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| | Abstract | | A resistivity measurement system has been developed to discriminate soil types around a shield tunneling machine during the excavation. The electrode pad was installed at the sidepiece of the cutter blade (rotative part) so that the resistivity of the tunnel wall is continuously measured. A working prototype of the system was tested in a real tunnel construction project. It took about one year to excavate the tunnel of 2,800m long. As the result, the apparent resistivity map of the tunnel wall was clearly obtained. The threshold value of apparent resistivity for discriminating sand from silt was thought to be 27ohm-m, though the observed resistivity values contained the effect of existing excavation mud around the electrodes. We will continue to refine the system as a reliable method. |
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