M5 Metro Line Tunnelling Works and their Effect on the Hydraulic Structures of the Dambovita River

摘要

In order to carry out the M5 Metro line in Bucharest,the undercrossing of the hydraulic works related to the Dambovita River was required.The common technology for the metro tunnels is the earth pressure balanced excavation(EPB-TBM),precasted segment lining and back-fill grouting to minimize the surface settlements.The Dambovita River hydraulic development is made of 2 main components-the upper clean water channel and the sewage/drainage system cassette,placed below(the base slab of the channel representing the roof of the cassette).To evaluate the structural effects of the undercrossing on the existing hydraulic structures,a 3D finite element model was created,to simulate the sequence of construction works.The model was calibrated based on the measured settlements,during the execution works of the metro tunnels before reaching the undercrossing section(a region with similar geotechnical properties).The calibrated parameters were the elastic modulus of the backfill grout at early hardening stages and the length of the grout,still being in”gel phase”(with no stiffness).The paper presents a brief description of the existing and the designed structures,as well as the steps followed to create and calibrate the mathematical model.Concerning the results,the undercrossing area of influence is revealed,by longitudinal and transversal effects expressed in induced displacements and stresses.Several considerations and recommendations regarding the tunnelling works are made in order to avoid any damages to the existing facilities.