GROUND CONDITIONING | TECHNICAL
Madrid M30 (2005) The next incredible step forward in soil conditioning was for the first giant EPB TBMs worldwide: 15m diameter machines. They were to work on the M30 motorway project, in Madrid. We all have been concerned that the necessary cutterhead torque on such machines could be extremely high since diameter influences torque to the cubic power! Therefore, we did extensive soil conditioning tests
in the laboratory and used a second generation of anti-clay foam, allowing to reduce the cutterhead torque significantly even with a completely filled and pressurised working chamber. See Figure 9 and Langmaack (2013). As a result of well applied and adopted soil conditioning, the average real cutterhead torque on the EPBMs on M30 remained half as important as expected and only at 30% of the installed torque. This jobsite is a perfect example of how well applied
soil conditioning – and we saw this on the Herrenknecht TBM as well as on the Mitsubishi TBM on the project – can protect the cutterhead well, reduce clogging and wear very efficiently, avoiding frequent chamber interventions as well as time consuming and more risky cutterhead tool change.
Special thanks to Claus Nielsen and Sören Nörtoft for their great support.
New Kaiser Wilhelm Tunnel (2011) A 10.54m-diameter dual mode HR/EPB TBM with constant screw conveyor muck-out was used for Deutsche Bahn’s (DB) New Kaiser Wilhelm rail tunnel project, in Germany. DB was doubling up capacity beside the existing, 1879-built, Kaiser Wilhelm railway tunnel. Starting with open hard rock excavation, the TBM was
supposed to reach the transition zone to the soft ground section with only 3.2m distance to building foundations. Therefore, in planning, DB insisted on the machine be switched to EPB mode, with a completely filled and pressurised working chamber, while still in the hard rock section and well before reaching the transition zone – something we had never done before.
As described in Langmaack (2016) and Langmaack
(2017), the solution finally applied was to undertake simultaneous injection of a strong foam and a polymer reinforced bentonite suspension at the cutterhead. This combination turned the hard rock chips and the fines created by the cutterhead into a compressible homogeneous paste (see Figure 10). The switch from hard rock open mode excavation
to fully pressurised EPB advance was tried a couple of times and then was successfully, finally, applied close to the predicted transition zone to soft ground. The conditioning system was also continued in the soft ground section with a subsequent reduction of the bentonite suspension injection as the amount of hard rock decreased.
Special thanks to Ulrich Rehm and Armin Strauss for all the challenges as well as for all the support.
Hamburg Elbe Crossing (2023) The Elbe crossing project for the Hamburg District Heating System passes through clay soil as well as gravelly sands of high permeability. From the lessons learned on earlier projects, the use of bentonite suspension along with polymers seems mandatory for the sandy section. To meet special concerns regarding the high water pressure and taking into account new ideas to increase tunnelling security and also to increase the efficiency of a fine filler injection, we at MC-Bauchemie have created the SolidFoam®
– which has undergone extensive testing at the RUB University, Bochum (Thewes 2023). Figure 11 shows the change of the soil permeability
coefficient k with different modes of conditioning, illustrating well the efficiency of applying a highly stable SolidFoam®
. More detailed research is in
progress and will be presented at the STUVA 2023 conference, in Munich, in November. The technology is to be first applied on the Elbe crossing EPB TBM in Hamburg.
Special thanks to Eugen Kleen and Markus Thewes for the initial ideas and belief in the concept.
Below left, figure 5: Aviles - inappropriate soil conditioning in Sand
Below right, figure 6: Aviles - well adopted soil conditioning in Sand
technology
November 2023
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