Assessing the construction cost of Greek transportation tunnel projects

Abstract

Cost estimation is a crucial factor for the success of an engineering project. This element is even more important at the initial stages of design where decisions should be taken based on the more accurately available cost data. In underground construction projects especially, where the variability of the geotechnical conditions can change initial estimates, the accurate estimation of the construction cost from the preliminary phases of the project can minimize cost overrun issues as well construction claims and disputes. The purpose of this paper is to provide insight in cost estimation for underground projects focusing on tunnels. For this reason, the analysis of construction cost is undertaken, based on data from a set of 9 tunnels that have been constructed in Greece. The analysis presented focuses on the excavation and temporary support cost with respect to the geotechnical conditions encountered. Although the cost is influenced by many parameters, through the analysis of past data using the Case Base Reasoning approach, valuable lessons can be learned by decoding the effect of the ground conditions on the construction cost. The construction cost of the Greek tunnels is estimated for 2011 price levels and it is expressed though range estimation for 5 rock mass categories that were identified. Furthermore, a direct linkage between construction cost and the encountered geotechnical conditions, as expressed in GSI values, are made in an attempt to capture the general trend of construction cost in terms of €/m3 and €/m. The findings can be used as a first order assessment in order to have a representative estimation of the tunneling cost from the initial stages of project design.