HS2 finishes central section of 1.4 km Wendover green tunnel

What happened

The Wendover green tunnel lies in a cutting beside the A413 road, west of the town of Wendover in Buckinghamshire, England. It is designed to reduce noise and disturbance for people living nearby. EKFB, a joint venture of Eiffage, Kier, Ferrovial and BAM Nuttall, built it in two sections from opposite directions. On 5 October 2026 the last segment of the central structure was placed, joining the two halves for the first time.

Work on the segments moved quickly. Elton Qafaliaj, EKFB's project manager, said the first segment was installed in spring 2025 and more than 2,000 had been lifted in under 18 months. Building in two sections meant that excavation, segment placing and backfilling could all go on at the same time in different places. Umesh Gorasia, HS2 Ltd's project manager, welcomed the joining of the two halves.

Work is not finished. The portals at each end, the internal works and the backfilling remain. Ellesborough Road, which currently crosses the railway on a temporary bridge, also has to be realigned. Once each section is complete, earth will be placed on top so that the railway blends into the countryside.

Wendover is one of five cut-and-cover tunnels on the London to West Midlands part of HS2, along with Chipping Warden, Greatworth, Burton Green and Copthall. The project has about 105 km of tunnels in total, most of them bored deep underground. The 880 m Copthall tunnel at West Ruislip was the first green tunnel completed, in summer 2026.

The engineering behind it

A cut-and-cover tunnel is built from the surface. Engineers dig a trench or cutting, build the tunnel structure inside it, and then cover it with earth. At Wendover, more than 1.2 million cubic metres of material, mostly chalk, was dug out to form a level base. That material was stored on site and is now being placed back around and over the tunnel. In general, this method suits shallow routes where boring would be slower or more costly.

The tunnel's cross-section looks like the letter M. It is a double arch, with one half for northbound trains and the other for southbound trains. New Civil Engineer reported in January 2026 that each 2.5 m long ring is made of five precast pieces: two outer wall arch units, a central wall unit and two roof arch units. The central wall weighs about 46 tonnes, each outer wall about 36 tonnes, and each roof unit about 16 tonnes. Wendover has 548 rings.

The pieces are not bolted together. They lock in place through their shape, at pinned joints where the roof and wall units meet. An arch works mainly in compression, so the weight of the earth on top pushes the pieces together. This is why backfilling must be controlled. NCE reported limits on the weight of machines on the fill and on the difference in fill height between the two sides, so that the arch is loaded evenly.

The segments were made in a factory in the English Midlands and delivered lying down, then turned upright on site. Most were lifted in by crane. Under the temporary road bridge, where a crane could not reach, engineers used a self-propelled modular transporter with 16 sets of wheels to carry and place the pieces. EKFB says the precast method uses less concrete and steel than alternatives, which lowers embodied carbon.

What it means in Nepal

The sources do not discuss Nepal, so this section is about the methods and the skills. The first lesson is that not every tunnel needs a boring machine. Where a route is shallow, a cut-and-cover structure can be faster and cheaper, and covering it with earth can reduce noise and return the land on top to use. Choosing between bored, cut-and-cover and open cutting is an early design decision that engineers make with cost, ground and environment in mind.

The second lesson is the value of learning from earlier work. NCE reported that Wendover adopted more than 100 design and method improvements from EKFB's earlier green tunnels at Chipping Warden and Greatworth. These included prefabricating the reinforcement cages for the base slab, delivering concrete through the tunnels more efficiently, and testing whether larger backfilling machines could be used safely. Recording lessons and passing them on is a habit any site engineer can build.

The third lesson is about precast design. Every ring at Wendover uses the same five element types, although NCE reported that each piece differs slightly because the tunnel follows a curve. Making them in a factory allowed fast, repeatable work on site and closer control of concrete quality. Heavy pieces still had to be delivered, turned upright and lifted safely, which needs careful planning of cranes and access. The same ideas apply to precast culverts, bridge girders and building parts on much smaller projects.