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| | Abstract | | The number of tunnel projects in urban areas has recently increased. In such projects, it is important to detect weak sand layers lying between soft rocks such as mudstones, and improve its strength and permeability by grouting to minimize the risks of tunnel collapses, water inflow into tunnels and ground settlement etc. The authors expect that 3D resistivity tomography is a useful geophysical investigation, and conducted a series of laboratory experiments to verify the detection of thin sand layer lying between mudstones by 3D resistivity tomography. Furthermore, the sand layers were grouted by chemical grout and cement grout, 3D resistivity tomography was carried out again to evaluate the grouting effect. As a result, first, the sand layers were detected as high resistivity area by 3D resistivity tomography. Secondly, it was shown that the resistivity of grouted area by chemical grout decreased and the resistivity of the sand layer grouted by cement grout increased. |
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