Groundwater lowering for construction of the Kilsby Tunnel on the London to Birmingham railway

This lecture will review the construction of the Kilsby Tunnel built in the 1830s under the direction of Robert Stephenson, which faced the problem of driving through 400 m of quicksand. The lecture will discuss route selection, geology, pumping, and construction methods.

The Kilsby Tunnel, constructed in the 1830s under the direction of Robert Stephenson, faced severe problems when a section of the tunnel, almost 400m long, was driven through water-bearing unstable ‘quicksand’ conditions. Contemporary methods were not well suited to tunnelling through such conditions, and in previous decades, several canal tunnels had been planned to specifically divert around expected ‘bad ground’, and others took years to complete at great expense.

Stephenson’s team, drawing on their experience from the mining industry, did not take this approach and ultimately worked through the unstable ground, albeit with considerable delays and cost increases. This was achieved in part by establishing a large-scale groundwater pumping system, unique for the time, that lowered groundwater levels and stabilised the quicksand, which resulted from a buried channel of glaciofluvial sands, cut into bedrock, that had been missed by trial borings. Steam engines were used to pump from multiple shafts (including four dedicated pumping shafts, off set from the tunnel alignment), with a reported pumping rate of 136l/s for several months.

The work at Kilsby was two decades before Darcy’s law established the theoretical understanding of groundwater flow. Despite the lack of existing theories, Stephenson used careful observations and interpretation of groundwater flow in the ‘quicksand’ to navigate the tunnel project to a successful conclusion.

Post-event food and drinks sponsored by Coffey Geotechnics, Stuart Wells, and WJ Group