Werrington Grade Separation

Case Study

Werrington Grade Separation

Client: Morgan Sindall
Location: Peterborough
Duration: May 2019 to June 2020

Project Overview

As part of Network Rails East Coast Upgrade to increase capacity. The Werrington Grade Separation involves the creation of a new two-track railway line under the East Coast line at Werrington, north of Peterborough.

Civils work by Morgan Sindall involved open-cut approach cuttings and a 155m long curved concrete jacked box tunnel.

Pressure Relief Wells

The project had complex ground conditions consisting of four confined aquifers. A dewatering design was established, which consisted of the installation of over 300no passive pressure relief wells upto 27m deep.

Part of the jacked tunnel works involved the placement of 2no x 2.85m Ø guide tunnels. In which passive pressure relief wells were installed, with working operations adapted, after risk assessments to work under COVID restrictions within a confined space.

Groundwater Monitoring

26no groundwater monitoring points were installed across the site. These consisted of grouted in Vibrating Wire Piezometers (WWP) that enable remote monitoring of porewater pressures at various levels. In addition to internal piezometers and external standpipes to enable monitoring of groundwater levels.

Siphon Haft Dewatering - Ejectors

An ejector dewatering system consisting of 14no twin-pipe ejectors, was installed around the external perimeter of 2no siphon shafts to reduce and maintain porewater pressures to below shaft excavation levels. Together with the installation of 8no internal passive pressure relief wells.