| 摘要 |
PURPOSE:To prevent any inadvertent accident, by a method wherein vibration is generated at the front of a shield excavator to detect a vibration elastic wave passing through a natural ground and the velocity thereof is computed to permit continuous survey of soil nature thereof. CONSTITUTION:A vibration is generated to a natural ground by a vibration generator 12 provided at the front of a shielding body 1 of a shield excavator 2 and a vibration elastic wave thereof propagating through the natural ground is detected with a wave receiver 14 provided at the center of a cutter head 4. The vibration elastic wave entering the wave receiver 14 is converted into an electrical signal and recorded into an electromagnetic oscillograph 19 after being amplified 18 while the transverse wave velocity of the elastic wave is calculated with an arithmetic unit 20 being allowed for the rotational direction and speed of the cutter head 4. The transverse wave velocity of the elastic wave is affected by the size, shape and compaction of soil particles of the natural ground. Thus, when a correspondence relationship is examined between the transverse wave velocity and soil beforehand, the nature of soil, namely, compaction of soil (standard petration value N), the particle size of soil (clay, sand and pebble) can be found along with the distinguishing between alluvial beds and diluvial beds, simply by checking the transverse wave velocity. |
