RECENT DEVELOPMENTS IN SITE INVESTIGATION AND TESTING FOR HARD ROCK TBM PROJECTS
For several recent TBM tunnel projects, unexpected ground conditions have been encountered, causing extra cost, considerable delay, and in some cases major claims. Undoubtedly, insufficient and/or irrelevant site investigation and testing are among the main causes of such incidents. The purpose of this paper is to review the main investigations and tests relevant for hard rock TBM projects, with particular emphasis on the considerable development that has taken place over the last few years. Also, guidelines for defining optimum scope and extent of site investigations and testing are discussed, as well as the importance of adjusting the investigations and tests according to complexity of the ground conditions and project type.
Estimating cost for transportation tunnel projects: a systematic literature review
Estimating the cost of transportation tunnel projects during the feasibility stage is highly complex and challenging for state/federal agencies. The use of traditional methods to estimate tunnel project costs has led to significant cost underestimation because of limited information/data to compare different alternatives. To address cost underestimation, 40 cost estimating factors were identified by conducting a systematic literature review. Seven electronic databases were searched and articles were screened based on pre-established criteria. Of the 788 articles retrieved, 39 articles published from 1988 to 2013 met the inclusion criteria and were included in the review. The resulting data was analysed using descriptive and Anderson–Darling statistical methods. The results of the analysis showed that the top five factors contributing to cost underestimation were engineering and construction complexities, geological conditions, cost estimation, market conditions, and environmental requirements. The findings from the review showed the importance of incorporating the effect of each determined estimating factor by state/federal agencies or metropolitan planning organizations when preparing initial estimates to avoid cost underestimation and/or to reduce the errors associated with such estimates. Future research may be warranted to explore the possibility of weighting the factors.
Design of reinforced concrete lining in pressure tunnels, considering thermal effects and jointed rockmass
Abstract Jaeger's theory (Jaeger, Rock Mechanics and Rock Engineering , Cambridge University Press, 1972) of the design of the lining for a pressure tunnel applies to a tunnel located in an isotropic, homogeneous and elastic medium. The theory is derived from the elasticity equations for the plane stress condition. In this paper, Jaeger's theory is extended to a plane strain situation. Also included is a discussion of the effects of a uniform increase (or decrease) in the lining temperature, jointed rockmass, cracking of the tunnel lining, and cracking of the rockmass around the opening. Tables are presented for the modulus of subgrade reaction for various rockmass conditions and for rock sharing pressures for various lining conditions. The reduction factor to include the effect of joints in rockmass is derived by the analysis of a numerical model of the lined tunnel by the finite-infinite-interface element method.