Volume loss in shallow tunnelling

Although volume loss has an important effect in estimating the ground movements due to tunnelling in the design stage, this parameter is often determined by experience. This makes it difficult to estimate the impact on volume loss when changing project parameters like soil conditions, depth of the tunnel or sensitivity of the surroundings. This paper investigates the relationship between volume loss and cover-to diameter C/D ratio in shallow tunnelling. Based on a number of (empirical) relations from literature, such as the stability number method and an analysis of the bentonite and grout flows, volume loss at the face, along the shield and at the tail is determined. Long-term volume loss behind the shield is also estimated by means of consolidation. In this way a band width of achievable volume loss for future projects is derived. (C) 2016 Elsevier Ltd. All rights reserved.