Analisis Balik Galian Dalam dengan Metode Konstruksi Top Down Menggunakan Analisis Elemen Hingga 2-Dimensi dan 3-Dimensi
DOI:
https://doi.org/10.5614/jts.2022.29.1.4Keywords:
Analisis balik, Defleksi dinding, Deformasi tanah, Galian dalam, Metode elemen hingga, Metode konstruksi top downAbstract
Abstrak
Kasus galian dalam perlu mendapat perhatian khusus terkait defleksi dinding dan deformasi tanah yang dipicu akibat galian dalam itu sendiri. Defleksi dinding maupun deformasi tanah yang berlebihan dapat menyebabkan kerusakan pada struktur sekitarnya. Untuk memverifikasi performa maupun keamanan pekerjaan galian dalam dapat dilakukan analisis balik. Penelitian ini berfokus pada analisis balik terhadap pekerjaan galian dalam pada salah satu bangunan perkantoran tersohor di Indonesia. Galian ini menggunakan metode konstruki top-down dengan dinding diafragma berdiameter 0,8m sebagai sistem penahan. Melalui penelitian ini, diketahui bagaimana jika parameter hasil analisis balik dengan metode elemen hingga 2-Dimensi digunakan dalam analisis 3-Dimensi. Analisis menggunakan model material Hardening Soil dan analisis balik mengacu kepada hasil pengukuran inklinometer. Berdasarkan hasil analisis diperoleh bahwa analisis 3-Dimensi memberikan hasil defleksi dinding dan deformasi tanah yang underestimated dibandingkan dengan analisis 2-Dimensi. Hal ini disebabkan oleh efek 3-Dimensi yang berperan signifikan. Jika dilakukan iterasi parameter agar diperoleh hasil defleksi dinding yang sesuai antara analisis 3-Dimensi dengan hasil pengukuran lapangan, nilai modulus tanah perlu direduksi hingga 80% pada kasus ini. Artinya, nilai modulus tanah menjadi parameter yang berperan penting dalam memprediksi besarnya defleksi dinding akibat galian. Selain itu, besarnya defleksi dinding dan deformasi tanah juga dipengaruhi oleh faktor kedalaman galian.
Kata-kata Kunci: Analisis balik, defleksi dinding, deformasi tanah, galian dalam, metode elemen hingga, metode konstruksi top-down
Abstract
Deep excavation needs special attention regarding wall deflection and soil deformation induced by the excavation work itself because excessive one can cause damage to the vicinity structure. Back analysis can be carried out to verify the performance and the safety of excavation. This research focuses on the back analysis of deep excavation in a famous office building construction in Indonesia. The excavation was executed using top-down construction method with diameter 0.8m of diaphragm wall as a retaining system. Through this research, it can be known how the parameter of back analysis using 2-Dimensional finite element method is modeled in 3-Dimensional analysis. Soils were modeled as a Hardening Soil model and back analysis was referred to inclinometer measurements. Based on the analysis results, it was found that 3-Dimensional analysis gave underestimated wall deflection compared to 2-Dimensional analysis. It is due to the 3D effect that performed significantly. If the soil parameter was iterated to obtain relevant wall deflection between 3-Dimensional analysis and field measurement, soil modulus needs to be reduced by 80% in this case. It means that soil modulus becomes an essential parameter in predicting wall deflection induced by excavation. Besides, excavation depth also affected wall deflection and soil deformation.
Keywords: Back analysis, deep excavation, finite element method, soil deformation, top-down construction method, wall deflection
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