WEST MIDLANDS M-SHAPED DOUBLE ARCH STRUCTURE

Requirements

We are currently on a job in the West Midlands that requires hydro demolition to an m-shaped double arch structure that has sustained micro-fracturing due to stress loading, which makes this a major contender for water jetting.

The job consists of cutting concrete to the structure of an underground tunnel.

Hyrdodemolition

The nature of water jetting enables exposed cracks running through the large pre- cast sections caused by tensile loads being applied during transit, to be accurately chased. This leaves a suitable well-formed key finish with all reinforcement remaining in-tact, allowing for a repair to be completed.

To minimise the impact on the local area we used ultra-high pressure water jetting (UHP) as this uses half the amount of water volume per hour compared to UHP, therefore half the amount of water requiring to be disposed off-site.

From our experience UHP is good for the environment, paint & coating removal.

However, our findings were that the increase in speed of water produced by the UHP whilst reducing the flow made it difficult for the operative because the UHP water jet is so fast (700 m/sec) it generates huge amounts of steam, this caused huge visibility issues within the tunnel environment and the client was expecting extremely accurate cutting because of the huge cost of the concrete sections.

So, we opted to change the jetting machine to high-pressure, which worked well and allowed the operatives to be in control and complete more locations per shift with the slower speed of water. In addition to this the increase in flow helped the water flow through the exposed cracks allowing for a clean precise cut. Although the volume of water being used per hour nearly doubled, the overall daily locations getting completed doubled too and this approach for the operative was agreed to be a significantly better result.

This method ensured the works program remained on time and continued to do so throughout the works.

All waste water used for the operation was pumped into IBC’s which were then emptied by an environment safe tanker unit and taken off site for disposal.