HE1851 B4069 Lyneham Banks Repair Wiltshire Council April 2024

B4069 Lyneham Banks Repairs

In 2022 significant a significant landslip took place on the B4069 Lyneham in North Wiltshire. The resulting landslip dislodged around 90m of the existing carriageway downslope. The B4069 has been closed since February 2022 when the landslip took place, movements continued throughout the first part of 2022 until slowing significantly during the summer months.

The B4069 is a regionally important route providing connectivity between junction 17 of the M4 and North Wiltshire as well as serving several local communities. The road when opened normally takes around 5500 vehicles a day.

It is proposed to stabilise the slope with a contiguous piled embedded retaining wall with capping and upstand at the top. The proposed structure will be constructed on the northern side of the B4069 with a length of approximately 109m.

A in-situ reinforced concrete (RC) capping beam will be supported on a single row of 600 mm diameter bored concrete piles. The in-situ capping beam will be 1000 mm wide and 1500 mm deep structurally connected with the piles. The capping beam will be connected to tension micropiles to provide additional lateral ground support to the retaining wall.

A vertical infill parapet or edge restraint is also considered to be provided at this location. The new parapet may be installed in the verge or attached directly to the capping beam at the back of the verge. Highway works will include reinstatement of the carriageway, pavement, drainage, and kerbs. To provide improvement to the existing highway drainage system, it is proposed that the highway shall be drained by a combination of gullies, carrier/ collector pipes and catchpits. The proposed highway drainage will outfall to a watercourse north of the B4069 via a new culvert.

To ensure effective drainage of the site a number of land drainage measures will also be put in place on 3rd party land either side of the B4069.

The works will be designed and built in accordance with current standards and guidelines, and will include for all key aspects of highway construction – piling, earthworks, carriageway, drainage, signage, and hard and soft landscaping works.