Aerial photo taken on Aug. 6, 2019 shows a ceremony held to mark the completion of the New Baishatuo Tunnel in Fuling District of southwest China's Chongqing. The 10.004-km tunnel along the second railway line connecting Chongqing and Huaihua of central China's Hunan Province completed Monday after over three years of construction work. (Xinhua/Wang Quanchao)

Workers are seen inside the New Baishatuo Tunnel in Fuling District of southwest China's Chongqing, Aug. 6, 2019. The 10.004-km tunnel along the second railway line connecting Chongqing and Huaihua of central China's Hunan Province completed Monday after over three years of construction work. (Xinhua/Wang Quanchao)

Aerial photo taken on Aug. 6, 2019 shows a ceremony held to mark the completion of the New Baishatuo Tunnel in Fuling District of southwest China's Chongqing. The 10.004-km tunnel along the second railway line connecting Chongqing and Huaihua of central China's Hunan Province completed Monday after over three years of construction work. (Xinhua/Wang Quanchao)

Workers are seen inside the New Baishatuo Tunnel in Fuling District of southwest China's Chongqing, Aug. 6, 2019. The 10.004-km tunnel along the second railway line connecting Chongqing and Huaihua of central China's Hunan Province completed Monday after over three years of construction work. (Xinhua/Wang Quanchao)