The London Underground is one of the world’s oldest and most extensive metro systems. It serves millions of people every day, providing an efficient mode of transportation throughout the city. However, with the city’s population constantly increasing, the demand for better and more extensive transport networks has also increased.
To meet this demand, the London Underground is constantly undergoing improvements and expansions, with new lines being added and existing ones being upgraded. One of the key aspects of these improvements is the construction of new stations, as well as the expansion and upgrade of existing ones. Piling works play a critical role in this process.
Piling is a process of drilling or driving piles, which are long, slender columns of concrete, steel, or timber, into the ground to support structures like buildings, bridges, and in this case, underground stations. The piles transfer the load of the structure to the soil or rock beneath, providing stability and support.
Underground piling works at 16 Old Bailey
Piling works in the London Underground
Piling works in the London Underground stations are critical and complex, as they require the careful coordination of various teams, including architects, engineers, and construction workers. These works must also be carried out in a way that minimises disruption to the daily operations of the Underground, which can be a challenging task. One of the most significant challenges of piling works in the London Underground stations is the limited space available, as they are often located in densely populated areas with limited space for construction equipment and materials. Therefore, works need to be carried out using specialised equipment that can be easily transported and assembled in tight spaces.
Another challenge is the need to minimise vibrations and noise during the piling process. Underground stations are often located near residential and commercial areas, and excessive noise and vibrations can cause disruptions and inconvenience to nearby residents and businesses. Therefore, specialised equipment, such as silent piling rigs, is used to minimise noise and vibrations.
Additionally, the ground conditions in London can also pose challenges for piling works. London is built on a complex geology of clay, sand, gravel, and rock, which can vary greatly in strength and stability. Therefore, engineers must carefully analyse the ground conditions and design piling works that are suitable for the specific site conditions.
Despite the challenges, piling works in the London Underground stations have been successfully carried out for many years, enabling the construction of new stations and the expansion and upgrade of existing ones. The piling process is carefully planned and executed to ensure the safety of workers and commuters, as well as to minimise disruptions to the daily operations of the Underground.
Some recent piling works
There have been several recent piling works in the London Underground system. Here are a few examples:
Northern Line extension — the Northern Line extension is a new branch of the Northern Line that serves the Battersea area in South West London. Piling works for the extension started in 2016 and involved the installation of more than 1,000 piles, with works carried out using a variety of methods, including rotary bored piling, CFA piling, and driven steel tube piling.
Bank Station capacity upgrade — Bank Station is one of the busiest stations in the London Underground system, serving more than 50 million passengers each year*. To improve the station’s capacity and reduce overcrowding, a major upgrade project was undertaken. Piling works for the project involved the installation of 144 piles, with a length of up to 32 meters. The piles were installed using a silent piling technique to minimise noise and vibration.
Victoria Station upgrade — Victoria Station is another busy station in the London Underground system, handling around 84 million passengers each year**. A major upgrade project was undertaken to improve the station’s capacity and reduce overcrowding. Piling works for the project involved the installation of more than 300 piles, with a length of up to 25 meters. The piles were installed using a combination of driven and bored piling techniques.
Tottenham Court Road Station upgrade — Tottenham Court Road Station is a key interchange station in the London Underground system, serving the Central and Northern lines. To improve the station’s capacity and accessibility, a major upgrade project was undertaken. Piling works for the project involved the installation of more than 200 piles, with a length of up to 35 meters. The piles were installed using a combination of driven and bored piling techniques.
These are just a few examples of recent piling works in the London Underground system. Each project has its own unique set of challenges and requirements, but all are critical to the continuous improvement and expansion of the Underground network.
One significant aspect of piling works in underground areas is the amount of piling that has been done on the overground sections of the underground, many of which run on embankments and cuttings — piling works along the crest of these embankments to stabilise the railway. Also, there is a recent drive for step-free access meaning that lifts have been installed requiring piling to be undertaken. Crossrail is a new section of the underground which required masses of piling operations (along with tunnelling, grouting, etc.). Not enough mention of restricted access piling is our expertise at Deconstruct and we are very familiar with the works done in the undergrounds of London.Richard Hayman-Joyce, Deconstruct Piling Director
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*Estimate figures from 2019 by Transport for London, Bank and Monument station included.
**Estimate figure from 2019 by Transport of London.
Piling installation numbers according to OpenAI’s ChatGPT (OpenAI, n.d.)