4D approach for urban tunnelling in a BIM environment

In underground works, one topic that must be carefully studied and analysed is how to deal with interferences induced on buildings by the excavation machine. The paper provides a proposal for the management of the behaviour that must take place in the event of a building falling in a subsidence basin by creating a 4D BIM model able to control the influencing parameters, to visualise subsidence values and to foresee harmful events. To predict the formation of chimneys that could damage buildings structures and facades, the method assumes some predefined design values of the expected subsidence graphically monitoring, over time, different thresholds that can promptly activate safety procedures. The proposed model makes possible, as well, to check the tunnel ring parameters linked to the TBM machine. Dynamo has been used to semi-automatically connect an Excel file with a Revit one to import all the data in the 3D model. As a case study, the paper shows the application of the method to a portion of the central section of the new M4 metro line in Milan, where EPB-type TBM machines have been used. An additional output of the research consists of seven safety guidelines for interference management to be adopted when operational values exceed the assigned threshold. According to all the technicians involved in the M4 metro line site as specialists, the joint use of the 4D BIM model and the set of the safety procedures improve tunnelling management and can be applied with the appropriate changes in similar works.