MGF supports water pipework infrastructure beneath HS2 line

  • Project Burton Green
  • Client Severn Trent Water
  • Contractor J Murphy and Sons Ltd
  • Project Lead Lee Womersley, Engineering Manager
  • Key Benefit Using an integrated structural solution to overcome complex challenge underneath HS2, whilst minimising disruption to the network and ensuring protection of the network
Using an integrated structural solution to overcome complex challenge underneath HS2.

Introduction

HS2 will be the UK’s zero carbon, high speed railway, which has been taking shape for the last three years. This major initiative is the largest ever rail investment to have been made in the UK and the biggest infrastructure project in Europe.

Given the scale and significance of the project, MGF has a dedicated Rail/HS2 Team, who are on hand to provide expert help and guidance in relation to HS2 enquires and any associated rail infrastructure sector temporary works.

MGF was invited by Contractor, J Murphy and Sons Ltd, on behalf of Severn Trent Water (STW), to provide a temporary works solution associated with works done in preparation for the construction of HS2.

Temporary excavation support was required to enable a proposed under track crossing to be installed beneath the new HS2 line.

Due to the location of the proposed new pipelines, there was an existing water main crossing the proposed path that needed supporting whilst the new pipelines were installed.

The unsupported section of pipe was approximately 12m long, however due to the angle of the existing pipe in relation to the new pipeline, the exposed service required support over an 18m clear span.

In addition to the service support, there was a requirement for a 20m x 5.7m x 5.0m deep excavation to facilitate the installation of the new concrete pipe sections, directly below the service support.

It was not possible to install sheet piles where the existing service entered the excavation. An alternative support system was therefore required over a width of approximately 3.5m around the pipe entrance.

Traditional timber lagging was not suitable due to the distance between the primary supports. A more robust solution was necessary to resist the resultant earth pressures from the cofferdam and additional reaction loads from the service support system.

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“This scheme presented us with the opportunity to not only showcase our excavation support capabilities, but also the Lifting and Safety and Structural Support aspects to. All of this was on a section of the largest infrastructure project in Europe, and working alongside a valued customer.”

HS2 Project Manager, Tom Hughes

The Solution

A two-stage excavation support system enabled concrete pours to be progressed. A modular 305UC Brace with twinned 300 series struts at mid-span to maximise the digging window around the upper frame were specified, with 4N° Bays, comprising a back-to-back 254UC Brace being specified for the lower frames, which facilitated the pour sequence.

A King Pile System was constructed at the point where the service support entered the excavation. MGF trench sheets were installed horizontally between the king piles to sufficiently help transfer the earth pressures into the primary king piles. This design made sure there were no clashes with the existing pipework above.

Due to the deflection limits, a modular Warren Truss was designed in-house by MGF’s Engineers, using its versatile proprietary UniShore system. Standing at 1.7 metres tall, the truss spanned the full distance between the supports and was pre-assembled at the side of the excavation.

A cradle frame was also designed to protect the existing service from accidental impact during excavation works. To support the onsite team with lifting the prebuilt truss into place our lifting division specified and supplied the Contractor with one of our 6m S80 modular spreader beams.

                                                                                                                      


Our shoring, structural support teams and lifting division all came together to develop and deliver an integrated solution that met the stringent deflection criteria of the existing service, and the installation requirements from the permanent works. Our in-house Engineers leveraged their extensive experience and expertise to meet the requirements of the brief,” explains Lee Womersley, Engineering Manager. 

This highly integrated approach is testament to our industry-leading capabilities and has delivered proven results on multiple occasions.”

Lee Womersley, Engineering Manager

The Verdict

By choosing MGF, J Murphy and Sons Ltd was provided with a fully comprehensive that overcame all of the complex challenges associated with providing the required temporary support.