Sam Sherwood-Hale spoke to Mike Barker and Lloyd Williams, Project Director and Project Manager of RPS Group’s ground investigation work packages for HS2…
The UK’s largest ever ground investigation for the new High Speed 2 (HS2) rail link between London Euston and Birmingham Curzon Street is now in its fourth year. RPS has successfully delivered 13 of the original ground investigation work packages working directly for HS2 Ltd, the most of any company on the framework with the value of works completed so far totalling circa £5 million. The appointed main works and enabling works contractors are now undertaking supplementary ground investigation to support scheme and detailed design, including value engineering and RPS is currently delivering an additional three packages of works.
RPS has successfully delivered 13 of the original ground investigation work packages working directly for HS2 Ltd. What kind of logistical challenges did you and the team face?
The nature and scale of the scheme, divided into packages of works across the 140 mile long HS2 route, meant continuously working across land where numerous stakeholders were involved as well as responding to diverse ground conditions and vast quantities of varied geological data.
Our packages of works took us from central London where we had to ensure minimal disturbance to the 120,000 people that pass through Euston station daily, right through to rural environments in very snowy and wet conditions which required a different approach altogether.
For example, we faced a particular logistical challenge when access to one of the working areas required taking large plant along a privately-owned dirt track used by a local equestrian club. The track had several low-lying boggy areas and there was concern that plant movement would cause the track to become unsuitable for horses. RPS engaged with a quarry to supply material and local a contractor to undertake improvement works to the existing track as well as extend the track to the working area. This allowed the required ground investigations to be completed within a working week without causing interruption to the horse riders at the weekends.
How do you handle working across land where numerous stakeholders are involved?
Advanced planning is crucial to ensure the appropriate licences, permissions and approvals are in place. We have clear processes and flows in place to ensure these are all captured and programmed in to the works.
We manage unforeseen changes by working to a dynamic programme and scope with our team’s setup so we have the flexibility to move our mobile plant and drill rigs to different areas of the work packages at short notice; continuing the workflow while accommodating the requirements of land owners and other stakeholders.
How complex were the ground investigations? What sort of techniques did you have to employ?
It has been a uniquely complex ground investigation requiring a variety of techniques to deliver it. On site, we have utilised conventional and wireline rotary, cable percussive drilling, high pressure dilatometer tests and self-boring pressuremeter testing, sonic drilling and Cone Penetrometer Testing. We have also undertaken gamma, televiewer downhole and surface and downhole seismic testing as well as trial pitting and window sampling. Specialist geotechnical laboratory testing has been a core element of the scheme including complex and lengthy testing on over-consolidated clays, only able to be undertaken by a handful of UK laboratories.
The contract is divided into packages of works across the 140 mile long route, how did you arrange operating with local contractors?
We developed a framework of specialist and local sub-contractors, with all works managed and supervised by our team. Additionally, non-technical contractors including access plant vehicles have been sourced locally to the individual work packages through local farmers and businesses, supporting their workforce with the necessary HSE certifications.
How did you manage and distribute the data generated from the ground investigations?
That is definitely one of the main challenges encountered of a project of this scale. We developed a robust data management plan and quality management systems. Throughout the works we have: liaised closely with the logging software company; provided AGS4 and GI data management (HoleBASE) training to all project and site staff; resourced a large team of dedicated personnel to data management and data quality control; and provided training, guidance and workshops to some specialist contractors and laboratories that were not set up for reporting AGS4 data. HS2 Ltd presented our data management plan/processes and systems to the other GI Framework Contractors, exemplifying our best practice and to implement consistency in standards and approach to data across the whole of the project.
What are some specific tests your teams carried out?
While working in an area of a proposed large deep excavation associated with the redevelopment of Euston Station we undertook a specialist and rare test called a Self Boring Pressuremeter (SPB). This comprises a cylindrical instrument bored into the ground with increments of pressure applied through pumping water down the borehole and into the instrument. The test allows for in-situ measurements to be taken and geotechnical parameters of the soil and rock required for the design and installation of structures buried deep in the ground.
How did you handle collaboration with TfL, and other local governing bodies, when you required access to London Euston Station?
While working in London Euston Station we faced strict limitations on access, traffic management and control of construction noise. Before the works commenced we met with Camden County Council and agreed mitigations that would be utilised during the works to minimise the noise generated by our drilling. Planning for the works included our Project Manager attending and inputting into the Camden Traffic Liaison Group Consultations in conjunction with representatives from HS2. During the works we liaised closely with HS2 Ltd, Transport for London (TfL), London Underground, Camden Council and London Buses as well as the other HS2 enabling and main work contractors to ensure maximum collaboration and keep the works on schedule. This collaboration included both at the high level with the project managers and planners, but also our team on site were in daily contact on the ground with TfL, Network Rail and HS2 operatives working at Euston Station. Attaining drill rig access for some locations involved entry through the main TfL bus station at Euston. To ensure minimal disruption to the bus service, access was arranged during overnight operations.
How did that compare to the challenges you faced in the rural areas at the other end of the route?
The challenges faced in the rural environments were also unique. With drilling works being undertaken all year round, we faced winter conditions and very soft ground. We required widespread use of bog mats to get access and on occasion bespoke methods were required. On several occasions dedicated haul roads were constructed (a rarity for a typical ground investigation) and during the severe wet and snowy weather conditions in March 2018 a specialist sledge was used to transport the cable percussion drilling rigs.
How did the scope of the work change as the project was carried out? Did you have to change your approach in anyway?
Ground Investigations need to be adaptable to take into account the ground conditions encountered and to ensure the correct data is obtained for the design of the proposed cuttings and tunnels. The HS2 ground investigation was no different and adding to the challenge was the fact that some of the areas were not relatively well known in terms of drilling conditions. Notably the Tamworth area where the Hopwas Breccia and underlying Kidderminster Formation proved particularly challenging. The initial scope of work called for wireline geobore rotary drilling to progress these holes, however early on in the programme it became apparent that this wouldn’t work. The matrix material of the Breccia was heavily weathered while the clasts and cobbles contained in the weak matrix retained a lot of strength. The result meant it was a challenge even to progress the boreholes let alone carry out suitable sampling and testing. Immediate identification of the issue allowed us to quickly mobilise an alternative method, sonic drill rig, to progress the hole with minimal delay.
Let’s talk about your roles, how do they differ and what responsibilities do each of you have on a day-to-day basis whilst working on this project?
As Project Manager, Lloyd acted as the Liaison Engineer on the project between the numerous parties involved and was responsible for the quality, technical compliance of the acquired data and to deliver this on time and within budget. Lloyd coordinated with the RPS Site Manager to ensure that site work was progressing as expected, liaised with the Data Manager to ensure that data and documentation was up-to-date and accurate, closely liaised with the HS2 project team and along with the HS2 land access team, met with landowners and other stakeholders to agree access routes and programme for the works. Agreeing changes to the methodology and scope of work with HS2 to ensure successful delivery of the required data was also a large part of Lloyd’s day to day responsibilities. As the Project Director, Mike had overall responsibility for ensuring we were meeting our required technical and commercial performance on the contract. Mike ensured that the resources were available to successfully undertake the works and developed the Framework of specialist and local contractors, ensuring they were compliant with the technical, H&S and environmental requirements expected of them.
We’ve written previously about the skills shortage and how many rail engineers are set to retire over the coming years. HS2 is seen as an opportunity for young people to get into a career in rail, has that been your experience from what you’ve seen?
From a ground engineering perspective, it has been a massive opportunity for RPS’ junior consultants to be involved in a large-scale rail project. The scheme has exposed our teams to a wide variety of geological conditions and allowed excellent development opportunity with chance to rotate into different roles from technical, logistical and data management. A lot of our junior consultants and engineers have been exposed to some of the specialist techniques being used on HS2, so this project has given them the opportunity to be involved in the collection and reporting of that data.
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