Evaluation of the Impacts on Existing Elevated Structure of the Expressway due to Sinking Shafts in Bangkok MWA Project

The construction of reinforced concrete shafts for launching and receiving the TBM of Metropolitan Waterworks Authority tunnels under contract number G-TN-9D involves the sinking process of two circular shafts, each 36.7 m deep, with an inner diameter of 12 and 10 m for shaft 9D-3 and shaft 9D-4, respectively. These shafts are situated in close proximity, approximately 12 m apart from the existing elevated structure of the Kanchanaphisek Expressway (Bang Phli-Suksawat). Consequently, the ground movements induced by the sinking process of both shafts can potentially damage the existing structure. Hence, as the existing
structure is currently in operation, analyses of the impacts are essentially considered without compromising its functionality and serviceability. This paper presents the numerical simulation using the PLAXIS 3D software package, and the analysis results are discussed corresponding to the acceptable limits of the
structure. Additionally, the establishment of the AAA level for the instrumentation program is described as a proactive measure
to prevent risks or damage during the construction of both shafts
in the project.