Improvements to M271 J1 for Lidl Redistribution Centre
Stuart Michael Associates
- HD22/08 compliant: Statement of Intent, Preliminary Sources Study Report and Ground Investigation Report, Geotechnical Design Report
- Ground Investigation
- Embankment Widening Design
- Reinforced Earth Design
- Slope Stability Analysis
- Advance Direction Sign Foundation Design
Phase I and Phase II Ground Investigation
Under a Highways England S278 agreement, the construction of a new Lidl Redistribution Centre at Nursling near Southampton required major improvements to the M271 Junction 1 roundabout and slip roads. As part of the improvement works, CGL was commissioned by the client to undertake a ground investigation and produce DMRB HD22/08 compliant documents which included a Statement of Intent (SoI), Preliminary Sources Study Report (PSSR), a Ground Investigation Report (GIR), and a Geotechnical Design Report (GDR).
The scheme included widening of the existing motorway slip roads, the circulatory carriageway and side approach roads, in addition to providing new footpaths/cycleways around the junction. Lane closures were arranged through Highways England Managing Agent and Hampshire County Council to carry out the investigation which comprised cable percussion boreholes and trial pitting plus Dynamic Cone Penetrometer (DCP) Testing. Throughout the HD22/08 approval process, consultation and agreement was obtained from the Regulatory Authorities including Southern Gas Network (SGN) whose assets traverse the site.
Ground conditions comprised cohesive or granular embankment fill overlying River Terrace Deposits, on the Wittering Deposits. Accommodating the additional running lanes was achieved by widening the existing embankments around 6.0m high, with a combination of granular fill extensions and reinforced earth for slope gradients greater than 1v:2h.
As part of the main works, CGL undertook slope stability analysis for the embankment widening earthworks design, and bearing assessment calculations for new Advanced Direction Signs (ADS). All design and analysis was undertaken in accordance with Eurocode 7 and the UK National Annex and relevant highway guidance for design.
On the instructions of the client, CGL will also produce the HD22/08 Geotechnical Feedback Report (GFR).