Analisis Potensi Likuefaksi pada Bangunan Underpass Bandara YIA berdasarkan Simulasi Numeris

NOCHYZA HUSNUL K, Dr. Ir. Ahmad Rifa'i, M.T. ; Dr. Eng Sito Ismanti, S.T., M.Eng.

2021 | Tesis | MAGISTER TEKNIK SIPIL

Pembangunan Underpass Bandara Yogyakarta International Airport (YIA) terletak di Pesisir Pantai Selatan Jawa dengan zona subduksi lempeng dikenal dengan The Jawa Meganthrust yang menyebabkan potensi gempa cukup besar dan rentan terhadap likuefaksi. Likuefaksi adalah perubahan masa tanah dari padat menjadi cair akibat beban gempa (getaran) yang menyebabkan kerusakan permukaan tanah dan penurunan tanah yang berdampak pada infrastruktur. Tujuan dari penelitian ini adalah untuk mengetahui nilai faktor aman (SF) secara analitis dan numeris serta kestabilan pada struktur underpass. Penelitian ini dilakukan dengan menggunakan tiga titik bor, yaitu BH-06' dan BH-11' berada di tepi underpass, dan BH-10' berada di tengah underpass. Analisis potensi likuefaksi dilakukan secara analitis menggunakan metode Seed (1984) dan numeris dengan perangkat lunak Settle 3D sebagai pembanding hasil. Selain itu, analisis kestabilan struktur underpass dilakukan dengan simulasi numeris Plaxis v8.6. Hasil analisis potensi likuefaksi dengan metode Seed (1984) dan software Settle 3D memiliki SF relatif sama berkisar 0,208-1,483 yang berarti likuefaksi terjadi pada sisi tepi underpass titik bor BH-06' dan BH-11' di kedalaman 4-6 m dari muka air tanah 3,6 m dan 3,1 m. Sedangkan pada tengah underpass titik bor BH-10' dari muka air tanah 6,13 m aman terhadap potensi likuefaksi. Hasil simulasi numeris plaxis v8.6 pada titik bor BH-06', BH-10', dan BH-11' struktur fondasi underpass Bandara YIA memenuhi syarat keamanan terhadap penurunan.

The underpass construction of the Yogyakarta International Airport (YIA) is located on the South Coast of Java with a plate subduction zone known as the Java Meganthrust which causes a massive earthquake potential and is prone to liquefaction. Liquefaction is the change in soil mass from solid to liquid due to earthquake loads (vibrations) which cause damage to the soil surface and land subsidence which impacts infrastructure. The purpose of this research was to determine the value of the safety factor (SF) analytically and numerically as well as the stability of the underpass structure. This research was conducted by using three drill points, namely BH-06 'and BH-11' at the edge of the underpass, and BH-10 'in the middle of the underpass. Liquefaction potential analysis was carried out analytically using the Seed (1984) method and numerically with the Settle 3D software as a comparison of results. In addition, the underpass structural stability analysis was carried out by using numerical simulation of Plaxis v8.6. The results of liquefaction potential analysis using the Seed method (1984) and Settle 3D software have relatively the same SF range from 0,208 -1,483, which means that liquefaction occurs on the edge of the underpass with drill points of BH-06 'and BH-11' at a depth of 4-6 m, 3,6 m and 3,1 m from groundwater level. Meanwhile, in the middle of the underpass with drill point of the BH-10' from the groundwater level is 6,13 m safe against the potential for liquefaction. The result of a numerous simulation Plaxis v8.6 at the drill points of BH-06', BH-10', and BH-11', the foundation stucture of the YIA underpass fullfills the safety requirement against displacement.

Kata Kunci : underpass, likuefaksi, Settle 3D, Plaxis v8.6