Essex groundworks contractor CJM has used a combination of Groundforce’s MP50 and Maxi Brace modular supports in a complex excavation in Nottingham.
The contract was for the construction of a new residential block in St Marks Street for client Elory Student Accommodation.
In order to reduce the temporary works requirement, CJM opted to construct the building’s two-storey basement in two phases, propping one side of the excavation until that half of the basement slab had been cast, then leap-frogging the supports to the other side and starting again.
The contract to supply temporary supports was keenly contested, with a local firm proposing the use of its proprietary mechanical props. Groundforce, however, offered its MP50 props with Maxi Brace beams, both of which are extended and pre-loaded hydraulically.
“Our props were lighter and easier to handle,” comments Mus Jiad, major projects engineer with Groundforce. “Not only are they easier to install, but being hydraulic they are quick to extend. Basically, using our props just speed everything up,” he adds.
Because the basement was excavated in two halves, the MP50 props could not span the full width and bear against the contiguous piled retaining wall on the opposite side of the basement. Instead Mus – working with consulting engineer JPE Contracts - proposed using massive concrete thrust blocks, each measuring 2m x 2m, cast into the ground to provide resistance to the lateral forces.
“We have worked with Groundforce many times previously, but what really swung it on this job was their can-do attitude,” says Jeff Salisbury, CJM’s site manager. “The other supplier only seemed to see problems with our proposed method, where as Mus saw it as a challenge and rose to the occasion,” he adds.
Phase 1 of the contract required nine of the 50-tonne capacity MP50 props and four thrust blocks; Phase 2 will employ four or five MP50s and one thrust blocks. The concrete thrust blocks will be broken out and removed after the permanent lateral support is in place.
One remarkable aspect of the project is that all the site staff employed by the main contractor, London-based Eguizabal Construction, are profoundly deaf.
“This could be seen as an extra challenge when it comes to site safety, but not so” says CJM’s Jeff Salisbury. “and choosing a support system that can be installed quickly and easily really helps”.
Thomas Salomone, managing director of Eguizabal comments:
“CJM said they would be using Groundforce for the temporary works as they come highly recommended. I was pleased to see the well organised mobilisation of the props on site, I observed the Groundforce props being installed and thought they were well designed and straightforward to install.”