Key construction techniques for Menghua heavy haul railway tunnels 并列题名：Construction technology of Mengxi-Huazhong heavy haul railway tunnel Construction technology of Mengxi-Huazhong heavy haul railway tunnel Key construction technologies for loess tunnel of heavy-haul railway 并列题名：Key construction technologies for loess tunnel of heavy-haul railway 并列题名：Construction technologies for eco-friendly asphalt pavement in highway tunnel