Non-linear Analysis of Pile Foundation in Liquefiable Soil Using Dynamic Constitutive Model and Seismic Hazard Analysis

Yoga Setiawan, Prof. Ir. Teuku Faisal Fathani, S.T., M.T., Ph.D., IPU, ASEAN.Eng.; Dr.Eng. Fikri Faris, S.T., M.Eng.

2024 | Tesis | S2 Teknik Sipil

Dampak likuifaksi akibat gempa bumi pada pondasi tiang pancang masih sangat parah, merusak dan memakan biaya yang besar. Dalam penelitian geoteknik, analisis fenomena likuifaksi masih menjadi topik penelitian yang dikembangkan khususnya pada model konstitutif dinamik tanah. Model konstitutif dinamik tanah yang dikembangkan untuk analisis likuifaksi adalah PM4Sand. Namun model konstitutif ini masih perlu dikaji ulang mengenai kesesuaiannya untuk konstruksi geoteknik seperti pondasi tiang pancang. Pada penelitian ini analisis pondasi tiang pancang non-linear terhadap pengaruh likuifaksi dibagi menjadi dua analisis yaitu analisis seismik menggunakan bahaya seismik probabilistik dan analisis likuifaksi menggunakan metode penilaian likuifaksi dan elemen hingga. Program ZMAP7, ArcMap dan R-CRISIS digunakan untuk analisis seismik. Program RS2 dengan model konstitutif PM4Sand digunakan untuk analisis likuifaksi non-linier. Hasil penelitian berupa peta percepatan tanah, penilaian likuifaksi, dan perilaku pondasi tiang pancang pada tanah likuifaksi. Berdasarkan Peta Percepatan Tanah, nilai sebaran bahaya di PGA di Provinsi Maluku mencapai 0,02g hingga 0,48g untuk kala ulang 500 tahun dan 0,04g hingga 0,79g untuk kala ulang 2.500 tahun. Tingkat kerentanan tertinggi terdapat di wilayah utara meliputi Pulau Seram, Pulau Way Apu, dan Pulau Ambon dan tingkat kerentanan terendah terdapat di wilayah timur termasuk Pulau Aru. Kedalaman tanah likuifaksi di daerah penelitian mencapai kedalaman 20 m dengan potensi likuifaksi sangat tinggi dan indeks keparahan likuifaksi tinggi hingga sangat tinggi. Desain pondasi tiang pancang yang dipilih berdasarkan pemodelan RS2 adalah pondasi tiang pancang dengan diameter 0,4 m dan kedalaman 24 m.

The effect of earthquake-induced soil liquefaction on pile foundations was still severe, damaging and costly. In geotechnical research, liquefaction phenomena analysis was still a research topic developed especially on soil dynamic constitutive models. The soil dynamic constitutive model that was being developed for liquefaction analysis was PM4Sand. However, this constitutive model still needed to be reviewed regarding its suitability for geotechnical construction such as pile foundations. In this research, the non-linear pile foundation analysis on the liquefaction effect was divided into two analyses such as seismic analysis using probabilistic seismic hazard and liquefaction analysis using liquefaction assessment and finite element method. ZMAP7, ArcMap and R-CRISIS programs were used for seismic analysis. The RS2 program with the PM4Sand constitutive model was used for non-linear liquefaction analysis. The results of this research were ground acceleration maps, liquefaction assessment, and pile foundation behaviour in liquefiable soil. Based on Ground Acceleration Maps, the hazard distribution value at PGA in Maluku Province reached 0.02g to 0.48g for a return period of 500 years and 0.04g to 0.79g for a return period of 2,500 years. The highest level of vulnerability was in the northern region including Seram Island, Way Apu Island and Ambon Island and the lowest level of vulnerability was in the eastern region including Aru Island. The depth of liquefiable soil in the study area reached a depth of 20 m with a very high liquefaction potential and high to very high liquefaction severity index. The pile foundation design chosen based on RS2 modelling was a pile foundation with a diameter of 0.4 m and a depth of 24 m.

Kata Kunci : liquefaction, dynamic constitutive model, finite element analysis, probabilistic seismic hazard analysis, pile foundation