抄録
This report is describing about the applicability of the Micro Gravity Survey Method for investigating abandoned mines, and about results of adopting tunnel stability measures for the Akita Highway's Sennin Tunnel Prject. The tunnel consists of a main tunnel (L=2, 503m, A=87m2) and an evacuation tunnel (L=2, 503m, A=18m2). Geological structure of the tunnels consisted of relatively hard rocks such as hard tuf, andesite, and tuffbrecia.
The NATM short bench cut and the NATM full face method using cut and blast were employed for excavating each tunnel. When the tunnel excavation reached around 580 meters from the entrance, large unexpect cavern emerged after small collapse of the cutting face. a result of detailed survey, the cavern was proven to be an abandoned mine. The Micro Gravity Survey Method was employed for investigating the cavern because the method was desirable for investigating wide space, and did not require test boring.
