Haruna Tunnel

Haruna Tunnel is a tunnel on JR East-Joetsu Shinkansen line in Japan that runs from Nakazato-cho, Takasaki city to Kawashima, Shibukawa city, in Gunma prefecture with approximate length of 15.350 km. It was completed and opened in 1981.
Excavation was extremely difficult due to the poor geology consisting of volcanic mud flow sediments and water inflow reaching a maximum of 110 t/min, so injection, two-stage silot, and pressurization methods were used in combination. The discharge of tunnel water also affected the ground surface, causing a decrease and depletion of well water, irrigation water, and surface water. In addition, on July 20, 1978, a 30-meter-wide cave-in occurred in the Yamakoda area of Haibuto-Mura. The fields and the Arai-Shimomurota line of Gunma Prefectural Road No. 154 were engulfed, and a large amount of earth and sand flowed into the tunnel directly below.