Effectiveness of Spider Web Foundation Versus Raft Foundation in Resisting Static and Dynamic Loads at Liquefaction Prone Area

Abstract

As one of the earthquake-prone countries with liquefaction risk in certain soil conditions, Indonesia has developed innovative earthquake-resistant infrastructure. One of the innovations is Konstruksi Sarang Laba-Laba foundation (KSLL), literally translated as spider web foundation. The KSLL foundation system was invented by Ir. Sutjipto and Ir. Riyantori in 1976. This research compares the KSLL foundation against the conventional raft foundation in resisting static and dynamic loads. The study was based on data from University Hospital in Jember which uses KSLL as its foundation. Based on the soil investigation data, a water-saturated loose sandy soil, which is suspected to have liquefaction potential, was identified at a depth of 5-9 m. Based on liquefaction potential assessment, the study site has a high liquefaction potential with an LPI value of 27.7. Finite Element Method was used to compare the KSLL foundation against a raft foundation with equal concrete volume to the KSLL foundation. The results indicate that the KSLL foundation performs better than the equivalent raft foundation, having lower settlement under both static and dynamic loading conditions. Although higher axial forces were observed in the KSLL foundation, its overall performance remained superior. In contrast, the equivalent raft foundation developed high bending moments and shear forces, experiencing localized punching deformation. These findings demonstrate that the KSLL foundation provides a more effective foundation for structures constructed on liquefaction-prone ground by enhancing stability and reducing deformation.