Photo taken on June 27, 2018 shows the inside scene of the Ban Nakok Tunnel in northern Laos' Oudomxay Province. Ban Nakok Tunnel of China-Laos railway, constructed by China Railway Guangzhou Engineering Group Co., Ltd, has broken through over 1,000 meters on Wednesday. (Xinhua/Liu Ailun)

Photo taken on June 27, 2018 shows the construction site of the Ban Nakok Tunnel in northern Laos' Oudomxay Province. Ban Nakok Tunnel of China-Laos railway, constructed by China Railway Guangzhou Engineering Group Co., Ltd, has broken through over 1,000 meters on Wednesday. (Xinhua/Liu Ailun)

Photo taken on June 27, 2018 shows the construction site of the Ban Nakok Tunnel in northern Laos' Oudomxay Province. Ban Nakok Tunnel of China-Laos railway, constructed by China Railway Guangzhou Engineering Group Co., Ltd, has broken through over 1,000 meters on Wednesday. (Xinhua/Liu Ailun)

Photo taken on June 27, 2018 shows the construction site of the Ban Nakok Tunnel in northern Laos' Oudomxay Province. Ban Nakok Tunnel of China-Laos railway, constructed by China Railway Guangzhou Engineering Group Co., Ltd, has broken through over 1,000 meters on Wednesday. (Xinhua/Liu Ailun)