Abstract:

Superlarge karst caves are encountered during construction of Naqiu Tunnel on Yongji Highway. As a result，a combination structure of bearing pile foundation + vertical and horizontal framebeamplate structure + reinforced concrete retaining wall and slag backfilling are adopted based on characteristics and treating difficulties of large karst cave and theoretical and site studies. And then a set of construction methods of alternate updown construction of the structure on basis of slag backfilling is established. The construction practice shows that the technologies used are rational and feasible and good effect has been achieved.

Key words: Naqiu Tunnel, superlarge karst cave, bearing pile foundation, vertical and horizontal framebeamplate structure, reinforced concrete retaining wall, slag backfilling