ANALISIS PERHITUNGAN KAPASITAS DAYA DUKUNG SPUDCAN PADA JACK-UP RIG DENGAN METODA ELEMEN HINGGA
Vidya Paramita Nilammurni 1 dan Hendriyawan 2
Program Studi Teknik Kelautan
Fakultas Teknik Sipil dan Lingkungan, Institut Teknologi Bandung,
Jl Ganesha 10 Bandung 40132
1 vdy_paramita@yahoo.com dan 2 hendriyawan@ocean.itb.ac.id
Abstract: Jack-up drilling rigs are a type of mobile platform that is used extensively for exploration of offshore oil and gas fields. The main components of jack-up rig consist of hull, legs and footings, and the equipment or deck. Hull is a structure that supports the equipment, system, and personnel. Deck is where the equipment is placed. Legs and footings are acts as a medium to transmit the loads (jack-up rig loads) to the soil or rock below it. The accident which occured on the jack-up rig is largely due to the soil failure relating to the foot of jack-up rig. Therefore, this research is proposed to develop a method in calculating bearing capacity of spudcan jack-up rig foundation. By using the concept of shallow foundation calculation, there are two methods in calculating the ultimate bearing capacity of spudcan jack-up rig: using semi empirical formula based on code for jack-up rig design (SNAME 2002) and using finite element method (FEM). This research will be analyzed in homogeneous clay soil condition and in condition of multiple layers or actual condition (the location of data is at offshore east java or west Madura). This research assumed in non-backflow condition. The result of semi empiric calculation is in the form of graphs that represent ultimate bearing capacity to depth of penetration compared with the result of finite element calculation. The objextives of this study is to obtain a specific soil parameter of spudcan model (such as modulus young and poisson ratio) for finite element modeling. Thus, the soil and spudcan model can be used for more complex analysis such as earthquake analysis and the effect of jack-up rig installation to adjacent existing structure. Based on finite element modeling, the results for homogeneous clay soil are relatively close to semi-empirical calculation. The result of FEM for layered clay soil is slightly diferent compare to semi empirical. This is due to FEM used in the analysis has some limitation in modeling the condition of squeezing clay (weak clay soil layer over strong clay soil layer conditions) and punch-through of strong clay soil layer over weak clay soil layer.
Keywords: jack-up rig, spudcan, bearing capacity, SNAME, finite element method
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