In 1895 Glasgow was in the grip of a kind of tunnelling mania.
The Central Station low-level line was being dug, the underground railway circuit was nearing completion, and the Glasgow Harbour Tunnel Company’s pride and joy was about to be opened after five years of excavating under the Clyde. Flash-forward over a century and a section of tunnel, just outside Govan Station on the Glasgow subway system, was in a poor state, having been subject to water and sand ingress for many years. Add to this a failing in the tunnel system to reduce the problem and the result was proving costly and disruptive to maintain.
In a consultative process synonymous with WJ Groundwater, we worked with Keller to develop a permanent scheme to lower the groundwater level to below the tunnel invert level. To make thing s interesting, all of this was to be installed and maintained from outside the tunnel itself. Fortunately, the tunnel operator owned the land above the tunnel!
Initially, we built 4 shafts up to 15 m deep alongside the tunnels, from which 32 horizontal wells were drilled under the existing tunnels. And all of this activity was undertaken whilst the railway remained in operation.
To allow drilling of the horizontal wells below the tunnels in dry conditions, we installed a temporary surface deepwell system. This reduced groundwater levels and therefore minimised the risk of lost ground during the drilling process. The wells themselves were not actively pumped, but drained under gravity to the shafts, which were interconnected. Our analysis of the situation proved that the abstracted water would drain to the deepest shaft from where it is pumped, and then on into the existing sewage network.
Not only did our innovative solution to a century old problem succeed, but the WJ project team also won the prestigious Fleming Award for their ingenuity. Regarded as the premiere accolade for the geotechnical sector within the UK, WJ are extremely proud to have maintained the pioneering spirit of Victorian engineering in the 21st century!
- LOCATION: Govan, Glasgow
- CLIENT: Strathclyde Partnership for Transport
- MAIN CONTRACTOR: Keller