Project Milton Keynes

We were called in by the Main Contractor during the construction of a large distribution warehouse, for advice on the stabilisation of the site boundary adjacent to a public highway. Once the groundworks on the site were underway it was realised that the original design, for a timber crib wall, to stabilise the boundary was no longer viable due to the temporary works that would be required to support the highway during construction and our advice was sought due to our previous dealings with the site team. A soil nailed slope with mini gabion facing was proposed to provide minimum disruption during construction and provide an aesthetically pleasing finish with no long term maintenance requirements.

Once the design was underway further constraints were identified with the presence of a high voltage cable within the highway boundary adjacent to the site. Discussions were undertaken with all parties involved, including several meeting with the electricity supplier, to establish what restrictions this imposed and to agree a viable solution for the upper section of the slope adjacent to the cable.

The final design included the installation of anchors in the upper slope with strict limitations on their length and additional safety precautions included within the installation methodology, discussed and agreed with the electricity company.

Design restrictions were also imposed due to the proximity of the highway and the associated required design life of the slope components.

Due to the site works already ongoing the programming of the works was critical and the build had to be undertaken over the winter period with the top section of the slope stabilised prior to the Christmas break.

Once we mobilised to site the bank was trimmed in sections from the top down to the required angle, leaving adequate material to provide a working platform from which the soil nails and structural mesh could be installed.

The final trim of the top section of the slope uncovered serious water issues, not previously identified by the site investigation or the groundworks already ongoing. The presence of old land drains, with a continuous flow of water the origin of which was never fully identified, required emergency works to be undertaken to intercept the water and divert it away from the stabilisation works to protect the bank during construction. The installation of adit drains in the final slope was also designed to intercept any water present within the slope. A series of drainage works was designed and installed within the gabion facing to intercept the land and adit drains to allow them to be connected into the permanent site drainage.

 

The design and installation of the drainage works of the drainage works and additional soil nails/anchors required to stabilise the bank in the areas where the water was encountered was carried out without delay to enable the works to progress in a timely manner and to prevent any additional degradation of the cut slope.

 

The original build methodology would have enabled us to construct the stone mattress facing as the works progressed however, due to the water issues and requirement to install additional drainage in the slope, the facing was constructed from a MEWP with man basket after the full extent of the slope had been stabilised.

 

With full cooperation between the site and design team the works were completed to prevent any delay to the other construction teams on site.