METHOD AND SYSTEM FOR DETECTING COLLAPSE OF NATURAL GROUND IN SHIELD DRIVING METHOD

摘要

A method and a system for performing measurement by the resistivity method in order to detect the thickness of a sludge layer on the outer periphery of a shield machine. A reference resistivity on the outer periphery of the machine is measured by a row of the Wenner electrodes (14) to thereby detect the resistivity in the direction of the depth of the natural ground and the thickness of the sludge layer. At the same time, voltage distributions in the direction of the depth of the natural ground and in the direction of the arrangement of the electrodes are measured by a row of the dipole electrodes (16). Ratios of measured values by the dipole electrodes to those by the reference Wenner electrode row are obtained, to thereby form a distribution. Values equal to one another on a chart of this distribution are plotted by a continuous curve to obtain a contour line-shaped picture image, so that a shape of collapse of the natural ground can be recognized. This may be displayed two-dimensionally or three-dimensionally through image processing. Furthermore, a plurality of sets of the electrode rows (14, 16) are provided in the circumferential direction of the shield machine, whereby a resistivity is detected while electric currents different in frequencies are supplied, so that a collapse of the natural ground can be quickly measured.