CASE STUDY: Eden Brows Landslide
Project Name: Eden Brows
Project Type: Rail – Slope Instability
Client Name: Network Rail and Story Contracting
While the Settle-Carlisle Railway was being built in the 1870’s, a landslide occurred on this section of track.
The site is situated on a landslip above the River Eden and below the Settle to Carlisle Railway Line at Eden Brows near Armathwaite, Cumbria. The site is underlain by Devensian Till overlying the Penrith Sandstone Formation and the Pennine Lower Coal Measures Formation.
Boreholes were urgently required on the active slope failure to provide quality site data for the design of remediation measures to enable the re‐opening of the railway line as soon as possible.
Eleven boreholes were required to be formed on the steeply sloping hillside between the river and the railway which contributed to the overall and vast amount of ground investigation works ongoing on site.
The boreholes were to be installed with standpipes, piezometers and inclinometers.
The ground conditions were very difficult with very soft access to the base of the slope.
To facilitate access Storey Contracting constructed a substantial purpose built trackway comprising timber covered with Terram matting and imported roadstone.
Once on the slope the conditions were again challenging being both wet and soft, and covered with branches and tree stumps.
Heavy rainfall in the winter of 2015-16 reactivated part of the existing landslide and caused instability on the slope below the railway line, forcing its closure.
Geotechnical Engineering Ltd provided an award winning P60 slope climbing rig to safely and efficiently form the required boreholes. Due to the active nature of the landslip and poor ground conditions the rig was secured using plate anchors.
The P60 rig provided quality dynamically samples and rotary core, along with carrying out in situ SPT testing to BS EN ISO 22476‐3:2005+A1:2011 and Class 1 UT100 samples.
By utilising the P60 rig the ground investigation successfully delivered quality data for remediation design.
The use of the P60 slope climbing rig avoided the need for any other costly and time-consuming access methods such as scaffolding.
The recovered samples allowed detailed logging and quality material for high-end geotechnical laboratory testing including ring shear, Young’s modulus, Poisson’s ratio and shear strength by direct shear.