the boring machine of the mont cenis tunnel (the fréjus rail tunnel) - 隧道鑽掘機 幅插畫檔、美工圖案、卡通及圖標隧道, 地底下, 19世紀風格
tunnel construction using the pneumatic working method — workers operate inside a pressurized shield chamber supported by heavy timber beams - 隧道鑽掘機 幅插畫檔、美工圖案、卡通及圖標