Aerial photo taken on Aug. 6, 2019 shows 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 on Monday after over three years of construction work. (Photos: Xinhua)

Aerial photo taken on Aug. 6, 2019 shows 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 on Monday after over three years of construction work.

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 on Monday after over three years of construction work.

Aerial photo taken on Aug. 6, 2019 shows the New Baishatuo Tunnel (L) 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 on Monday after over three years of construction work.

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 on Monday after over three years of construction work.