Evaluation of measured movements due to NATM tunnelling in Copenhagen by means of plane models in FLAC

摘要

The new Metro in Copenhagen comprises approx. 8.5km of twin bored tunnels of which 500m are constructed by means of NATM (New Austrian Tunnelling Method). The tunnels are mainly constructed in the Copenhagen Limestone - a hard soft or soft rock. Experience shows that the limestone is well-suited for NATM construction. The maximum surface settlements above the largest caverns are 5-10mm with the movements of the tunnel crown in the same order. These observations are not in accordance with the predictions based on the rock mechanical classification, which indicates that the limestone is of a very poor quality, unsuited for mining. A back-analysis is carried out for the largest NATM cavern, Sjaeleboderne crossover, in order to calibrate a model basedon the convergence-confinement method for 2D analysis of tunnelling.