抄録
Dai-Shimizu Tunnel is the world-longest tunnel recently constructed for a bullet-train railway. Underground survey was conducted by two LaCoste and Romberg gravimeters G 210 and G 581 on June 4 and 5, 1982, This paper describes the outline of the gravity survey and the reduction procedures including terrain correction. The apparent density is determined as 2.04 g/cm3 by using the gravity-elevation relationship. The Bouguer anomaly is closely related to the geologic structure of the region. A negative anomaly is located on a massive quartz-diorite which forms extensively the mountain range, and a positive one on basic rocks in the northern half of the tunnel.
