| 摘要 |
PROBLEM TO BE SOLVED: To precisely estimate the ground state in the front of the face of a tunnel prior to the excavation of the tunnel. SOLUTION: An electrode rod 13 having an electrode part 12 at the tip is extended in a casing rod 10, a horizontal boring hole 1 is drilled to a prescribed depth of the ground in the front of the tunnel face by the rotating propulsive force imparted to the casing rod 10. The mouth of the horizontal boring hole 1 is blocked by a mouth cap 14, and the inner part of the hole is filled with flowing ground water, and the electrode part 12 connected to an electric logging measuring device 20 set in the tunnel pit through the tunnel- side end of the electrode rod 13 is protruded into the boring hole 1 from the tip of the casing rod 10. Thus, the specific resistance of the ground is measured with a ground electrode 21 connected to the device 20 to perform the electric logging in the position of the electrode part 12. |
