8:00–9:00pm placement of downstream end and final 3 upstream culvert sections
The 1.5m box culvert sections were crane lifted in and laid on the compacted granular backfill to the precise, g.p.s. specified line and laser-proven grade and depth. The bedding design for the box culvert was designed by the Opus Engineer, who is knowledgeable about the River Bealey riverbed ground conditions, which thereby ensured a successful installation.
The proper installation of precast concrete box culvert typically starts at the downstream end and works back up stream with the culvert spigot end facing downstream and the bell end facing the upstream side. Variance from this norm was required to ensure the centre section of the culvert conformed to the precise depth beneath the rails specified. Once the centre section was accurately placed, installation proceeded first downstream, then upstream of the centre. These installation practices were consistent with the engineer’s design assumptions.
Overview of the under-rail culvert installation
These culverts are one component of a package of civil works that TruLine is delivering to their client, Hawkins Infrastructure. The Mingha Bluff Realignment is of a section of State Highway 73 within Arthurs Pass National Park between Mingha Bluff and Rough Creek, just to the East of Arthurs Pass village. This is is a narrow, winding section of road that threads through dense mountain beech rainforest. It is a challenging section of road to drive because it consists of two opposing lanes which have a series of very tight blind corners, leading to poor visibility and other objective risks, like narrow sections between steep bluffs and drop-offs. To manage the objective risks the Mingha Bluff section of the highway demands high levels of care and attention from all road users. In many places the two-lane road is so narrow it has no shoulder.