Cleeve Hill Slope Stabilisation

The project comprised of the slope stabilisation of the B4632 Cleeve Hill, 5km north east of Cheltenham.

Since 2014, ongoing deterioration of the B4632 had resulted in tension cracks and subsidence developing across both lanes of the carriageway. Drainage investigations also indicated that the sewer underlying the carriageway was becoming increasingly damaged by the slope movements.

Resurfacing had been undertaken on a yearly basis to keep the carriageway open, therefore, remediation was considered the only option to reduce maintenance costs and to permanently remove an ongoing carriageway safety defect.

Gloucestershire County Council (GCC) were keen to avoid a road closure, minimising disruption to the public. Working in ECI with the designers, our solution comprised of the use of small construction plant which could operate under a single lane closure of the northbound carriageway, with the southbound carriageway remaining open for the duration of the works.

To work around the site constraints, we worked with the design team to provide an innovative micro pile remedial solution which comprised 100 x 15m long micro piles, installed at 1m centres vertically and at an angle of 15 degrees. The heads of the micro piles were cast into a continuous reinforced concrete capping beam, installed below road level.

In addition to the piling works, the project included the installation of an Aco kerb drain, replacement of existing gully covers and full depth reconstruction and surfacing across the full carriageway width to incorporate a geotextile matting and erection of a new post and rail fence.

During construction, the presence of a BT duct in poor condition was located clashing with the proposed ground beam in several locations. We worked closely with the client’s design team to design a narrower beam with additional piles, in doing so the reinforcement for the original design could still be used.

The original plan was for all material excavated to be removed from site. However, several residents expressed an interest in recycling the surplus fill. We assisted these residents in obtaining U1 exemption certificates through the testing of the granular materials prior to delivery to their properties.

Following completion, Jennifer Dorman GCC’s Senior Infrastructure Engineer said “The geotechnical remediation works at Cleeve Hill in Cheltenham were complex, they involved the installation of an intricate piling design within a tight site, adjacent to live traffic. The work was finished on time and programme to a good standard. On such a busy section of road subject to traffic management for an extended period of time we were anticipating animosity from the local residents and road users, however the community engagement undertaken by the team ensured that everyone was up to date with progress and the team received written compliments from the local residents.”

The project was a finalist in the Ground Engineering Awards 2019 in the UK Project with a Geotechnical Value of up to £1m category.

Despite the challenging design and site constraints, we delivered an innovative solution which provided good value to GCC and was completed on programme, within budget with no outstanding defects upon completion.