SOFT GROUND TUNNELLING | TECHNICAL


Above: Auger boring execution


The pipes were installed in 12m-long welded


segments from the portals and 6m-long segments from the shaft, using auger boring technology (Figure 5). In this method the pipes are jacked into the ground using hydraulic jacks, while soil is simultaneously being removed using an auger as a rotating cutting tool. The pipes were installed from the two portals and from each side of an intermediate shaft. Figure 6 shows photos during the installation from the portals. Initially, the contract required use of a closed face


TBM for pre-support construction but the TTP team convinced the client’s team that use of the suggested


auger boring method would provide better control of the settlements during pipe installation. Using this arrangement allowed the tunnelling team to manage settlement risks and ensure that the tunnel remained stable throughout excavation.


ADVANCED NUMERICAL MODELLING Due to the complexity of the project and the tight settlement tolerances, the team relied heavily on advanced numerical modelling to predict ground behaviour and assess the impacts of tunnelling on nearby structures.


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