Parametric modelling based approach for efficient quantity takeoff of NATM-Tunnels

Purpose As every construction project is quite different according to the type of construction, 3D-representations on design, estimation, construction, and management also need to be different. While the 3D-approach has been widely applied to building projects, it has rarely been tested on large construction projects such as tunnels, mass transit systems, dams, highways, etc. Meanwhile, characteristics of NATM (New Austrian Tunnelling method) tunnel projects– including long-linear-simple shapes, cyclic-repetitive operations, and relatively small numbers of objects–are compatible with parametric modeling that can be supported by BIM-applications. The purpose of this paper is to propose an efficient approach for quantity takeoff of NATM-tunnels, using parametric modeling. Method NATM-tunnel characteristics are described that should be applied to the 3D-modeling and technical requirements for parametric modeling functions toward obtaining efficient solutions. Results & Discussion Results from a pilot project indicate that standardization on tunnel libraries, parameters, levels of detail, and parametric relationships can dramatically improve the efficiency of quantity takeoffs.