Easter Glentore is a wind farm situated between Glasgow and Edinburgh. This project entailed the jacking of two substation transformer units back to their original level.
The very poor ground was a mixture of soft undisturbed peat along with 5.5m of infilled stone that had over a period settled and caused the substation units to subside on one side. The movement of these units, both weighing in at around 12t was putting the underground electricity cables which are fed from the wind turbine at risk of damage.
ABC Anchors were asked to install screw piles along the subsiding edge of both substation units and bring them back to level using underpinning jacking brackets.The project needed careful planning due to the potential damage to the underground cables during the pile installation and the cost of having the wind turbine shut down for longer than necessary.
As always with the underpinning process, careful excavation to expose the footings was the first operation. The units were both set on 300mm thick concrete slabs so once the underside of these had been exposed localised pockets could be cleared away under the edge of the slab to allow for the jacking plates. The piles could then be installed using the ABC 500X torque head mounted on a 5t excavator. 4 piles were used on the smaller unit and 7 and the larger one. All the piles needed to be installed to 4kNm of torque which meant they were 6m deep in order to penetrate the hard undisturbed layer which started at 5.5m.
Once all the piles were in place the jacking brackets could be fitted and the jacking up process could begin. Care is always taken during this process to ensure the structure is loaded equally and no damage is incurred.
40kN hydraulic jacks were used on each pile making the leveling of the units a simple operation. With the piles all preloaded equally and the units back to level the jacking brackets could be locked in place using the M16 threaded bars and the jacks removed.
Finally the excavated soil is replaced with a type 1 scalpings and compacted to ensure there is no movement between the piles and the foundation.
This was our first time using a screw piling system and I would highly recommend it, I would give the guys a 10/10!