Project Brief

East West Rail Phase 1 is a £320M project to rehabilitate a 16km section of railway between Oxford and Bicester from a partially derelict branch line to a modern 100mph twin track railway. The project involves the stabilisation and widening of the existing rail earthworks formed in the 1850s and reduced to a poor condition since the Beeching Cuts of the 1960s.

Project issues

•    Widening and lowering of the track corridor was required to accommodate the new twin tracks and future OLE.

•    Noise Barriers were required at the crest of the slope to mitigate adjacent residential properties.

•    The existing slopes were identified by Network Rail inspections as potentially unstable

•    Design solutions were constrained by the existing boundaries.
 

Atkins assessed the geometry and ground condition of the existing cutting. This identified variable, over steep slopes and a shallow weathered layer within the cuttings that was causing stability issues. It was determined that retaining walls or a similar support system would be needed to achieve the proposed track layout and levels.

An extensive phase of optioneering was undertaken with the client and contractor to identify and develop a best value solution. Gabion baskets had proven slow and difficult to build on another part of the project.

The chosen solution involved installing propriety modular retaining wall units (Redi-rock) to create the required space. The wall design included an asymmetric alignment to provide flexible positioning of future OLE and box-out features for lineside equipment.

Solution

Marshalls Civils and Drainage designed a solution for the embankment wall in Cobblestone face walling which Network Rail and Atkins approved for use. However, project changes were made during construction, which lead to the further designs of walling by Marshalls, using engineering Redi-Rock engineering analysis software and approved by Atkins.

Due to the ease of which the walling solution can be installed, the delivery schedules were altered demonstrating the flexibility of system.

Clients Comments

Barry Mullen, Project Manager for Carillion Buckingham JV said “The assistance we have had from Marshalls Civils and Drainage with the Redi-Rock walling, from the sales team liaising with site schedules, to the patience of the Design team has really been appreciated.”

The use of the precast concrete modular gravity Redi-Rock wall provided a cost effective and aesthetic solution that was rapid to install on a congested site. The precast modular wall allowed for local remodelling around existing features such as bridge abutments.