Update
The bill giving the go ahead to construct phase 1 of HS2 was given Royal Assent on Thursday 23rd of February.
This blog will focus solely on the construction and engineering involved, so I will leave a description of project and the political aspects of the planning to one side.
To begin with I want to explore how you go about altering the landscape in order to build a new high-speed railway that is as flat and straight as possible. With a maximum design speed of 400km/h (250mph) over the straightest sections of track it is important that the curve radius is long as possible, in the case of HS2 the minimum horizontal radius for 400km/h operation is 7200m.
Using knowledge gained from following other road and rail projects it's possible to examine how the new line will likely be built and the construction methods involved.
The closest recent parallel that I can draw upon is the construction of a new grade separated rail junction at Norton Bridge (Staffordshire), this project required the construction of 11 bridges and 9.6km of new railway.
Other parallels can be drawn from the construction of 7.5km of new dual carriageway connecting the M6 and M56 in Cheshire.
With both projects a large part of the work "simply" involved moving earth via moxy (articulated dump truck) from one part of the site to the other, although there was of course a systematic and very purposeful way in which this is done.
As with any large construction project the first stage will involve establishing compound sites along the route in which offices and staff facilities will be located and plant machinery stored.
Before any site clearance can commence the area within the site boundary must be free of protected species such as great crested newts for a number of weeks, during which time regular inspections must take place.
Once the site boundary is established (and free of newts) and compounds complete the next task is to begin preparing the land through which the line will be built. In rural areas this will involve stripping and storing the initial layer of fertile earth. The earth is stored close to where it was originally excavated from, this is so it can be returned back to the land once final landscaping commences.
In built up areas the initial phase of construction will involve demolition and site clearance. For HS2 this demolition will mostly take place around the Euston terminus and Birmingham station. In this part though I'd like to focus on the groundworks required in rural areas.
In rural areas the fertile earth is stored close to where it was excavated from, by doing this much of the ecology can be retained, this will help with the process of reestablishing wildlife habitats and returning agricultural land back to use.
A556 initial groundworks March 2015
The next phase of construction will involve deep excavation of cuttings and the building of embankments and structures. To do this excavators working in tandem with moxys will excavate and then move material from cuttings to areas where embankments will be built.
In this way it is possible to sculpt the landscape without having to move any earth off site by road or rail. Spoil from the excavation of tunnels can also be translocated to different parts of the site in this way.
Stafford Area Improvement Programme ground works.
The construction of a new grade separated junction at Norton Bridge is a good example how vast quantities of earth can be moved without the need to take any off site. In all 1 million tonnes of earth was moved in order to construct the 7.5km track and 11 bridges required for the project, yet non had to be taken off site.
This was achieved by creating a temporary road which extended along the length of the site, this haul road was then used to transport the material from where it was being excavated to where it was required. With 11 bridges constructed a lot of material was required in order to build approaches to overbridges. Earth was also used for landscaping either side of the line in order reduce the impact of the line on the landscape.
Of course for HS2 there will not a be a single 100km haul road, a project of this scale will be split up into sections, however withing each section it is likely that the same method of moving material will be employed.
A556 overbridge
The image above of a new overbridge constructed for the A556 project demonstrates where material is required in order to build new approaches. Earth was eventually built up on either side in order to build approaches for a new road overbridge.
It was suggested by a rural campaign group that millions of lorry loads will be required to take material off site by road, however the A556 and SAIP projects show that this needn't and will more than likely not be the case.
In part two I will discus the construction of bridge structures and look at how the impact on the existing road network can be minimised.
You can read part two here
