Our Ground Engineering Article is Out!
We’ve been working hard on using cosmic ray muons for railway shaft detection for almost two years now and it’s nice when we start seeing results. Ground Engineering magazine is a peer-reviewed publication who have picked up our development, bringing it to the wider the community.
Background on 19th Century Shafts and the UK’s Railways
In the period between 1840 and 1900, the UK’s railways went through rapid expansion. In order to excavate the tunnels to support the strong railway growth, Engineers developed a method of digging out shafts along the line of a tunnel to speed up the whole process. When a tunnel was completed, some of the vertical construction shafts would be kept as ventilation shafts and others capped at both ends, possibly back-filled, and left assumed stable.
The 1953 hidden shaft collapse in Swinton, near Manchester, starkly illustrates that a lack of construction shaft identification and remediation can cause devastation for neighbouring populations and rail users. Hidden shaft investigations typically require intrusive drilling into the tunnel lining to locate voids and poorly backfilled shafts.
Intrusive drilling may cause instabilities and lining failure or, the outpouring of collected groundwater. Historical investigations using both intrusive (drilling) and non-intrusive (Ground Penetrating Radar) methods have been inconclusive, and often raise more questions than they answer. Drilling can be hazardous and costly as several drill holes are needed to identify shaft locations, which requires multiple night time possessions of the railway.
Muon Imaging for Tunnel Engineering Investigations
Using cosmic ray muons for the investigation of tunnel overburden is not new - the earliest reference is its use in the Snowy Dam project in New South Wales, Australia, in 1955. Building on this early, our work has been to mature the technique ready for railway tunnel engineering investigations. Working closely with colleagues from Central Alliance, the Geoptic team imaged the whole length of the Alfreton Old Tunnel, in Derbyshire, England, in around 60 hours using cosmic ray muon imaging; an order of magnitude quicker than conventional methods. In this blind test, the collaborative team resolved one suspected shaft region, saving the client costs in further expensive intrusive drilling tests, and detected a construction shaft in another region, that would require remediation in the long-term.
Click here to read more about our work in the December 2019 Issue of Ground Engineering magazine
The mobile muon imaging system (in the van) within the Alfreton Old Tunnel, Derbyshire, performing a scan of the overburden.
