Analisis Potensi Likuifaksi pada RS UII berdasarkan Data N-SPT

Abstract

Liquefaction is a phenomenon which soil loses its strength due to earthquake vibrations. This leads to the rise of water pore pressure and the fall of effective pressure in the soil. The liquefaction phenomenon tends to happen to fine and uniformly grained soil (sandy soil). As the Academic Hospital of Universitas Islam Indonesia is located at Jalan Srandakan No. KM, RW. 5, Jodog, Wijirejo, Pandak District, Bantul, Yogyakarta Special Region, in which Bantul Regency is one of the areas in the south of Java Island with a fairly high risk of earthquake. Therefore, it is necessary to conduct an analysis of the possibility of liquefaction in the hospital, one of which is an analysis that utilizes the N-SPT value. This research was held based on the earthquake strength in Yogyakarta on May 27, 2006 with the magnitude scale of 6,3 Mw. The liquefaction analysis utilizing the N-SPT data was conducted using the Youd-Idriss method (2001), Seed et al method (1976), and Valera-Donovan method (1977).The liquefaction analysis results in the UII Hospital using the Youd-Idriss method (2001) indicated that the point of SPT BM-01 has a liquefaction potential at the depth of 8 – 18 meters. As for BM-02, the liquefaction potential stood at a depth of 4 – 18 meters. The outcomes of the liquefaction analysis with the Seed et al method (1976) showed the points of BM-01 and BM-02 each have the risk of liquefaction because the NL value in each layer at its respective points were less than the value of Neq = 6,8 (NL < Neq). As for the liquefaction analysis based on the Valera-Donovan method (1977), the points of BM-01 and BM-02 in the 14 – 18 meter layers had the potential of the occurrence of liquefaction. This happens due to the smaller value of N-SPT (N) compared to the Ncrit value (N<Ncrit).