Digital engineering in identifying potentially settlement affected structures from adjacent tunneling and excavation

Potential settlement of structures from tunnelling and excavations have typically been manually identified through comparison of structures’ footprints against settlement modelling. This time-consuming exercise requires manual re-processing after every alteration in the settlement model and is prone to human error. As a part of large scale tunnel and excavation works, Golder Associates and PSM developed a digital engineering solution to automatically identify structures that are predicted to be affected by settlement, and its magnitude. The tunnels stretch for fifteen and a half kilometres through inner Sydney with six box cut excavations, the settlement model of which can now be re-analysed in less than half an hour.

Vertical displacement from initial state settlement was modelled, and Surfer used to output contours of the modelled settlement. These contours were intersected with the footprint of the structures along the route and the value of the greatest intersecting contour attached to the footprint. As a part of the settlement analysis, adjacent basements were also classified into proximity zones using horizontal and vertical distance of basements to box cut excavations and the tunnel walls. The 3D CAD models of the box cut excavations and the centreline of the tunnel were brought in and the angle and distances to the basements along the alignment calculated.

The scripts were created with the Extract, Transform and Load software FME, and the python package ArcPy. This solution is highly flexible and able to be adapted to other settlement effect analyses.