| 摘要 |
PURPOSE:To make it possible to decide a sign of a bedrock breakdown even by an unexperienced person easily within a short period of time. CONSTITUTION:A pair of power electrodes 3 and 4 are arranged to the upper part of a skin-plate 1 of a shield excavator at right angles to the direction of advancement through an insulator. Two pairs of detection electrodes 5a, 6a and 5b, 6b separated from each other at right angles to the direction of advancement are provided to positions on both sides of the direction of advancement at equal intervals, and voltmeters 8a and 8b are respectively connected to two pairs of detection electrodes 5a, 6a and 5b, 6b. A difference in measured values between both voltmeters 8a and 8b is calculated, and an operator 9 outputting an indication output on a displayer such as a display l0, etc., in the case the value is in excess of setting is connected to both voltmeters 8a and 8b. |
