Abstract: Excavation controlling is a key technique in the process of large-section underground excavation, we can not only reduce costs of follow-up construction, but also enhance security if we control the underground excavation well. Selecting equipments of drilling holes, controlling the holes precision and refinement of charging are researched into and practiced in a large-scale underground powerhouse of Three Gorges project. Good results show that we can work additional 8.5 cm for the roofs and 5.3 cm for the sidewalls than standard in average, and control the extra-mining of cantilever crane beam in 2 cm, much lower than 20 cm which is the standard of criterion. The flatness of excavation is less than 10 cm, and the half holes rat of blasting is more than 95 %. A breakthrough in the controlling of forming quality is achieved, and it is highly value able in application. This paper will analyze and aggregate the specific process of controlling to provide example for similar projects.

Key words: large-section underground excavation, controlling the quality of forming shapes, Three Gorges project, application