PURPOSE: To quickly meet the condition of excavation by a method in which the image of a stratum which appears on a lens made of a wear-resistant material having a small frictional coefficient, set on the tip a rod, is observed by a fiber scope.
CONSTITUTION: When a rod 1 is penetrated into natural ground B from a cut- faced side A by means of the oil pressure of an excavator 5, the images of strata appear in sequence on a lens 3 on the tip of the rod 1 as the rod 1 is penetrated into the ground. Since the lens 3 is made of a wear-resistant material having a small frictional coefficient, the soil adhered to the lens 3 is separated from the surface of the lens 3 without causing any damage to the lens 3 and also without interrupting the observation of another stratum. The image of the stratum which appears on the lens 3 is sent out from the end face 2a of a fiber scope 2 to an observatory section 4 where the quality of soil can be soon judged. The conditions of excavation can thus be soon met.
OGATA KOJIRO
MITSUYANAGI NAOKI
