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Mole Man’s underground tunnels filled

Around 500m3 of foamed concrete from Propump Engineering was used to stabilise the property of a pensioner known as “the Hackney Mole Man”, after he spent 40 years digging a network of tunnels beneath his home.

William Lyttle, who owned and lived inside the £1m Victorian property at 121 Mortimer Road in Hackney, east London, was evicted from the 20-room detached house for his own safety. It was after the council discovered he had shovelled out 300m3 of earth to create a ‘basement’ beneath his garden area and a further 200m3 in tunnels. Using ultrasound scanners it was revealed he had hollowed out a labyrinth of tunnels and caverns, some 8m (26ft) deep, spreading up to 20m wide.

The tunnelling works started off as a simple wine cellar but the Mole Man’s ambitious plans grew to include a leisure centre, gymnasium and a sauna. The engineers found the foundations of the four-storey house shored up with makeshift scaffolding poles and pit props as well as assorted items such as a fridge-freezer and a bath.

After contact with Hackney Council, Propump Engineering was asked to visit the site and provide an assessment on the feasibility of infilling and stabilising the property using a specifically designed foamed concrete. Ironically, the council required that any infill material used to stabilise the property be easy to re-excavate. With its high air content, foamed concrete was the ideal solution.

The material needed to be lightweight, pumpable, highly plasticised and capable of being placed quickly. The foamed concrete was pumped into the property over a five-day period, with the final foamed concrete design having a cement content of 220kg/m3, a plastic density of 1100kg/m3, and a 28-day compressive strength of 1.5MPa.

Working with engineers from Hackney council, an abandonment infill scheme was devised whereby a staged pouring procedure was adopted. This method allowed for certain unstable areas to be sufficiently treated and stabilised, and after the foamed concrete had cured, allowed safe access into these areas for pump and vent pipes to be installed. Foamed concrete was then pumped through these pipes to complete the stabilisation process.

All the foamed concrete was manufactured on-site using a mobile, inline foaming and pumping system, the design of which is an ideal mechanism for pumping foamed concretes over long distances, with no loss of air content. These systems accept full deliveries of base material (sand, cement and water) and process them, on a continual basis, into the specified foamed concrete.

This extremely efficient method of making foamed concrete provides a significantly more economic and environmental approach in comparison to other methods of foamed concrete production.

Lyttle, from Ireland, died aged 79 earlier this year. An eccentric who endeared himself to his neighbours in spite of his digging, he never revealed the motivation behind what he called his “home improvements”.

Following his eviction the pensioner was put up in a hotel for three years while the council found accommodation for him. After being rehoused in a flat in St Lawrence Court in de Beauvoir Estate in June 2009, Mr Lyttle continued his activities and it is believed he left a hole in a wall within the flat.

The hunt for possible heirs of Lyttle, who could be in line to inherit £700,000 from the sale of the house in Hackney, goes on.

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