Builders from China Railway No 4 Engineering Group Co Ltd dig the main tunnel of the No 1 bid in Gansu province as part of the Xining-Chengdu Railway, finishing 8,820 meters of digging, or more than half of its excavation work. With an estimated investment of 58.3 billion yuan ($8.21 billion), the railway will run for over 533 kilometers, linking major cities in Northwest and Southwest China upon completion.