Design and construction of Cisumdawu tunnel, West Java, using umbrella grouting protection

Abstract

Construction of tunnel in soils used to be by using Tunnel Boring Machine (TBM), or otherwise by cut and cover method. Geological condition at Cisumdawu Tunnel in West Java is soft to medium soils in the upper layer and subsequently underlain by stiff to hard clay, where the tunnel is located. Tunnel diameter is 14 m including the structural concrete protection cover. Method of construction is by using umbrella grouting protection surrounding the tunnel opening. To obtain data for geotechnical analysis, the site was characterized by drilling with SPT and Pressuremeter Test (PMT). The particular objective of PMT is to obtain the at rest pressure, the soil moduli, the yield pressure and limit pressure, which is essential information for the design. Three dimensional (3D) finite element analysis was conducted to verify the design following the sequence of the method of construction known as the New Austrian Tunneling Method (NATM). The results show consistent movement by measurement during construction. Lesson learned from this exercise is that in-situ testing for site characterization by PMT and the input on initial stress are beneficial. Preliminary calculation gives sufficient insight into the anticipated problems, although in reality, the soil parameters must be adjusted.