Non-Linear Site Response Analysis For Evaluating Liquefaction Hazard Maps

ANISA NUR AMALINA, Prof. Ir. T. Faisal Fathani, S.T., M.T., Ph.D., IPU., ASEAN.Eng.

2021 | Tesis | MAGISTER TEKNIK SIPIL

Gempa dengan mekanisme strike-slip terjadi pada tanggal 26 Mei 2006 di Yogyakarta. Survei Geologi AS (USGS) memperkirakan momen gempa berkekuatan 6,3. Peneliti menyimpulkan bahwa kerusakan disebabkan oleh faktor amplifikasi dari sedimen lunak yang diendapkan dari Gunung Merapi. Kerusakan yang terjadi diperkirakan disebabkan oleh likuifaksi karena ditemukannya gejala likuifaksi seperti sand boils dan lateral spreading. Penelitian ini melakukan analisis respon tanah non-linier dengan disipasi tekanan air pori untuk menghasilkan respon dinamik tanah yang lebih spesifik dan akurat akibat gempa. DEEPSOIL digunakan untuk melakukan analisis respon tanah satu dimensi dan non-linier dengan disipasi tekanan air pori. Riwayat waktu akselerasi dipilih dari database NGA-west2 dengan mempertimbangkan parameter de-agregasi, MD= 6,5 dan RD= 14,5 km. Selanjutnya, hasil penelitian ini adalah Peta Percepatan Permukaan Maksimum, Peta Indeks Potensi Likuifaksi, dan Peta Indeks Keparahan Likuifaksi. Hasil penelitian menunjukkan bahwa endapan tanah di daerah penelitian bervariasi antara 40 m sampai 90 m. Perhitungan berdasarkan SPT menunjukkan bahwa semua data tergolong tanah sedang kecuali Makam Imogiri. Sejarah waktu dari Gunung Hamilton, Danau Coyote, dan CA Parkfield-02 dipilih dan diskalakan dengan faktor 18 hingga 33. Analisis DEEPSOIL menemukan bahwa amplifikasi terjadi di dua lokasi di Bantul, yaitu Pundong (BH-13) dan Nangsri ( BH-22). Lokasi yang mengalami amplifikasi tinggi termasuk dalam zona kerusakan tinggi hingga sangat tinggi.

An earthquake with a strike-slip mechanism occurred on May 26, 2006, in Yogyakarta. The US Geological Survey (USGS) estimated the earthquake moment magnitude as 6.3. Researchers inferred that the damage was controlled by amplification factors from soft sediments redeposited from the active Mount Merapi. The damages founded were predicted caused by liquefaction since the appearance of liquefaction symptoms were found, namely sand boils and lateral spreading. This study conducts a non-linear ground response analysis with pore water pressure dissipation to generate more specific and accurate soil dynamic responses due to earthquakes. DEEPSOIL was used to perform one-dimensional and non-linear ground response analyses with pore water pressure dissipation. The acceleration time history was selected from the NGA-west2 database by considering the de-aggregation parameters, MD= 6.5 and the RD= 14.5 km. Furthermore, this study results were Maximum Surface Acceleration Map, Liquefaction Potential Index Map, and Liquefaction Severity Index Map. The result shows that the soil deposits of the study area vary between 40 m to 90 m. The SPT-based calculation shows that all data are classified as medium soils except for Makam Imogiri. The time history from Mount Hamilton, Coyote Lake, and Parkfield-02 CA was selected and scaled by a factor of 18 to 33. The DEEPSOIL analyses found that amplification occurred in two locations in Bantul, namely Pundong (BH-13) and Nangsri (BH-22). Locations that experience high amplification were included in the high to very high damage zone.

Kata Kunci : DEEPSOIL, local site effect, young volcanic sediment, amplification, LPI, LSI