liquefaction frequently occurs during earthquake when soil behavior happens due to the earthquake load in short time. Earthquake vibrations which propagate in the ground rapidly resulted in the soil mass transition from solid to liquid particles. This study is located in the Kretek II Bridge construction project, Bantul Regency, Yogyakarta Special Region. The formulation of the problem raised in this study is to analyse the value of the Safety Factor (SF) using 3 different methods, namely the Seed et al. (1985), Cetin et al. (2004), and HBF (2012) with variations in earthquake magnitudes of 6.3, 7.0 and 7.5 on the Richter Scale. Then how is the influence of the Safety Factor (SF) on variations in the magnitude of the earthquake, and how is the potential liquefaction that occurs at the points BM-K1, BM-K2, and BM-K3 The benefits of the research are to provide information on the potential for liquefaction that occurs at the Kretek II Bridge, provide information on the safe value of the liquefaction potential, and can be used as consideration for planning in Bantul Regency. The stages of this research are divided into 3, the first is the collection of field data and laboratory test data from the Soil Mechanics Lab, Islamic University of Indonesia. Then proceed with the analysis of the liquefaction potential with the output of the results of the liquefaction potential in the form of a graphic. Then the last step is writing a report and making conclusions. The results of the liquefaction potential analysis using the Seed et al. (1985) method, the Safety Factor (SF) value at the BM-K1 point varies from 0.707 to 1.442, at the BM-K2 point the variation in the SF value ranges from 0.691 to 1.427, and at BM-K3 the SF value ranges from 0.628 to 1.176. From the results of the analysis of the liquefaction potential using the Cetin et al. (2004) method, the Safety Factor (SF) value at the BM-K1 point varies from 0.090 to 2.344, at the BM-K2 point, the SF value varies from 0.113 to 2.261, and at BM-K3 the SF value ranges from 0.128 to 1.317, 3. From the results of the liquefaction potential analysis using the HBF (2012) method, the Safety Factor (SF) value at the BM-K1 point varies from 0.201 to 4.949, at the BM-K2 point the SF value varies from 0.208 to 0.990, and at BM-K3 the SF value ranged from 0.153 to 1.136. From the results of the analysis of the liquefaction potential using the 3 methods above, it can be concluded that variations in earthquake magnitude affect the SF value. The larger the magnitude of the earthquake, the smaller the SF value. The liquefaction potential occurs almost at all points at a depth of 4 m to 18 m.