Studi Kehandalan Metode Analisis Likuifaksi Menggunakan SPT Akibat Gempa 8,6 Mw, 12 September 2007 di Area Pesisir Kota Bengkulu
DOI:
https://doi.org/10.5614/jts.2018.25.1.7Keywords:
Likuifaksi, gempa, faktor keamanan, probabilitasAbstract
Abstrak
Naskah ini menyajikan hasil studi potensi likuifaksi di kawasan pesisir Kota Bengkulu, berdasarkan gempa berkekuatan 8,4 Mw, yang terjadi pada 12 September 2007 silam. Penelitian ini dilakukan dengan menganalisis potensi likuifaksi berdasarkan data SPT menggunakan metode empiris yang paling sesuai dari beberapa metode empiris yang lazim digunakan. Untuk memperoleh metode analisis yang paling sesuai, dilakukanlah perbandingan hasil analisis dengan data kejadian likuifaksi di lapangan. Metode yang paling sesuai adalah metode yang memiliki nilai faktor bobot kesalahan terendah. Metode tersebut selanjutnya digunakan untuk menentukan faktor keamanan likuifaksi nilai probabilitas likuifaksi (PL). Hasil penelitian ini memperlihatkan bahwa Metode Idriss-Boulanger merupakan metode yang paling mendekati dalam mengestimasi kesesuaian prediksi dan kejadian di lapangan. Berdasarkan hasil analisis menggunakan metode tersebut, likufaksi sangat berpotensi terjadi pada area yang diteliti. Kondisi kritis likuifaksi (faktor aman sama dengan 1) dapat terjadi dengan nilai probabilitas sebesar 0,495 khususnya pada tanah pasir sedang sampai dengan padat.
Abstract
This paper presents a study of liquefaction potential in coastal area of Bengkulu City caused during the 8.4 Mw earthquake event on 12 September 2007. To determine the most suitable method, all methods are compared with the liquefaction event data, by fitting concept. The most suitable method was selected as the smallest error weighted factor. The suitable method is then used to determine factor of safety (FS) against liquefaction and probability of liquefaction (PL). The result shows that the suitable method in estimating the suitability of prediction and field data is Idriss-Boulanger method. In general, Liquefaction could occur at the investigated area. The critical condition of liquefaction could happen with PL of 0.495, especially medium-dense sands.
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