By Lynda Myer
The British Tunnelling Society’s April lecture will focuse on the Kilsby Tunnel on the London to Birmingham railway, which is a historic tunnel. Mike Chrimes, vice-chair of the ICE panel for historical engineering works, and Martin Preene, technical director, Coffey Geotechnics Ltd, will discuss groundwater lowering for construction of this tunnel.
The responsibility of constructing the Kilsby Tunnel in the 1830s was up to Robert Stephenson, and it encountered severe problems when a section of the tunnel, around 400m long, was driven through water-bearing unstable quicksand.
Due to the conditions of the area contemporary methods were not well suited to tunneling, 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.
Despite considerable delays and cost increases,Drawing on their experience from the mining industry, Stephenson’s team, worked through the unstable ground.
By lowering groundwater levels and stabilising the quicksand, which resulted from a buried channel of glaciofluvial sands, cut into bedrock, that had been missed by trial borings, establishing a large-scale groundwater pumping system, unique for the time, was the reason of their success. Steam engines were used to pump from multiple shafts – including four dedicated pumping shafts, offset from the tunnel alignment – with a reported pumping rate of 136 litres per second for several months.
Although the work at Kilsby was two decades before Darcy’s law established the theoretical understanding for groundwater flow, Stephenson benefited careful observations and interpretation of groundwater flow in the quicksand to navigate the tunnel project to a successful conclusion.
On April 18 the ICE in George St, London W1P 3AA will host this lecture, which is a joint event with the British Geotechnical Association and the Engineering Group of the Geological Society. It is an in-person meeting, which will also be streamed live at here.
At this month’s meeting, on March 21, the three finalists for this year’s Harding Prize will present their papers.
