Effects of curved shield tunnelling adjacent to existing power tunnel

Abstract

With the continuous development and utilisation of urban underground space, new urban tunnels will inevitably affect the formation of nearby existing structures. Methods to minimise the environmental impact induced by tunnel construction have been a hot topic of research in recent years. Based on the approach of Shanghai’s 9th line to the existing 110 kV electric cable tunnel, many different cases involving two adjacent tunnels have been simulated to measure the influence induced by shield-driven curve tunnelling passing through an area with adverse geological conditions. To make up for the disadvantages of the traditional manual monitoring, an automatic monitoring feedback network was constructed to ensure the operational safety of existing tunnels and validate the applicability of numerical models. Both the numerical prediction and field test data showed that reasonable construction parameters for the shield, real-time monitoring feedback, and timely grouting are effective means to guarantee smooth construction. Both the empirical correlations and analysis demonstrated that the distance should be more than twice the diameter of the new tunnel to guarantee that the settlement of the existing tunnel is no more than 10 mm. The simulation predictions for surface settlement also matched the field measurements very well, except for the case where a low grouting volume of 2.2 m3 was obtained.