Continuing a string of successful high-profile contracts in the Irish Republic, Groundforce is currently providing temporary works solutions to a new landmark office development in Dublin.
The company is supplying its heavy-duty MP250 and MP375 modular hydraulic props to main contractor Walls Construction to support the basement excavation for 1 Adelaide Road, a new office building just north of Dublin’s Grand Canal.
The 10-storey building is being erected over a two-storey basement constructed within a single large excavation measuring approximately 70m x 50m.
The excavation is lined with concrete secant piles and a capping beam which was completed in June this year. Walls Construction then commenced excavating down to B-2 level, with the Groundforce props installed at the capping beam level.
Groundforce has supplied its MP250 and MP375 props, configured with either 610mm, 813mm or 1220mm diameter intermediate-to-large extension tubes, depending on the span and loadings imposed.
The design loads for the propping range from 250–300kN/m, placing them in the mid-to-high range compared with typical projects. Due to the required prop spacing and lengths, MP375 props with 813mm tubes were specified to achieve the necessary performance.
The longest prop on the scheme is an MP375 spanning more than 41m across the widest part of the excavation. The shortest is an MP250, installed as a knee-brace across a corner and spanning barely 3m.
Cast-in shear studs and concrete cores were incorporated to manage the shear forces generated by the props. Three of the props were fitted with load monitoring pins at the client’s request. This allows for close monitoring of prop loads which, in conjunction with the use of wall inclinometers, provides additional assurance on excavation stability and deflection control.
Groundforce was engaged at an early design stage, before the capping beam was cast. This early collaboration allowed consulting engineer Arup to make efficiency gains by incorporating the propping forces and stiffness into the capping beam design.
Once Walls Construction has cast the B1 slab the Groundforce props can be removed to allow construction of the core walls and ground floor slab.
Groundforce design engineer Ahmed Adayem says: “The main challenge on this project arose from the irregular shape of the excavation which created complex shear forces at the retaining corners with shorter walls.
“We carried out several design iterations to optimise the layout and minimise these forces. Ultimately, a longer cross prop (the 41m-long MP375) was introduced to redistribute loads and reduce shear forces generated from two shorter props that meet at a corner, resolving the issue effectively.”
Groundforce’s strong track record in Ireland, where it has already delivered several similar schemes, played a key role in securing the project. The company’s emphasis on customer service, excellent equipment availability and local supply also ensured a smooth mobilisation, as Walls Construction’s project manager Conor Buckley affirms:
“I personally have not worked with Groundforce previously, but I am sure Walls will be working with them again soon. I would be very happy to – they have been a pleasure to work with. They are very proactive and readily available to assist with any design or onsite issues or queries.”
