EVALUATION OF THE SURFACE SETTLEMENT ABOVE THE PRAGUE METRO LINE A EXTENSION CONSTRUCTED BY TWO SHIELDS

Abstract

The new section of the Prague metro V.A is located in the west part of Prague, between stations Dejvická and Motol Hospital. The new metro section is 6.2km long and has four new stations. Majority of the two running tunnels that are 6.2km long were excavated by two EPB (Earth Pressure Balance) shields (2 × 4.8 km), it was the first use of modern tunnelling machines in the Czech Republic. Surface settlement above the running tunnels caused by the EPB shields was regularly monitored. The following paper is focused on an evaluation of the mentioned surface settlement using a volume loss. Consequently, numerical modelling of various cross-sections was executed. Modelling was realised by a finite element method in 2D, using the software Plaxis. Two different approaches were applied for modelling of the 3D effect in 2D. Important parameters Mstage and Cref were derived for the selected cross-sections by back analyses (comparison of the numerical modelling results with the results of monitoring). The results of realised numerical modelling and the volume loss evaluation can be used for a preparation and realisation of similar tunnels in similar geology (for example, construction of the Prague metro line D, which will probably also be excavated by the EPB shields).