The concealed structure existing above the tunnel is very likely to induce tunnel geological disasters during construction. This paper introduces terrain correction technology based on orthogonal projection method and high power supply voltage technology with multiple electrodes laid at once into the traditional electrical sounding method to improve it. In addition, the improved electrical sounding method is applied to the detection of the concealed structures of long and deep buried tunnel. The exploration results fully reflect the spatial distribution of concealed structures and show good consistency with the drilling results. This study shows that the improved electrical sounding method can effectively detect the change of resistivity of geological bodies along the survey line profile, and can accurately identify the scale and location of concealed structures, thus providing a basis for tunnel safety construction and tunnel geological disaster prevention.
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